Purification doi: 10.3390/purification2040016

Authors: Monika Gwadera Dominika Boroń Alicja Misala Maria Radek

This study investigates the adsorption of the textile dye Direct Blue BR 200 from aqueous solutions onto waste chicken eggshells, evaluated as a low-cost biosorbent, and the commercial activated carbon Sorbotech LGCO 100, used as a reference sorbent. Adsorption equilibrium was determined experimentally and interpreted using the Henry, Langmuir, Freundlich, Sips and modified BET isotherms. Among these models, the Sips isotherm provided the best fit for both adsorbents, indicating surface heterogeneity and a finite sorption capacity. The equilibrium data showed that eggshells exhibit higher dye uptake than activated carbon across the investigated concentration range. Kinetic studies were performed in a continuous-flow fixed-bed system at flow rates: 1.72, 2.31 and 2.90 cm3/s. Apparent effective diffusion coefficient (Ds) was determined using the analytical solution to Fick’s unsteady-state diffusion equation. The Ds values obtained for eggshells—2.55 × 10−11 m2/s, 4.59 × 10−11 m2/s, and 1.92 × 10−10 m2/s—consistently exceeded those for activated carbon. The combined equilibrium and kinetic analyses, supported by the calculated diffusion coefficients, demonstrate that waste eggshells outperform the activated carbon Sorbotech LGCO 100 in their ability to adsorb Direct Blue BR 200 from water. The results provide quantitative parameters for modeling adsorption processes and highlight the potential of eggshell-based biosorbents in water treatment applications.

Purification doi: 10.3390/purification2030015

Authors: Shabana Ashraf Samreen Nazeer Aiman Nazir Muhammad Zubair Akram

Freshwater contamination has become a critical global challenge, driven by industrialization, urbanization, agriculture and climate change, threatening safe drinking water and sustainable development. This review synthesizes peer-reviewed literature identified through targeted searches of major bibliographic databases, including Scopus, Web of Science Core Collection and PubMed, with Google Scholar used as supplementary search tool, using contaminant- and technology-specific keywords. Conventional treatment processes, including coagulation–flocculation, sedimentation, filtration, adsorption, activated carbon, ion exchange and chemical disinfection, are critically evaluated alongside advanced technologies such as membrane filtration, reverse osmosis, nanofiltration, advanced oxidation processes (including photocatalysis), electrochemical treatment and nanotechnology-based systems, with emphasis on mechanisms, removal efficiency and operational limitations. Evidence indicates that adsorption-based technologies (GAC/PAC) achieve up to 97% removal of long-chain PFAS following advanced regeneration, coagulation–sedimentation removes up to 95% of microplastics, and precipitation-based processes achieve 70–99% removal of heavy metals, yet no single technology addresses the full contaminant spectrum across varying water quality conditions. Integrated multi-barrier systems combining conventional and advanced technologies therefore provide the most effective and sustainable approach for producing safe drinking water. The review also examines emerging trends, including smart water treatment systems, advanced functional materials, renewable energy integration, and circular water management and identifies key research gaps and priorities for cost-effective, energy-efficient and resilient purification technologies essential to global water security and supporting the achievement of Sustainable Development Goal 6 (Clean Water and Sanitation).

Purification doi: 10.3390/purification2030014

Authors: Johannes König Benedict Montau Marc Wichern Rita Hilliges

Moving bed biofilm reactors (MBBRs) are well established for wastewater treatment. While BOD/COD removal is a typical application, MBBRs are also used for nitrogen elimination, as well as secondary and post-treatment. Due to the robustness of the biofilm, MBBRs are especially suitable for low water temperatures and for challenging conditions. Despite the many benefits of MBBRs, the potential for microplastic emissions caused by constant abrasion of the implemented carriers is often discussed. Direct measurements are not possible due to only minimal material loss in combination with great variations in initial carrier weight. Therefore, the influent and effluent of full-scale MBBRs for municipal wastewater were sampled and analysed for concentrations of polyethylene, polypropylene and styrene–butadiene rubber. Furthermore, different experiments were conducted in lab-scale reactors in order to gain data for an estimation of the actual material loss of the MBBR carriers. The results show that a material loss in the range of 101–102 µg/L can be observed but the microplastic concentrations caused by the MBBR carriers were negligible compared to the overall microplastic concentrations in the inflow of sampled wastewater treatment plants, which were in the range of 103–104 µg/L.

