Search Results (76)

The dairy industry generates significant amounts of wastewater, including microfiltration (MF) retentate, a byproduct thickened with organic and inorganic pollutants. This study focuses on the treatment of two times concentrated MF retentate using a hybrid system based on biological treatment in a sequential batch reactor (SBR) and adsorption on activated carbon. The first stage involved cross-flow microfiltration using a 0.2 µm PVDF membrane at 0.5 bar, resulting in reductions of 99% in turbidity and 79% in chemical oxygen demand (COD), as well as a partial reduction in conductivity. The second stage involved 24-h biological treatment in a sequential batch reactor (SBR) with activated sludge (activated sludge index: 80 cm³/g, MLSS 2500 mg/dm³), resulting in further reductions in COD (62%) and TOC (30%), as well as the removal of 46% of total phosphorus (TP) and 35% of total nitrogen (TN). In the third stage, the decantate underwent adsorption in a column containing powdered activated carbon (PAC; 1 g; S_(BET) = 969 m² g⁻¹), reducing the concentrations of key indicators to the following levels: COD 84%, TOC 70%, TN 77%, TP 87% and suspended solids 97%. Total pollutant retention ranged from 24.6% to 97.0%. These results confirm that the MF–SBR–PAC system is an effective, compact solution that significantly reduces the load of organic and biogenic pollutants in MF retentates, paving the way for their reuse or safe discharge into the environment. Full article

In this study, a Bi₂O₃-TiO₂/PAC ternary composite photocatalyst was successfully synthesized via a hydrothermal method, employing powdered activated carbon (PAC) as the support and using bismuth nitrate and tetrabutyl titanate as raw materials. The external morphology, microstructure, elemental composition, and optoelectronic properties of the catalyst were characterized by XRD, SEM, TEM, XPS, UV-Vis DRS, and BET analyses. The photocatalytic activity of the composite toward the degradation of malachite green (MG) was systematically evaluated under various conditions. The results revealed that the composite exhibited excellent photocatalytic activity, achieving a degradation efficiency of up to 99%. Apart from extremely acidic or alkaline conditions, MG removal efficiency increased with a rising solution pH. Moreover, the photocatalyst exhibited excellent adaptability and stability in the presence of coexisting inorganic anions and humic substances, indicating its broad potential for practical applications. Reactive-species-trapping experiments indicated that superoxide radicals (·O₂⁻) were the primary active species in the degradation process, with hydroxyl radicals (·OH) and photogenerated holes (h⁺) acting synergistically. Moreover, the catalyst maintained over 90% removal efficiency after five consecutive cycles, demonstrating its excellent stability and reusability. This work provides a promising strategy and theoretical foundation for the efficient photocatalytic treatment of MG-contaminated wastewater. Full article

Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are emerging contaminants of concern as they persist in natural environments due to their unique chemical structures. This paper critically reviewed the adsorption of PFOA and PFOS, depending on their chemical structure, by different adsorbents as well as soil. Adsorption of PFOS generally surpasses that of PFOA across various adsorbents. Despite having the same number of carbons, PFOS exhibits greater hydrophobicity due to two major structural differences: firstly, it has one extra CF₂ unit and secondly, the sulfonate group in PFOS, being a relatively hard base, readily adsorbs on oxide surfaces, enhancing its adsorption compared to the carboxylate group in PFOA. While comparing activated carbon (AC) adsorption performance, powdered activated carbon (PAC) demonstrates higher adsorption capacity than granular activated carbon (GAC) for PFOS and PFOA. Anion exchange resin (AER) outperforms other adsorbents, with a maximum adsorption capacity for PFOS twice that of PFOA. Carbon nanotubes (CNTs) exhibit two-fold higher adsorption for PFOS compared to PFOA, with single-walled CNTs showing a distinct advantage. Overall, the removal of PFOS and PFOA under similar conditions on different adsorbents is observed to be in the following order: AER > single-walled CNTs > AC. Moreover, AER, single-walled CNTs, and AC exhibited higher adsorption capacities for PFOS than PFOA. In situ remediation studies of PFOA/S-contaminated soil using colloidal activated carbon show a reduction in concentration to below acceptable limits within 12–24 months. The theoretical and experimental studies cited in this review highlight the role of air–water interfacial adsorption in retaining PFOA and PFOS as a function of their charged head groups during their transport in unsaturated porous media. Full article

