Polymer-Driven Fuel Conditioning: A Novel Approach to Improving the Stability and Environmental Performance of Marine Fuels

Abstract

The precise regulation of water content plays a pivotal role in determining several the critical properties of marine fuels, including combustion stability, corrosion resistance, and the mitigation of pollutant emissions. The present study introduces an innovative, additive-free technique for moisture extraction from Marine Gasoil (MGO) utilizing the hydrophilic polymer polyacrylamide, which leverages its polar amino groups to attract water molecules. This process facilitates the physical extraction of moisture without modifying the fuel’s composition, in contrast to traditional drying techniques or chemical additions. Experimental findings indicate a 34.6% decrease in water content in MGO (from 29.3 mg/kg to 19.15 mg/kg) and a 36.5% reduction in MGO–biodiesel blends (from 32.04 mg/kg to 20.34 mg/kg), accomplished within one hour of treatment. The scientific significance of this work lies in its discovery of polyacrylamide’s ability to retain moisture within a nonpolar fuel matrix—a phenomenon not previously investigated in maritime fuel applications. The findings highlight the potential for further research into polymer–fuel interactions and non-chemical strategies for fuel enhancement. Economically, the proposed technology reduces dependence on costly chemical additives and energy-intensive drying processes, while environmentally, it improves combustion efficiency and lowers emissions of hydrocarbons (HC), carbon monoxide (CO), and smoke. Overall, the results introduce a novel, sustainable, and practical process for improving maritime fuel quality, while supporting compliance with increasingly stringent regional and global environmental regulations.

1. Introduction

Moisture contamination is a significant impediment to the efficiency and reliability of marine fuels—particularly biodiesel and distillate blends—since even trace amounts of water can lead to engine corrosion, promote microbial growth, impair combustion quality, and increase emissions of carbon monoxide and particulate matter [1,2,3,4]. The problem is particularly notable in biofuels, which are more hygroscopic compared to conventional fuels. Maintaining low water content is therefore essential to preserve fuel quality and environmental performance. Excess moisture in marine gas oil (MGO) and MGO–biodiesel blends can lead to corrosion of fuel systems, microbial proliferation, ice-related blockages, and combustion inefficiencies, ultimately raising maintenance costs and increasing emissions of particulate matter, unburned hydrocarbons, and greenhouse gases [5,6,7,8,9,10,11]. Handling moisture in marine fuels is thus of high importance, particularly under international institutions such as the IMO 2020 sulfur cap, which aims to reduce the environmental footprint of the shipping industry [12]. In this context, innovative moisture-control technologies are not only essential for operational reliability but also for achieving sustainability targets, aligning with Sustainable Development Goal 13 (Climate Action) and supporting the broader transition toward low-emission maritime transport [7,8,9].

Previous research on marine fuel quality has extensively documented the detrimental effects of water contamination on combustion efficiency, the corrosion of components, and microbial growth within storage and distribution systems [13,14]. These problems are amplified in biodiesel and biodiesel–diesel blends, which are inherently hygroscopic and more prone to oxidation than conventional marine fuels [15,16]. As the maritime sector shifts toward low-sulfur and bio-based fuels to meet international climate commitments and regulatory standards set by the International Maritime Organization (IMO) and the European Union (EU), effective moisture management becomes increasingly critical [12,13,14,15]. Various physical and chemical methods—such as centrifugation, adsorption media, and the use of chemical additives—have been proposed for water removal [16,17]. However, these techniques often suffer from limitations such as high operational cost, energy intensity, or incompatibility with newer bio-based fuel formulations.

Recent advances in polymer science have suggested that hydrophilic polymers can play a significant role in moisture control within liquid fuels and industrial fluids. Studies on polyacrylamide (PAM) and related hydrogels have demonstrated their strong capacity for water adsorption through hydrogen bonding and polar interactions, offering a low-cost, low-energy approach to moisture extraction [18,19]. For instance, polyacrylamide–sodium acrylate hydrogels achieved up to 54% water removal from biodiesel at room temperature [20,21,22], while cellulose–polyacrylamide composites exhibited comparable water-extraction performance [23]. These findings suggest that polymer-based approaches could be adapted for fuel conditioning applications. However, the targeted use of PAM for moisture reduction in marine fuels, particularly in biodiesel-containing blends, remains underexplored.

The present study addresses this gap by introducing a low-energy, additive-free method for moisture reduction in marine fuels using polyacrylamide (PAM), a hydrophilic polymer known for its strong water-binding capacity through polar amide groups. The method relies on physical adsorption rather than chemical modification, allowing the removal of moisture under ambient conditions without altering the intrinsic properties of the fuel. Experimental results demonstrate that PAM treatment reduces moisture content by 34.6% in marine gas oil (MGO) and 36.5% in MGO–biodiesel blends while maintaining compliance with the physicochemical requirements set by ISO 8217 [24]. This establishes PAM as a practical, scalable, and cost-effective solution for on-board or port-based fuel conditioning systems.