Purification doi: 10.3390/purification2030013

Authors: Kristina Gartsiyanova

This study investigates the impact of critical raw material mining and processing on surface water quality within a representative catchment area, using the Luda Yana River Basin in Southern Bulgaria as a case study. Water quality was evaluated using the Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI), based on data collected from five monitoring stations. The analysis focused on key heavy metals, including Cu, Zn, Pb, Cd, Fe, Mn, Ni, and As, reflecting the influence of both active and historical mining activities in the region. Index values were calculated for the period 2008–2024 and revealed considerable temporal variability and pronounced spatial differences in water quality along the river course. This study provides one of the first long-term integrated assessments of heavy-metal-related water quality in a mining-impacted river basin in Bulgaria using the CCME WQI framework and offers new evidence on the cumulative effects of historical and ongoing mining activities on surface waters. The calculated CCME WQI values ranged from very low levels indicating poor conditions to moderate values corresponding to marginal and, occasionally, fair conditions. Overall, the predominant water quality categories were “poor” and “marginal.” The results demonstrate that the waters of the studied river basin remain below the thresholds for “fair” physicochemical status as defined by the European Water Framework Directive (2000/60/EC) and the corresponding Bulgarian legislation, including Regulation No. H-4/2012 on surface water characterization and the 2010 Ordinance on environmental quality standards for priority substances and certain pollutants. The findings highlight the persistent anthropogenic pressure exerted on the river system and emphasize the need for improved water management strategies. The study further underlines the importance of integrating environmental protection measures into the exploitation of critical raw materials in order to balance economic development with the sustainable management of water resources.

Purification doi: 10.3390/purification2030012

Authors: Vasiliki Alexiou Eirini Zagoraiou Anastasia Maria Moschovi Iakovos Yakoumis Michail Chalaris

The rapid expansion of hydrogen technologies has intensified the demand for platinum group metals (PGMs), particularly platinum (Pt) and iridium (Ir). Proton exchange membrane fuel cells (PEMFCs) and proton exchange membrane water electrolyzers (PEMWEs) rely on PGMs and fluoropolymer membranes such as Nafion, generating increasing volumes of end-of-life (EoL) membrane electrode assemblies (MEAs). Conventional recycling routes are often energy-intensive, hazardous and limited in polymer recovery. In this study, a closed-loop hydrometallurgical recycling route is assessed through a life cycle assessment (LCA), supported by primary experimental data from optimized recycling trials. Mechanical delamination enabled separation of catalyst layers while preserving membranes, followed by a chlorine-based hydrometallurgical process operating under mild conditions. Leaching efficiencies exceeded 99% for Pt and 80% for Ir, demonstrating the feasibility of metal recovery. Two LCA models were developed: (i) a gate-to-gate recycling model for EoL MEAs and (ii) a cradle-to-gate manufacturing model comparing virgin and recycled Pt. Results showed that substituting virgin Pt with recycled Pt reduced the global warming potential of MEA manufacturing by up to 70%. The analysis also identified electricity demand and Nafion membrane waste as key environmental hotspots. Overall, the study highlights the potential of closed-loop recycling to enhance circularity in hydrogen technologies.

Purification doi: 10.3390/purification2030011

Authors: Omobolaji Ayeseni Catherine B. Almquist Jason A. Berberich Neil D. Danielson

Per- and polyfluoroalkyl substances (PFAS) such as perfluorooctanoic acid (PFOA) persist in aquatic environments due to their extremely strong C–F bonds and high environmental stability/poor biodegradability, creating an urgent demand for high-performance and scalable adsorption treatment technologies. This study reports the synthesis, characterization, and fixed-bed column adsorption performance of a dual-polymer-modified activated carbon adsorbent engineered for enhanced PFAS capture. Activated carbon (AC) was sequentially functionalized with polyethyleneimine (PEI) and poly(chlorotrifluoroethylene–co-vinylidene fluoride) (Kel–F) to form the fluorine-rich, amine-grafted composites AC–PEI–KelF and AC–PEI–KelF–PEI. Surface-area studies of the modified AC adsorbents showed a reduction in surface area of about a factor of two, possibly due to pore blockage by the polymers. Continuous-flow column breakthrough studies demonstrated dramatic improvements in perfluorooctanoic acid (PFOA) removal efficiency, with 50% maximum breakthrough time increasing from 80 min for AC to 540 min for AC–PEI–KelF and 1500 min for the AC–PEI–KelF–PEI formulation. Thomas model adsorption capacities for AC, AC–PEI–KelF and AC–PEI–KelF–PEI were, respectively, 65, 490, and 1130 mg/g. The adsorption mechanism, using selective mobile phases, was shown to be due to a combination of electrostatic and hydrophobic/fluorophilic interactions. Kinetic analysis showed that adsorption exhibited pseudo-second-order behavior, with multi-stage intraparticle diffusion. The optimized composite also exhibited strong regeneration stability, retaining 79% performance after six adsorption–desorption cycles, and displayed high selectivity for PFOA, even in the presence of structurally related competitors such as octanoic acid. The adsorption of perfluoropentanoic acid and undecafluoro-2-methyl-3-oxahexanoic acid (GenX) was also significant, and some interaction with trifluoroacetic acid was noted.