Low-cost powdered activated coke (PAC) produced by a one-step rapid method with lignite was used as an adsorbent for the advanced treatment of phenol-containing wastewater to evaluate the feasibility of replacing high-cost commercial powdered activated carbon. Characterization using infrared spectral analysis, SEM, and BET showed that the PAC mesopores were well developed. PAC exhibited a high adsorption performance for phenol in static experiments. The adsorption was almost in equilibrium within 20 min, and the removal efficiency reached 85.4% with 1.5 g L⁻¹ PAC and 99.9% with 4 g L⁻¹ PAC. As common components in wastewater, NaCl and Na₂SO₄ did not exhibit significant competitive adsorption with phenol in PAC. The adsorption process occurred in accordance with the Langmuir model and the pseudo-second order kinetic model. Furthermore, the effects of hydrothermal regeneration on PAC adsorbing phenol were studied, and the adsorption capacity of PAC after five regeneration cycles was 86.1% of that of the new PAC, which still had good adsorption performance. PAC offers significant advantages in terms of adsorption capacity, economic feasibility, regeneration, and recycling, providing a practical solution to the problem of phenol-containing wastewater pollution. Full article

The presence of dissolved sulfides in feed seawater causes severe elemental sulfur fouling in the reverse osmosis (RO) process. However, current pretreatment methods suffer from large footprint, high energy consumption, and limitations in effluent quality. In this study, adsorption and microfiltration are merged into a single process for the pretreatment of sulfide-containing seawater. Powdered activated carbon (PAC) was selected for its superior adsorption capacity (14.6-fold) and faster kinetics (3.9-fold) for sulfide removal compared to granular activated carbon. The high surface area and multiple pore structures of PAC facilitate surface and intraparticle diffusion, as well as anion–π conjugation likely occur between PAC and sulfide. Polypropylene microporous membranes, capable of tolerating high PAC dosages, were used in the hybrid process. Long-term pilot tests demonstrated that the effluent (turbidity < 1 NTU and SDI₁₅ ≈ 2.50) met the quality requirements for RO unit feedwater, achieving 100% sulfide removal efficiency over 101 h, with no risk of PAC leakage throughout the entire operation process. The formation of a loose, porous PAC cake layer alleviates membrane fouling and enhances the retention and adsorption of metal(loid)s and sulfide. Moreover, the low permeate flux of the polymeric membranes significantly mitigates filter cake formation. The hybrid system adapts to variations in feedwater quality, making it highly suitable for desalination plants with limited space and budget. These findings offer valuable insights and practical guidance for advancing seawater desalination pretreatment. Full article

The process of using powdered activated carbon (PAC) in conjunction with ultrafiltration (UF) has been widely adopted for the treatment of various types of water and wastewater. However, during the application of this integrated PAC-UF process, PAC tends to adhere significantly to the surface of the UF membrane, which exacerbates membrane fouling. To tackle this issue, this study proposed an innovative water treatment approach that simultaneously integrated granular activated carbon (GAC) and PAC/biochar with UF. In this setup, PAC/biochar was intended to enhance water quality, while the fluidized GAC particles were aimed at reducing membrane fouling and the deposition of PAC/biochar on the membrane surface. We systematically analyzed the operational performance of the integrated systems concerning fouling formation, PAC/biochar attachment, effluent quality, and foulant components. The results indicate that both PAC and biochar effectively improved effluent quality in terms of chemical oxygen demand (COD) and hardness, although they significantly deposited on the membrane surface during operation. Notably, PAC was more prone to attach to the membrane than biochar, and the fouling in biochar-UF systems was primarily attributed to the attachment of organic foulants rather than biochar itself. By combining with GAC, up to 46.01% of membrane fouling and 96.11% of PAC/biochar attachment were mitigated due to the strong mechanical action of the fluidized GAC particles. Importantly, the inclusion of fluidized GAC did not significantly affect effluent quality. Consequently, the GAC-PAC/biochar systems proposed in this study demonstrated dual benefits of improving effluent quality and ensuring stable operation, thereby providing a viable solution for efficient and sustainable water treatment. Full article