The environmental implications of this approach are significant. Reducing water content enhances combustion efficiency and promotes more complete oxidation, thereby lowering emissions of sulfur oxides (SO_x), volatile organic compounds (VOCs), carbon monoxide (CO), and particulate matter (PM)—key pollutants that contribute to air quality degradation and acid deposition in coastal regions [5,6]. Moreover, minimizing moisture content limits microbial growth, which is a major cause of filter clogging and biocorrosion, particularly in humid or variable temperature conditions typical of maritime storage and logistics [12]. Consequently, fuels—especially fatty acid methyl ester (FAME) biodiesel blends—exhibit improved stability, longer shelf life, and greater operational reliability, reducing the frequency of maintenance interventions and associated costs.

From a policy and regulatory perspective, improved fuel quality supports compliance with IMO MARPOL Annex VI sulfur emission standards and the EU Fuel Quality Directive 2009/30/EC, while aligning with the European Green Deal’s climate objectives and Sustainable Development Goal 13. Because the PAM-based method requires no chemical additives and avoids energy-intensive pre-processing, it represents a low-energy and circular approach to maritime fuel management. The proposed technology can thus serve as an enabling solution on the sector’s pathway to net-zero emissions, complementing the introduction of drop-in biofuels and future green-hydrogen derivatives.

Beyond environmental advantages, the method offers clear economic benefits across the marine fuel supply chain. By reducing moisture levels, it enhances combustion efficiency and lowers specific fuel consumption, translating to reduced operational costs per voyage—a crucial consideration in commercial shipping. It also mitigates moisture-induced degradation and component failures, further lowering maintenance and replacement expenses [12,23].

In this context, the present study treats maritime fuel as a regulated and valuable resource, demonstrating that polyacrylamide-based hydrogels provide a sustainable, low-energy, additive-free means of moisture management under ambient conditions. This approach improves resource efficiency across the fuel life cycle by physically adsorbing water without modifying fuel chemistry, thereby stabilizing quality against microbial contamination and corrosion, prolonging shelf life, and enhancing operational reliability. The environmental co-benefits—including lower emissions of SO_x, VOCs, CO, and PM—support regulatory compliance while maintaining ISO 8217 standards [24]. From a governance perspective, the method offers a scalable and regenerable quality-assurance tool that enhances supply-chain resilience and reduces total cost of ownership.

The scientific innovation of this work lies in the direct, non-destructive application of hydrophilic polymers for moisture removal from marine fuels—a technique not previously investigated in maritime contexts. By revealing how intelligent polymer materials can improve maritime fuel quality and promote cleaner, more climate-resilient shipping practices, this study contributes to the advancement of environmental engineering and sustainable fuel technology.

2. Materials and Methods

This study evaluated two representative marine fuels—marine gas oil (MGO), a commonly used distillate in shipping, and biodiesel, a renewable fuel derived from organic feedstocks—to assess the effectiveness of moisture-reduction strategies. Both fuels were treated with polyacrylamide (PAM), a hydrophilic polymer with a high water-binding capacity, to determine its efficiency in reducing water content and improving overall fuel quality. Water content was measured in accordance with ISO 12937 (Karl Fischer titration) for petroleum products [25]. The selection of PAM was guided by its cost-effectiveness, favorable environmental profile, and established applications in water treatment and enhanced oil recovery [26,27]. This approach provides an innovative and scalable method for improving the physicochemical stability and combustion performance of marine fuels under ambient conditions, while contributing to compliance with IMO 2020 [12] sulfur regulations and broader decarbonization goals in maritime transport.

Thermal analysis was performed to assess the behavior of polyacrylamide (PAM) and its interactions with diesel fuel, employing two complementary techniques: thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA meas-urements were conducted using a simultaneous thermal analyzer STA 503 (BAEHR Thermo-Analyse GmbH, Altendorf Straße 12, 32609 Hüllhorst, Germany) under an inert nitrogen atmosphere. The temper-ature was raised from 30 °C to 600 °C at a controlled heating rate of 20 °C/min. During the procedure, mass loss and differential temperature (ΔT) were continuously moni-tored to document thermal decomposition events and moisture release behavior.

Differential scanning calorimetry (DSC) was performed utilizing a temperature-modulated DSC instrument (TA Instruments, Q200, ConneXions Business Park, Brusselsesteenweg 500, 1731 Zellik België, Singapore), calibrated with sapphire for heat capacity and indium for temperature and enthalpy measurements. Samples weighing between 5 and 12 mg were hermetically sealed in TZero aluminum pans and analyzed in a high-purity nitrogen atmosphere. The thermal profile comprised two sequential scans: an initial heating from 20 °C to 200 °C at a rate of 10 K/min, followed by cooling back to 20 °C at 20 K/min, and concluding with a final heating to 250 °C at 10 K/min. This dual-scan method facilitated the identification of thermal transitions, such as moisture evaporation, glass transitions, and the onset of decomposition.

3. Results and Discussion

3.1. Moisture Reduction Procedure Results

The experimental findings are encapsulated in

Table 1. Physicochemical properties of marine gas oil (MGO) determined according to ISO standard methods [24,25,28,29,30,31,32,33], serving as the baseline for evaluating the effects of PAM-based dehumidification on combustion, safety, and environmental performance.