Purification doi: 10.3390/purification2030010

Authors: Vasileios M. Pappas

Purification systems in water treatment, gas upgrading, bioprocessing, pharmaceuticals, and resource recovery operate under disturbances that expose the limits of static design and end-point analytics. The central question is no longer whether a model can reproduce historical data, but whether the process can infer its internal state early enough to protect purity, recovery, productivity, and robustness. This critical review examines how purification is moving from monitoring toward self-optimizing operation through process analytical technology, operando sensing, chemometrics, soft sensors, digital shadows, digital twins, hybrid models, and control-oriented optimization. Distinct from recent platform-specific or method-specific reviews, it compares membranes, adsorption and cyclic gas separations, chromatography, and integrated purification trains through the operational chain that links measurement, state estimation, model updating, decision support, and closed-loop action. The review also provides a cross-platform maturity framework and minimum reporting expectations for operational claims. The strongest published operational evidence remains concentrated in continuous downstream bioprocessing, while membrane and adsorption systems contribute major advances in fouling inference, adaptive surrogates, and state estimation. The review concludes by defining the evidentiary conditions required for trustworthy self-optimizing purification.

Purification doi: 10.3390/purification2030009

Authors: Teddy Roy Binetou Diawara Georgette Estephane Joy Alakari Pascal Blanchard Line Poinel Mathilde Lauzent Marie Hubert-Roux Hélène Lavanant Carlos Afonso Carole Lamonier

This study explores deep eutectic solvents (DESs) as potential alternatives to dimethylformamide (DMF) for extractive desulfurization of gas oil and marine fuel oil. A series of DESs, based on choline chloride (ChCl) and tetrabutylammonium bromide (TBAB), were evaluated using straight-run gas oil (SRGO) and compared to DMF. The influence of an oxidation pre-treatment and water content was also investigated, and the most efficient systems were further applied to marine fuel oil. Firstly, oxidation was found to be essential to enhance sulfur removal by improving the extractability of sulfone compounds. The results show that DES formulation strongly affects desulfurization performance, with TBAB-based DESs achieving efficiencies comparable to DMF (~80% desulfurization rate) and outperforming ChCl-based systems. In ChCl-based DESs, a moderate water content (~10 wt%) improved performance, whereas higher amounts disrupted the hydrogen-bond network, as evidenced by Fourier-transform infrared spectroscopy, leading to a decreased efficiency. When applied to marine fuel oil, similar trends were observed, although lower desulfurization levels were obtained due to the complexity of the feed, and a solvent-to-fuel ratio of 5:1 was required for proper phase separation. Fourier transform mass spectrometry analyses highlighted the persistence of refractory sulfur species, emphasizing the need for tailored solvent design. Overall, DESs represent promising and adaptable alternatives for desulfurization processes.