Parameter	Units	Limits	Methods	(MGO)
Density at 15 °C	gr/mL	max 0.8900	ISO 12185:2024 [28]	0.828
Distillation			ISO 3405:2019 [29]
first drop of distillation	% v/v		Reported	180.2
end of distillation	% v/v	Reported	382.4
Distillation temperature 10% recovery	°C	Reported	220.2
Distillation temperature 50% recovery	°C	-	275.2
Distillation temperature 90% recovery	°C	-	348.4
Sulfur Content	mg/kg	max 10,000	ISO 20846:2019 [30]	26.00
Flash Point	°C	min 60	ISO 2719:2016 [31]	67.1
Water Content	mg/kg	max 200.0	ISO 12937 [25]	29.3
Color/appearance	-	Black	VISUAL	Black
Kinematic Viscosity at 40 °C	cSt	2.0–6.0	ISO 3104:2023 [32]	3.017
Cetane Index	-	min 40	ISO 4264:2018 [33]	57.7

Source: Own elaboration.

and

Table 2. Physicochemical properties of biodiesel determined according to ISO standard methods [25,28,30,31,32,34], serving as the baseline for evaluating the effects of PAM-based dehumidification on fuel stability, combustion behavior, and environmental performance.

Parameters	Units	Limits	Methods	Biodiesel
Density at 15 °C	gr/mL	0.860–0.900	ISO 12185:2024 [28]	0.881
Flash Point	°C	min 60	ISO 2719:2016 [31]	175.1
Water Content	mg/kg	max 500.0	ISO 12937 [25]	250.5
Cetane Index	mg/kg	min 51	ISO 5165 [34]	51.5
Kinematic Viscosity at 40 °C	cSt	2.0–6.0	ISO 3104:2020 [32]	3.017
Sulfur Content	mg/kg	10max	EN ISO 20846 [30]	5.2

Source: Own elaboration.

. Table 1 presents the physicochemical properties of the MGO sample assessed in accordance with recognized ISO methods [24,25,28,29,30,31,32,33], establishing the foundation for analyzing the effects of PAM-based dehumidification on combustion behavior, safety, and environmental performance. Table 2 displays the pre- and post-treatment water content for MGO and MGO–biodiesel blends after PAM treatment, facilitating the evaluation of moisture removal effectiveness while confirming that essential attributes adhere to ISO 8217 standards [24]. Comprehending these baseline parameters and post-treatment outcomes is crucial for assessing the viability of incorporating PAM-based conditioning into onboard or port-based fuel quality control.

The recorded density (0.828 g/mL) is much below the maximum threshold of 0.8900 g/mL, demonstrating adherence to specifications and suitability for marine engines. Distillation measurements confirm a wide boiling range (180.2–382.4 °C), indicating the multi-component nature of the fuel and enabling stable combustion and suitable volatility. The sulfur concentration (26.00 mg/kg) is well below the regulation maximum of 10,000 mg/kg, indicating compliance with low-sulfur standards and aiding in the reduction of SO_x emissions. The flash point of 67.1 °C surpasses the 60 °C safety barrier, guaranteeing secure storage and handling during maritime activities. The kinematic viscosity at 40 °C (3.017 cSt) falls within the specified range of 2.0–6.0 cSt, facilitating effective injection and atomization in marine diesel engines. The cetane index of 57.7 significantly exceeds the minimum requirement of 40, indicating excellent ignition quality and optimal combustion efficiency.

The water concentration (29.3 mg/kg) is below the 200 mg/kg threshold but still requires consideration, as excessive water might hinder combustion, elevate corrosion risk, and jeopardize stability. This result prompts the current study of polyacrylamide as a hydrophilic polymer for precise moisture reduction to improve the environmental and operational efficacy of MGO and its biodiesel mixtures.

The subsequent stage of the analysis is presented in Table 2, which summarizes the physicochemical properties of the biodiesel used in the experimental phase, determined using internationally recognized standards (ISO and EN ISO). Characterizing biodiesel is essential for evaluating its compatibility with marine gas oil (MGO) and its suitability for blending to enhance environmental performance and reduce emissions. Together with the MGO baseline data shown in Table 1, these results provide a consistent framework for assessing both the effectiveness and the specification compliance of the proposed polyacrylamide-based dehumidification approach.

The density of biodiesel (0.881 g/mL) falls within the acceptable range (0.860–0.900 g/mL), indicating adequate energy content and good blend compatibility with MGO, whose density is 0.828 g/mL (Table 1). Its flash point (175.1 °C) is substantially higher than that of MGO (67.1 °C), improving handling safety in warm environments and reducing fire risk during storage and transport.

A key concern is the water content of biodiesel (250.5 mg/kg), which exceeds the 200 mg/kg limit. This highlights the need for effective moisture-removal measures, such as the polyacrylamide (PAM) treatment tested here. PAM is a hydrophilic, high–molecular-weight polymer (Mn ≈ 150,000) with strong polarity and water-binding capacity, enabling efficient moisture reduction in both neat fuels and blends. Moisture management is also relevant for MGO, which shows a water content of 29.3 mg/kg (Table 1). Addressing this common limitation provides a cross-compatible pathway to improve the quality and stability of both fuels.

The combustion qualities of biodiesel are adequate: the cetane index (51.5) satisfies the minimal standard (≥51), ensuring dependable ignition. The kinematic viscosity at 40 °C (3.017 cSt) aligns with that of MGO, promoting flow compatibility and efficient atomization in marine diesel injection systems when combined. The sulfur concentration (5.2 mg/kg) is well below the EN ISO 20846 [30] threshold (10 mg/kg), consistent with initiatives to reduce SOₓ emissions and ensuring adherence to IMO 2020 standards [12].

Collectively, Table 1 and Table 2 demonstrate that although MGO and biodiesel possess beneficial fuel properties, both are susceptible to high moisture levels, which diminish combustion efficiency, elevate emissions, and jeopardize storage stability. The experimental use of polyacrylamide provides a scalable, environmentally sustainable option that enhances performance and dependability while facilitating the shift to low-emission maritime transport.

The subsequent graphic illustrates the chemical structure of polyacrylamide (PAM), a commonly utilized hydrophilic polymer consisting of repeated units of acrylamide monomers. The general structure is represented as: [–CH2–CH(CONH₂)]

The polyacrylamide backbone consists of a saturated carbon–carbon chain with pendant amide groups (–CONH₂) as provided in Scheme 1. The pronounced dipole of these amides imparts a significant affinity for water to the polymer: via hydrogen bonding and dipole–dipole interactions, it can adsorb water at available sites and, in cross-linked (hydrogel) form, absorb and hold substantial volumes inside the swelled matrix.

In the fuel-dehydration tests, we recorded the behavior of poly-acrylamide (PAM) when in contact with water-bearing fuel. Scheme 2 illustrates two Petri dishes at different stages: the left displays dry PAM powder (baseline), while the right depicts the polymer after exposure to fuel with dissolved/dispersed water, exhibiting visible swelling and gelation as a result of water absorption. This side-by-side comparison offers qualitative evidence of PAM’s hydrophilicity and moisture-capture capacity through hydrogen bonding and dipole–dipole interactions, thereby complementing the quantitative Karl Fischer measurements. The swollen polymer is physically separable, facilitating straightforward filtration post-treatment and highlighting its utility in fuel dehydration applications.

Polyacrylamide (PAM) is well known for its high water-absorption capacity, primarily attributed to its polar amide functional groups, which readily form hydrogen bonds with water molecules. Its pronounced hydrophilicity has supported extensive industrial use for more than four decades. Initially employed in large-scale water treatment during the 1970s and 1980s, PAM’s applications have since expanded to include pulp and paper production, agriculture, and the oil and gas industry—where approximately 30% of global production is utilized, primarily in enhanced oil recovery (EOR) operations and drilling fluid stabilization [26,35,36].

The polymer’s capacity to absorb water from non-aqueous, hydrocarbon-based matrices such as diesel and biodiesel is increasingly significant in fuel treatment. This study examines the under-researched application of PAM using a straightforward and effective experimental procedure. Polyacrylamide, in its native state, manifests as a white, dry, fine-textured powder. When introduced into a controlled quantity of fuel—Marine Gasoil (MGO) or biodiesel—it undergoes a physical transformation, absorbing moisture present in the fuel and forming a clumped, gel-like structure. The post-treatment form observed in the experimental setup demonstrates both the polymer’s efficacy in water removal and its physical stability in fuel-rich, nonpolar conditions.

The observed discoloration of the gel following contact with the fuel is likely due to mild interactions with organic compounds found in biodiesel or MGO, supporting the hypothesis that PAM functions through physical adsorption rather than chemical reaction. This trait is advantageous, as it guarantees that fuel quality and composition are preserved after treatment. The qualitative findings correspond with the quantitative reductions in moisture content observed in the study, indicating moisture removal efficiencies exceeding 30%, without negatively affecting other critical physicochemical parameters, including viscosity, density, cetane index, or sulfur content.

3.2. Thermographic Analysis Results

As mentioned in the methodology section and in order to validate the behavior of PAM in the newly formatted environmental conditions, the polymer underwent analysis via Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). The first method, namely DSC facilitated the evaluation of thermal transitions and potential interaction energies, whereas TGA offered insights into the decomposition profile and water retention capacity under a controlled temperature gradient. The experiments demonstrated that PAM exhibits consistent thermal stability when exposed to fuel and confirmed its ability to retain absorbed moisture under standard handling conditions. Weight losses associated with the release of absorbed water occurred within the anticipated temperature range for PAM desorption [35].

The findings of the whole process as well as the implications in scientific economic and environmental aspects will be further analyzed in the next section.

3.2.1. TGA Thermographic Analysis Results

The first procedure, that is Differential scanning calorimetry (DSC) was performed utilizing a temperature-modulated DSC instrument (TA Instruments, Q200), calibrated with sapphire for heat capacity and indium for temperature and enthalpy measurements. Samples weighing between 5 and 12 mg were hermetically sealed in TZero aluminum pans and analyzed in a high-purity nitrogen atmosphere. The thermal profile comprised two sequential scans: an initial heating from 20 °C to 200 °C at a rate of 10 K/min, followed by cooling back to 20 °C at 20 K/min, and concluding with a final heating to 250 °C at 10 K/min. This dual-scan method facilitated the identification of thermal transitions, such as moisture evaporation, glass transitions, and the onset of decomposition.