Purification doi: 10.3390/purification2020008

Authors: Marina Mitova Mariya Dushkova Apostol Simitchiev Ivan Bakardzhiyski

In this study, the potential of extrusion for producing functional food from corn semolina enriched with an ultrafiltration (UF) retentate obtained from rose wastewater was investigated. Extrudates were produced using a single-screw laboratory extruder (Brabender 20DN), and their physical (expansion ratio, bulk density, and moisture content), functional (water absorption and solubility indices), and process characteristics (specific mechanical energy and mass flow rate) and phenolic content were investigated. The effect of the UF retentate’s amount (4 or 11%), the temperature in the third zone of the extruder (150 or 170 °C), and the working screw speed (180 or 220 min−1) on the physical, functional and process characteristics was examined using a full factorial design. Increasing the retentate’s amount led to a decrease in the expansion, water solubility index, specific mechanical energy, and mass flow rate, as well as an increase in the bulk density, moisture content, and water absorption index of extrudates. The augmentation of temperature led to a decrease in the bulk density, water solubility index, specific mechanical energy, and mass flow rate and had no significant effect on the other characteristics. The increase in the screw speed resulted in extrudates with a lower water solubility index, water absorption index, and specific mechanical energy and a higher expansion and moisture content, while it had no significant effect on the density and mass flow rate. The UF retentate enhanced the total phenolic, phenolic acid, and flavonoid contents of the extrudates. Optimal conditions for producing high-quality extrudates were found at 5.02% UF retentate, 150 °C, and 207.8 min−1.

Purification doi: 10.3390/purification2020007

Authors: Tianchen Hu Santanu Saha Yohei Asada Yasuhisa Adachi

The flow behavior of montmorillonite (MMT) slurries with a volume fraction of 6.6×10−4 to 1.6×10−3, coagulated in 1.0 M NaCl, was investigated across laminar, transitional and turbulent regions using a closed-loop circular pipeline system equipped with dual pressure transducers and a flow meter. In the laminar region, the linearized approximation of the Bingham model was applied to extract yield stress and plastic viscosity, which were subsequently used to estimate friction losses as a function of the Reynolds number. The predicted friction loss calculated using the Hedström number and the Bingham model showed excellent agreement with experimental data. Furthermore, the critical Reynolds number indicating the transition from laminar to turbulent flow was confirmed to increase with increasing yield stress. This trend is qualitatively consistent with flow stability predictions. Notably, the plastic viscosity obtained by this method was significantly lower than values estimated from sediment volume fractions using conventional viscosity correlations based on an effective volume fraction of flocs. These insights into the flow resistance of coagulated clay suspensions are useful for improving the design and operation of water purification, slurry transport, and solid–liquid separation processes.

Purification doi: 10.3390/purification2020006

Authors: Vasileios M. Pappas

Pulsed electric field (PEF) extraction studies often report yield gains but less consistently translate them into purification-relevant metrics. This study re-analyzed a locked comparability tier of 56 solvent-matched control (CTR)-PEF contrasts from five leaf-biomass studies to map total phenolic content (TPC) uplift onto first-order downstream duty proxies. The tier was not designed as a field-wide survey, and audit logs plus dependence-aware analyses were used to reduce author bias. Across the 56 pairs, median ΔTPC% was 26.7% (IQR 12.1–35.0), with positive values in 55 of 56 contrasts. The strongest gains were concentrated at low specific energy (Wspec ≤ 0.15 kJ kg−1 treated biomass) and 0–25% ethanol within this dataset. PLRI translated these uplifts into first-order processed-volume scaling at fixed capture criteria, and Pareto screening identified PLRI values of 1.18–1.73, corresponding to approximately 15–42% lower processed volume under the stated assumptions. Marker-level data were limited to two matrices (three paired observations), but SSF values > 1 (1.06–2.89) were consistent with possible composition steering. No new experiments were performed, and ballast, fouling, and downstream performance were not measured; conclusions are therefore limited to the operating envelope and are intended for screening, reporting standardization, and subsequent purification validation.

Purification doi: 10.3390/purification2020005

Authors: Stylianos Spathariotis Eirini Zagoraiou Anastasia-Maria Moschovi Ekaterini Polyzou Iakovos Yakoumis

Platinum group metals (PGMs), platinum (Pt), palladium (Pd) and rhodium (Rh), are critical for automotive emission control, chemical manufacturing and emerging energy technologies, yet their supply is limited and geographically concentrated. Their designation as critical raw materials (CRMs) in the EU has intensified recycling efforts, especially from spent automotive catalysts. Conventional pyrometallurgical and acid-based hydrometallurgical routes achieve high recovery efficiencies but rely on aggressive reagents and energy-intensive processing. Deep eutectic solvents (DESs) have emerged as greener leaching media capable of dissolving PGMs under milder and tunable conditions. This review outlines the conventional hydrometallurgical framework, summarizes DES fundamentals relevant to metals dissolution, and critically assesses recent advances in DES-based leaching of PGMs from spent catalysts. The influence of solvent composition, oxidants and complexing ligands on PGMs speciation and recovery is discussed, together with emerging reporting guidelines and research priorities. Overall, DES-based leaching offers a promising and potentially safer route for autocatalyst recycling but the technology remains at an early stage of development, requiring further mechanistic insight and sustainability evaluation.