The thermal characterization of neat PAM identified three significant degradation zones in the TGA thermogram. The initial zone, ranging from 25 to 110 °C, is associated with the evaporation of physically adsorbed water. The second weight-loss region, occurring between 248 and 345 °C, is ascribed to cyclization reactions involving the amide groups of PAM, which release ammonia and result in the formation of imide structures. The third and most critical degradation phase commences at approximately 350 °C, associated with the decomposition of the polymer backbone and the transformation of imide groups into nitriles, leading to the breakdown of the structure into volatile hydrocarbons. These findings are consistent with previous research on polyacrylamide thermolysis, encompassing iridization mechanisms and multi-step degradation pathways [15,16,17,18,19,20,21,37].

The PAM–diesel mixture demonstrated only two main degradation events. The initial degradation phase commenced at around 186 °C, presumably indicating the evaporation of diesel, water, and remaining volatile substances, leading to a substantial mass reduction of approximately 80%. The second step, occurring at approximately 410 °C, involves the gradual thermal degradation of the residual polymeric material, resulting in an additional 11% mass loss. The PAM–diesel sample exhibited a total mass loss of approximately 91%, which is notably greater than the 71% recorded for neat PAM. The heightened volatility is linked to the combined effects of diesel adsorption and polymer decomposition, underscoring PAM’s efficacy as a water-binding agent in fuel systems. The DSC scans of PAM–diesel exhibited broad endothermic transitions in the low- to mid-temperature range, indicative of energy absorption associated with phase change and moisture desorption.

These results confirm the capacity of PAM to effectively bind and later release moisture and hydrocarbons under controlled thermal conditions. The differences in degradation pathways between neat and fuel-loaded PAM highlight the polymer’s compatibility with hydrocarbon systems and its potential utility in enhancing fuel stability during storage and transport. This supports its application as a low-cost, reusable, and environmentally benign method for controlling water contamination in fuel systems, particularly in the marine sector where fuel quality is tightly regulated. The findings also provide a valuable thermal and kinetic framework for future work aimed at optimizing PAM-based fuel purification technologies [38,39,40,41].

Scheme 3 depicts the cyclization reaction mechanism of polyacrylamide (PAM) under thermal conditions, a critical process influencing its thermal degradation behavior. Heating induces intra-molecular condensation of adjacent amide groups in the polymer backbone, leading to the formation of a five-membered imide ring and the concurrent release of ammonia (NH₃). This reaction generally takes place within a temperature range of 240–350 °C, as evidenced by thermogravimetric (TGA) and differential scanning calorimetry (DSC) data.

This cyclization pathway is important for understanding the thermal stability and decomposition characteristics of PAM, particularly in composite systems such as PAM–diesel mixtures. The formation of stable cyclic imide structures signifies the transition from physical changes, such as moisture evaporation, to chemical degradation, which ultimately affects the polymer’s reusability, structural integrity, and compatibility with hydrocarbon fuels. This mechanistic insight informs the design of moisture-absorbing additives that sustain performance under operational thermal loads.

The significant volume of literature supporting this mechanism includes references [15,16,17,18,19,20,21,22,23], which have thoroughly characterized the iridization behavior of polyacrylamide and its thermal conversion products.

The thermogravimetric analysis (TGA) curve as illustrated in Figure 1 compares the thermal degradation behavior of pure polyacrylamide (PAM) with that of a PAM–diesel composite, highlighting distinct differences in their stability and decomposition pathways.

In the case of pure PAM, the first degradation stage is taking place between 25 °C and 110 °C, with a mass loss of about 7%, attributed to the evaporation of physically adsorbed water. This behavior reflects PAM’s strong affinity for moisture due to its hydrophilic amide groups. The second stage, observed between 250 °C and 350 °C, results in an additional ~13% mass loss, primarily associated with ammonia release during polymer cyclization. The most significant degradation step, accounting for approximately 61% mass loss, occurs near 350 °C as imide groups decompose and the polymer backbone undergoes scission, yielding long-chain hydrocarbons.

By contrast, the PAM–diesel composite exhibits a much more pronounced early mass loss of ~80% between 100 °C and 300 °C. This sharp decline is attributed to the evaporation of diesel constituents, moisture, and partially degraded polymer chains. A subsequent degradation stage between 400 °C and 500 °C produces an additional of 11% mass loss, probable due to the combustion of residual polymeric material and volatile byproducts. Overall, the PAM–diesel composite experiences substantially greater mass loss than pure PAM, indicating that diesel absorption accelerates decomposition and diminishes thermal stability with higher speed.

In terms of economic perspective, the findings indicate that PAM provides a low-cost and efficient method for removing moisture from diesel-based fuels. Its high capacity to absorb both fuel and water at relatively low temperatures demonstrates its potential as a practical approach to improving fuel quality prior to use—particularly in industrial and maritime applications where moisture contamination poses significant challenges. PAM is alluring due to dehydration because it is low-cost, reusable, and in most cases compatible with existing filtration systems. Moreover, avoiding thermal treatments during crude fuel processing preserves the fuel’s intrinsic properties while simultaneously reducing energy consumption and overall operational costs.

The ability of PAM to hold onto water and improve the efficiency of fuel combustion has also environmental impacts. The aforementioned approach improves combustion efficiency by decreasing the moisture content, which in turn reduces the amount of harmful pollutants released, including sulfur oxides (SO_x), carbon monoxide (CO), and unburned hydrocarbons. The specific results contribute significantly to global sustainability goals, as synopsized in SDG 13 (Climate Action), while at the same time the fuel quality standards set by the International Maritime Organization and the European Commission’s Green Deal goals are met. What is more, PAM is not related to dangerous waste production, and it can be thermally regenerated, satisfying the rules and modes of circular economy in fuel processing. The results thus unveil the technical, economic, and environmental advantages of incorporating polyacrylamide into modern fuel treatment methodologies.

3.2.2. DSC Analysis Results

The glass transition temperature (Tg) is a key thermophysical property used to characterize polymeric materials, representing the temperature range over which a polymer transitions from a rigid, glassy state to a more flexible, rubber-like phase. In this study, Differential Scanning Calorimetry (DSC) was employed to determine the Tg of both neat polyacrylamide (PAM) and the PAM–diesel composite. As shown in Figure 2, the Tg of pure PAM was recorded at 179 °C, which aligns well with literature values for high–molecular weight PAM exhibiting strong hydrogen bonding and limited segmental mobility [20].

The PAM–diesel composite had a markedly lower Tg of around 163 °C, suggesting that diesel facilitates molecular-level plasticization effects. This alteration is likely due to the formation of hydrogen bonds or dipole interactions between the polar functional groups of PAM (mostly the –CONH₂ amide groups) and the partially polar components of diesel, which can engage with the polymer network. These interactions disrupt the intra- and intermolecular hydrogen bonding in PAM, enhancing the mobility of the polymer chains and thereby lowering the Tg. This observation corresponds with research indicating that the incorporation of plasticizers or solvents into polymer matrix enhances free volume and segmental mobility [20,21,22,23,24,25,26,27,35,36,37].

The reduction in Tg signifies that PAM, when exposed to diesel, becomes less rigid and more flexible, which may influence its long-term thermal and mechanical stability. This softening may boost the polymer’s adaptability in filtration and absorption systems, as increased flexibility promotes more efficient interaction with fuel molecules. Nonetheless, it necessitates careful assessment in high-temperature applications, where diminished thermal resistance may be a limitation.

Figure 2 illustrates the Differential Scanning Calorimetry (DSC) thermograms of pure polyacrylamide (PAM) and a PAM–diesel composite, represented as heat flow (W/g) vs. temperature (°C). This study investigates the thermal transitions of the samples during the second heating scan, focusing specifically on the glass transition temperature (Tg), which is critical for evaluating polymer flexibility and thermal performance.

The glass transition temperature (Tg) of the unadulterated PAM sample (black curve) is recorded at around 179 °C. This number signifies a highly hydrogen-bonded, structurally rigid polymer network, in which strong intermolecular forces restrict the mobility of polymer chains. The sudden shift at this temperature marks the glass-to-elastic transition, reflecting enhanced molecular mobility within the material.

In contrast, the red curve representing the PAM–diesel sample displays a decreased Tg of around 163 °C. The reduction in the glass transition temperature indicates that the interaction between the PAM matrix and diesel fuel results in plasticization. Diesel components, containing polar or aromatic hydrocarbons, likely disrupt the internal hydrogen bonding of the PAM chains, so increasing their segmental mobility and decreasing the energy required for the glass-to-rubber transition. This is evidenced by the more pronounced and nuanced transition in the red curve.

The decrease in Tg within the PAM–diesel system signifies that the polymer demonstrates diminished stiffness and enhanced flexibility after diesel absorption. This softening may enhance the polymer’s ability to adapt to and retain fuel impurities or moisture. However, the diminished Tg also indicates a drop in the material’s thermal resistance, which may impact its performance in high-temperature situations.

This observed alteration is in line with findings in the literature about polymer-solvent interactions, where foreign compounds act as plasticizers. Thermal changes are crucial for assessing the long-term viability of PAM in hydrocarbon fuel systems, particularly in moisture removal processes, since they influence physical attributes, durability, and regeneration potential [14,15,16,17,18,19,20,21,22,23,24,25,26,27,35,36,37,38,39].

The DSC thermograms demonstrate that diesel absorption significantly alters the thermal properties of PAM. This enhances flexibility and interaction with fuel matrices; however, it may necessitate additional stabilizing methods if thermal resilience is required for repeated use or harsh operating conditions.

A well-organized parametric analysis was conducted to improve and validate the effectiveness of polyacrylamide (PAM) in moisture extraction from diesel fuel. The study validated that PAM interacts with the fuel matrix and physically absorbs water, as seen by its removal through filtering after exposure, and further investigated the influence of key variables on the dehydration process. The impacts of polymer residence time in the fuel, the amount of PAM provided, and the volume of treated gasoline were systematically analyzed. The specific effect of each factor on moisture reduction was assessed by keeping two of the three variables constant in each trial. This is realized the identification of optimal operational parameters for maximum water extraction efficiency. The results of this experimental analysis are illustrated in Figure 3.