Purification doi: 10.3390/purification2020004

Authors: Simona Serban Yanjun Li Gang Li Tongnian Gu Long Liu Xiaoju Lei Caroline Tinsley Xiaokang Kou Alessandra Basso

Native Staphylococcus aureus protein A exhibits strong affinity to the Fc and VH regions of human IgG1, IgG2, and IgG4, making it a valuable tool for monoclonal antibody (mAb) purification. However, its low stability under conditions such as increased alkaline concentrations during cleaning-in-place (CIP), protease exposure, thermal stress, and shear forces limits its usability for large-scale industrial applications. Recombinant Protein A (rProtein A) can be modified to improve key properties, including alkaline stability. In this study, we present targeted modifications to the C domain of native Protein A, evaluating multimeric variants for structural and functional improvements. The selected variant demonstrated extremely high stability after 60 h incubation at 0.5 M NaOH by maintaining more than >90% initial dynamic binding capacity (DBC) and up to 80% DBC after 40 h in 1.0 M NaOH. However, the most impressive result obtained was the stability of the ligand in 1.5 M NaOH, retaining 80% DBC after 22 h and 60% DBC after 40 h. To the best of our knowledge, this is the first time that such high alkaline stability is reported for a rProtein A. To assess its application in monoclonal antibody purification, the optimized rProtein A ligand was immobilized on agarose resin and tested in chromatography processes. The resulting chromatography resin functionalized with the CmZmb ligand (now commercialized by Sunresin, China under the name of rProtein A Seplife Suno) exhibited a high dynamic binding capacity of 70 mg/mL, minimal ligand leaching under operational conditions (~15 ppm), and extended lifecycle performance (88% DBC retained after 120 purification cycles with 0.5 M NaOH CIP), making it well-suited for industrial-scale applications.

Purification doi: 10.3390/purification2010003

Authors: Messan Justin Kessouagni Moursalou Koriko Koffi Fiaty Catherine Charcosset Gado Tchangbedji

Paracetamol (PAR) was selected as an emerging micropollutant model to evaluate the effectiveness of the photo-Fenton process using natural Bandjéli ore (BO) as a heterogeneous source of iron. An aliquot of 1 mL of the activated product was introduced into 200 mL of an aqueous solution of paracetamol at a defined concentration. The tests were conducted in a double-jacketed glass photoreactor (0.2 L), continuously stirred and equipped with two UVA PL-L lamps (36 W, λ = 365 nm), with the temperature maintained at 20 °C and the pH around 2.4. The photo-Fenton process was applied with different initial paracetamol concentrations (10–50 mg/L), different H2O2/PAR initial molar ratios (10:1 and 5:1), and different ferric ion concentrations (2.84–4.73 mg/L). Under these conditions, complete disappearance of the parent compound (paracetamol) was achieved in less than 3 h for iron contents below 5 mg/L, in compliance with the discharge standards applicable in France and Togo. Inhibition tests with propan-2-ol highlighted the predominant role of hydroxyl radicals and the secondary involvement of superoxide radicals in the subsequent stages. Taken together, these results demonstrate that Bandjéli iron ore is an effective, sustainable, and economically advantageous alternative to commercial iron salts for implementing the photo-Fenton process in the decontamination of water polluted by organic micropollutants.

Purification doi: 10.3390/purification2010002

Authors: Sagar Roy

The demand for global energy consumption, driven by population expansion and economic development, has intensified significantly over the decades and created substantial momentum for the development of sustainable energy technologies [...]