As illustrated in Figure 3, it becomes evident that moisture removal from MarinGasoil (MGO) using polyacrylamide (PAM) is most efficient at an approximate contact time of 60 min, given the lowest recorded water content (19.15 mg/kg) recording a reduction of nearly 35% compared to the untreated sample. This finding has not only scientific but also significant economic implications. More specifically, by optimizing the process to a one-hour treatment, industries may well reduce the quantity of PAM required, minimize energy consumption related to processing time, and improve the overall efficiency of fuel conditioning operations.

Moisture in fuels such as MGO and biodiesel can lead to poor combustion, reduced energy output, increased maintenance costs, and corrosion in storage and engine systems [1,2,3,4,5]. By mitigating these issues through effective dehydration, operators can extend engine life, reduce unplanned maintenance, and lower operational costs associated with equipment failure. Moreover, improved combustion efficiency directly translates into better fuel economy and reduced emissions of harmful pollutants such as carbon monoxide (CO), unburned hydrocarbons, and particulate matter, aligning with international marine fuel standards (IMO 2020 regulations) [12] and contributing to compliance with environmental legislation like the European Green Deal and SDG 13 (Climate Action).

In terms of cost, evidently the use of PAM is cost-effective. More specifically, with an estimated market price of approximately €2.5 per kilogram, and a dosage of 0.1 g per 20 mL of fuel as used in this study, the treatment cost remains low compared to the economic benefits achieved. The ability to recycle or reuse PAM in multiple cycles, as noted in prior research, further enhances its economic viability. Additionally, its application is not in need of major infrastructure changes, making it accessible for both small-scale operations and large industrial settings [25,26,27,35,36,37,38].

To ensure that the incorporation of polyacrylamide (PAM) into MarinGasoil does not affect in a negative way its efficacy in combustion engines, it was more than necessary to estimate the potential effects on critical physicochemical properties. Although the polymer effectively removes moisture, the fuel must nevertheless comply with specified requirements for safe and efficient engine running. Therefore, a thorough array of physicochemical properties was assessed prior to and subsequent to PAM treatment. The results, depicted in Figure 4, provide essential insights into compatibility and safety in terms of the operation of the suggested strategy.

The left panel of Figure 4 presents the experimental flow for applying PAM to marine gas oil (MGO), including the polymer’s introduction, interaction time, and removal via filtration. The top right panel compares key physicochemical properties of MGO before and after PAM treatment, demonstrating negligible variation in properties such as density, viscosity, sulfur content, and flash point, while showing a significant reduction in water content. The bottom right panel illustrates the trend of water content over different residence times, highlighting the optimal reduction (~34.6%) achieved around 60 min.

This present study confirms that polyacrylamide, used as a hydrophilic addition, markedly reduces moisture in naval gas oil without altering the essential characteristics of the fuel. The most substantial decrease in humidity occurs within the first hour, signifying a rapid binding affinity between the polymer and water molecules. This outcome is significant for both the economy and the environment. Reducing the water content enhances combustion efficiency, prolongs engine lifespan, decreases maintenance costs related to corrosion, and diminishes emissions of deleterious pollutants such as CO, SOₓ, and VOCs. The method is an economical, scalable, and non-intrusive means of integration into fuel supply chains. It is in line with the regulations for clean shipping, the European Green Deal, and Sustainable Development Goal 13 (Climate Action).

The effectiveness of polyacrylamide (PAM) in reducing moisture in traditional marine fuels prompted further investigation into its possible use in the production and treatment of alternative fuels, especially biodiesel. Biodiesel is a renewable fuel derived from vegetable oils, repurposed cooking fats, or animal fats. It mostly consists of fatty acid methyl esters (FAMEs), derived from 10 to 14 different types of fatty acids, contingent upon the feedstock and its processing method [40,41,42,43,44,45,46,47,48].

Biodiesel exhibits significantly greater hygroscopicity compared to petroleum-derived fuels. Water contamination is a widespread issue that can occur in either dissolved moisture or suspended droplets. The pollution levels typically exceed three times those found in standard diesel. The elevated water content diminishes combustion efficiency and storage stability, accelerates microbial proliferation, and initiates degradation processes such as hydrolysis and oxidation, hence impairing fuel quality and engine performance.

Eliminating water from biodiesel using traditional methods—such as heat evaporation, centrifugation, and fine-particle filtration—demands substantial energy, time, and financial resources, particularly when conducted on a big scale. Utilizing PAM could be a transformative alternative. It can efficiently control moisture with minimal energy and cost, as its polar amide groups can physically bind water through hydrogen bonding. If this approach can be refined for biodiesel processing, it may simplify current drying technologies and enhance the commercial viability of biodiesel as a sustainable transport fuel.

PAM treatment enhances water management in biodiesel, aligning with various sustainability objectives, including reducing production costs, minimizing energy use, and ensuring environmental compliance. These advantages directly support regulatory frameworks such as the Renewable Energy Directive (RED II) and Sustainable Development Goals 7 (Affordable and Clean Energy) and 13 (Climate Action), while facilitating the transition to more sustainable transportation networks on land and at sea.

The identical experimental procedures applied to the marine gas oil fuel were also conducted for the 10% marine gas oil and biodiesel blend. We investigated the potential of 0.1 g of polyacrylamide (PAM) in 20 mL of a 10% marine gas oil and biodiesel mixture to reduce humidity levels. The outcomes are illustrated in Figure 5.

The bar graph in Figure 5 shows changes conducted in important fuel quality factors such density, distillation temperatures, sulfur content, flash point, water content, viscosity, and cetane index. Based on the above it is noticeable that PAM treatment drastically lowered the water content without changing other significant fuel properties.

To be more concise the results unveil that polyacrylamide (PAM) treatment managed to minimize the water content in a biodiesel–MarinGasoil 10% blend from 32.04 mg/kg to 20.34 mg/kg. This decrease is very important given that an increased quantity of water in biodiesel may well lead to incomplete combustion, higher emissions of unburned hydrocarbons, microbial development, and corrosion of fuel systems and storage infrastructure [38,39,40,41,42,43,44,45,46,47,48,49]. PAM can also improve combustion efficiency by improving moisture handling. his enhances engine reliability and longevity, which is particularly critical in marine applications where equipment downtime incurs substantial operational costs.

This method offers a strong cost–benefit advantage from an economic perspective. The PAM-based approach is low-cost, easily scalable, and fully compatible with existing fuel handling and processing systems. In contrast, conventional water-removal techniques—such as thermal drying, centrifugation, or the use of chemical desiccants—require significant energy input, specialized equipment, or costly reagents. Polyacrylamide is inexpensive, environmentally safe, and, in some cases, reusable [50,51,52]. For instance, one kilogram of PAM costs only a few euros and is highly effective at minimal dosages, making it suitable for large-scale applications such as refineries, storage facilities, and onboard ship treatment systems.

From an environmental perspective, enhanced moisture control not only mitigates equipment degradation but also reduces emissions of particulate matter, carbon monoxide (CO), and hydrocarbons (HC) associated with incomplete combustion [1,7,8,9,10,11,12,13]. Moreover, by improving the stability and performance of biofuel blends, this approach facilitates the wider adoption of renewable fuels in alignment with global climate objectives. It directly supports the goals of the European Green Deal and the United Nations Sustainable Development Goals—specifically SDG 7 (Affordable and Clean Energy), SDG 12 (Responsible Consumption and Production), and SDG 13 (Climate Action)—by strengthening the viability of bio-based fuels as clean, efficient, and reliable alternatives to petroleum-derived fuels [51,52].

In summary, the application of PAM for moisture removal in biodiesel blends is not only scientifically and technically robust but also economically and environmentally advantageous. It promotes cleaner combustion, reduces maintenance costs, and contributes to the transition toward low-emission and sustainable marine transportation.

4. Conclusions—Future Research

The present work presents a novel and cost-effective method, with potential to expand, for reducing moisture content in both conventional and renewable diesel fuels—particularly Marine Gasoil (MGO) and biodiesel blends—with the assistance of high-molecular-weight polyacrylamide (PAM). Recent surveys have validated that existence even in trace quantities moisture in fuels is a critical issue, leading to incomplete combustion, engine corrosion, microbial contamination, and fuel degradation, especially in hygroscopic biofuels. The proposed PAM-based treatment effectively mitigates these issues by physically adsorbing water molecules through their hydrophilic amide groups, thereby improving overall fuel quality without altering chemical composition or energy content.

The method’s advantages are multiple. Technologically, it is simple, non-destructive, and compatible with existing fuel processing and filtration systems. Economically, it is viable at large scale—given the low cost of PAM (≈€500 per 200 kg) and its high efficiency at minimal dosage (e.g., 0.1 g per 20 mL of fuel)—and further enhanced by the polymer’s recyclability. Environmentally, lowering fuel moisture enhances combustion efficiency, reduces emissions of SO_x, CO, unburned hydrocarbons, and particulates, and aids compliance with IMO 2020 [12] sulfur regulations and global sustainability targets such as SDG 9 (Industry, Innovation and Infrastructure) and SDG 13 (Climate Action).

From a resource-management perspective, the approach promotes sustainability through

• Resource efficiency—achieving moisture reduction under ambient conditions with minimal energy input compared to heat-based drying.
• Compliance and governance—supporting adherence to international and EU fuel-quality and emission standards.
• Economic benefits—reducing corrosion, maintenance costs, and service interruptions across the fuel supply chain.
• Circularity and life cycle performance—enabling polymer reuse and integration with existing filtration infrastructure.
• System resilience—stabilizing biodiesel blends and maintaining fuel integrity during storage and transport.

The particular attributes establish PAM-based fuel conditioning as a promising, low-energy solution bridging materials science, fuel technology, and sustainable resource policy. This particular approach enhances combustion performance and emission control while promoting circular and environmentally responsible fuel management practices.

Nevertheless, more research is needed to optimize polymer–fuel interaction dynamics, assess long-term stability, and validate the method across a broader range of fuel types and humidity conditions. Future studies should also explore continuous-flow or filter-integrated PAM systems, alongside life cycle (LCA) and techno-economic (TEA) evaluations to determine full-scale industrial feasibility.

To synopsize, this work establishes a novel polymer-based strategy for fuel dehumidification—combining technological innovation with economic and environmental sustainability. It represents a meaningful step toward cleaner, more efficient, and resilient fuel systems aligned with global decarbonization and energy-transition objectives.