Purification doi: 10.3390/purification2010001

Authors: Bastian Greisner Magnus Rienäcker Frank Rögener André Lerch

Industrial whey dewatering via membrane processes remains challenging due to the rapid increase in viscosity, strong fouling tendencies from proteins and minerals, and the steep rise in osmotic pressure during concentration. These effects restrict operating windows and complicate energy-efficient process control. This study addresses the application of forward osmosis (FO) technology for industrial-scale dewatering of sweet whey using an Aquaporin Inside® HFFO14 module. Various feed- and draw-side cross flow velocities (0.0397 to 0.0524 m s−1 and 0.0127 to 0.0190 m s−1, respectively) and draw solution (DS) osmotic pressures of 20 bar and 60 bar were investigated using a production-scale prototype plant. Sweet whey had an initial osmotic pressure of 7 bar and an electrical conductivity of 5.7 mS cm−1. DS pressures of 20 bar and 60 bar resulted in a total recovery of 50% and over 80%, respectively. Water flux rates initially ranged from 10.1 to 11.6 L m−2 h−1 (LMH) and ceased at 3.3 LMH. Specific energy demand ranged from 0.15 to 1.1 kWh m−3. These findings support the feasibility of industrial-scale FO technology and underscore the potential of FO as an energy-efficient, sustainable solution for the dairy industry. However, frequent rinsing and cleaning routines are crucial to maintain membrane performance.

Purification doi: 10.3390/purification1030008

Authors: Yuying Wang Tianqi Wang Jin Shang

Despite significant progress in renewable energy development, nitrogen oxides (NOx) remain a persistent air pollutant [...]

Purification doi: 10.3390/purification1020007

Authors: Verena Hilgenfeldt Katrin Rübner Andreas Hahn Heidrun Steinmetz

Although various special materials have been studied for their potential for phosphorus removal in constructed wetlands, varying methodologies make direct comparisons of adsorption capacities observed in laboratory experiments difficult. This paper aims to establish a methodology for determining the optimal ratio of phosphate to material mass for different materials and for achieving the necessary contact time for adsorption isotherms. To minimise the number of experiments required, pretests over 24 h should be repeated to determine the phosphate-specific ratios until they show around 60% of the initial concentration. The tested materials included lava sand and expanded sand (ExS), which showed saturating kinetics curves after 24 to 48 h. However, aggregates containing calcium silicate hydrate (CSH) phases (autoclaved aerated concrete AAC, sand–lime brick SLB, and hydrothermal granules HTG) did not show saturating curves, complicating contact time determination. Consequently, adsorption velocity is proposed to identify the phase with the lowest adsorption rate, which is then used as the contact time in adsorption isotherm experiments. Using this method, adsorption times of 48 h were observed for HTG and SLB, while that for AAC was 24 h. This methodology is intended as an initial approach to establish a common basis for researchers investigating novel materials and make the results comparable.

Purification doi: 10.3390/purification1020006

Authors: Laiba Butt Anushree Das Alireza Tabibi Mousab Rehmani Benson Karimi

Heparin, an essential plasma-derived therapy, acts as a naturally occurring anticoagulant and is essential in various physiological processes. Due to its complex structure, repeating units of sulfated glycosaminoglycan, it attracts attention in the field of commercial pharmaceuticals. In recent decades, significant advancements have been made in the development of economical adsorbents designed especially for the extraction of heparin from the intestinal mucosa of pigs, as evidenced by investments from various pharmaceutical industries. This requirement arises from the demand for efficient, scalable extraction methods for natural sources. In this study, we investigated the application of beta zeolites to increase the recovery of heparin from real porcine mucosa samples, emphasizing materials with greater adsorption surfaces, higher thermal stability, and increased porosity. According to our research, the zeolite CP814E’s macropores and huge surface area allow it to adsorb up to 20.6 mg·g−1 (39%) of heparin from actual mucosa samples. We also investigated the adsorbent’s surface conditions, which are essential for efficient heparin recovery, and adjusted temperature and pH to enhance heparin uptake. These findings demonstrate that zeolite-based adsorbents can enhance the extraction of heparin effectively for use in medicinal applications.

Purification doi: 10.3390/purification1010005

Authors: Francesco Vegliò

Purification (ISSN 3042-6197) is an international, peer-reviewed, open access journal offering a platform for theories, emerging technologies, and practical applications of purification across chemistry, biology, chemical and environmental engineering, materials science, pharmaceutical technology, food engineering, and related areas [...]

Purification doi: 10.3390/purification1010004

Authors: Monika Gwadera Pawel Brzoskwinia Szymon Hnatyk Gabriela Kazberuk

In this study, the adsorption of a textile dye from water onto activated carbon is considered and the results of our own experimental studies on adsorption equilibrium and kinetics are presented. The adsorption isotherm and kinetic curves were found to reflect the possibility of removing the dye from water by adsorption onto activated carbon. Kinetic studies were conducted using a fixed bed of adsorbent grains. The water and dye solution flowed through the column with the adsorbent. The main aim of this study was to determine diffusion coefficients and mass transfer coefficients. The values of the external mass transfer coefficient and external diffusion coefficient of the dye in water were calculated for different flow rates of the solution, i.e., for different external resistance values. The external diffusion coefficient was DAB = 2.21·10−10 m2/s and the external mass transfer coefficient was between kc = 4.813·10−8 m/s for the lowest solution velocity in the adsorber equal to 0.0693 m/s and kc = 5.623·10−8 m/s for the highest velocity equal to 0.185 m/s. The internal diffusion coefficient and internal mass transfer coefficient, i.e., the coefficients of the transfer from the external surface of a grain to its interior, were determined with the use of the analytical solution of the diffusion and adsorption equation For the apparent solution velocity of 0.0693 m/s the internal diffusion coefficient was Ds = 0.57·10−10 m2/s and the internal mass transfer coefficient was ks = 1.89·10−10 m/s. For the velocity of 0.163 m/s, the internal diffusion coefficient was Ds = 0.84·10−10 m2/s and the internal mass transfer coefficient was ks = 9.00·10−10 m/s. The results of the calculations presented are a measure of the efficiency of a given adsorbent in a given system. The values obtained for the mass transfer coefficients can be used as data for further calculations of this process.

Purification doi: 10.3390/purification1010003

Authors: Ivan Notardonato Cristina Di Fiore Pasquale Avino

Indoor air quality (IAQ) has emerged as a critical area of research, reflecting growing concerns regarding occupant health, well-being, and comfort in enclosed environments. The increasing complexity of modern indoor spaces, coupled with rapid advancements in sensing technologies and data analysis methodologies, has intensified scientific interest in effective IAQ assessment and management. This review aims to examine current technologies and methodologies for monitoring key indoor air quality indicators. Furthermore, it offers practical recommendations for enhancing IAQ in diverse built environments and explores the integration of artificial intelligence (AI) into monitoring systems. The findings underscore the potential of AI-enhanced approaches to optimize indoor environmental conditions and support proactive air quality management strategies.

Purification doi: 10.3390/purification1010002

Authors: Lelum Duminda Manamperuma Janka Dibdiakova Ocelie Kjønnø Bjørn Rusten Josipa Matic Sileshi Gizachew Wubshet Eilen Arctander Vik

Crossflow membrane separation was used as a scalable downstream process for the up concentrate of low-molecular-weight peptides and for the removal of salt (NaCl) from Calanus finmarchicus hydrolysate. Membrane processes are increasingly used for various applications in both upstream and downstream processing. The C. finmarchicus hydrolysate was prepared by enzymatic hydrolysis, followed by crossflow separation. The stepwise membrane nanofiltration of hydrolysate contributed to a progressive reduction in salt in the hydrolysate. The salt concentration in the concentrates decreased by 34%, 53%, and 75%, highlighting the efficiency of the filtration process in separating NaCl from peptides. This gradual reduction in salt concentration suggests that the membrane effectively facilitated NaCl removal while retaining peptides. Briefly, 75% NaCl removal was achieved, with peptide recovery reaching 57% using an NFX membrane in crossflow filtration.

Purification doi: 10.3390/purification1010001

Authors: Karol Chilmon Maciej Kalinowski Wioletta Jackiewicz-Rek

This study investigates the relationship between surface properties and microstructural characteristics of photocatalytic composites and their impact on air purification efficiency. High-resolution energy-dispersive X-ray spectroscopy (EDS) mapping and mercury intrusion porosimetry (MIP) were employed to analyze photocatalyst distribution and pore structure quantitatively. The findings demonstrated a strong correlation between TiO2 coverage on the photoactive surface and NO removal rates and between pore structure characteristics and NO2 generation rates. Two predictive models were developed to link NOx removal rates with photocatalytic cementitious mortars’ surface and structural properties. A stepwise regression approach produced a second-degree polynomial model with an adjusted R2 of 0.98 and a Mean Absolute Percentage Error (MAPE) of 8.34%, indicating high predictive accuracy. The results underscore the critical role of uniform photocatalyst distribution and optimized pore structure in enhancing NOx removal efficiency while promoting the generation of desirable products (NO3−) and minimizing the formation of undesirable byproducts (NO2).