This experimental study explores the mitigation of membrane fouling in membrane bioreactors (MBRs) through the combined use of granular activated carbon (GAC) and powdered activated carbon (PAC). The research assesses the impact of these materials on the fouling resistance, critical flux, and permeate quality using various mixed liquor suspended solids concentrations and carbon dosages. The results indicate that the GAC-PAC combination significantly reduces the total filtration resistance, particularly the cake layer resistance, by 11.7% to 13.6% compared to setups without activated carbon or with the individual carbon types. The study also reveals that this combination decreased the fouling rate by 15% to 24% at critical flux steps, demonstrating substantial improvements in fouling mitigation and operational efficiency. Furthermore, the GAC-PAC combination, which produces an adsorption process, enhances the permeate quality, achieving the near-complete removal of organic matter, total nitrogen, and turbidity, with total phosphorus removal reaching 99%. These findings demonstrate that the combined use of GAC and PAC not only reduces membrane fouling but also improves the overall MBR performance, making it a viable strategy for enhancing the efficiency of wastewater treatment processes. Full article

Organic micropollutants (OMPs) present in water and wastewater are in the spotlight because of their potentially harmful effects even at low concentrations and the difficulties of their elimination in urban wastewater treatment plants (UWWTPs). This study explores the impact of some membrane filtration processes on the removal of a group of 11 OMPs with an eye on the effects of two pretreatments (i.e., coagulation and adsorption onto powdered activated carbon (PAC)) and the adsorption of OMPs onto the membranes on the overall removal. For this purpose, ultrafiltration (UF) and nanofiltration (NF) experiments were conducted with selected OMPs spiked in ultrapure water and secondary effluents from UWWTPs. It was observed that the adsorption of OMPs onto the membranes was influenced by the characteristics of the membranes, as well as the presence of effluent organic matter (EfOM). Since adsorption was the dominant mechanism for the rejection of OMPs by UF membranes, a study of the adsorption equilibrium of the micropollutants using UF membrane pieces as the adsorbent was conducted. The adsorption isotherms for the most hydrophobic OMPs fitted the Langmuir model. The efficiency of coagulation and powdered activated carbon (PAC) adsorption coupled with UF were also investigated. Both pretreatments alleviated membrane fouling and improved the rejection of organic and inorganic matter. The PAC pretreatment significantly improved the removal of OMPs in the combined PAC/UF process. The best options for achieving reclaimed water with satisfactory physicochemical quality, nearly devoid of OMPs and microorganisms, and suitable for diverse reuse purposes are either the NF treatment or the combination of PAC/UF. Full article

This paper presents research on the mass dispersion and adsorption of organics present in tap water on powdered activated carbon (PAC) in a two-layer filter column. The adsorption rate depends on the difference between the concentration of organics and the equilibrium concentration. In homogeneous flocculators with simultaneous adsorption on PAC, the concentration difference is lower than in a filter column with PAC. Therefore, the utilization of the PAC’s adsorption capacity in filters is higher than in homogeneous flocculators. PAC is introduced into the upper anthracite layer of a filter bed, while the bottom layer is a sand layer, which protects the underdrain system from becoming clogged with PAC particles. The sorbent wis introduced into the bed in the final phase of filter backwashing. The authors present a model of adsorption on PAC in a filter column. Both experiments and calculations confirmed a better utilization of PAC’s adsorption capacity in the filter column compared to its utilization in a homogeneous flocculator. Three criterion equations were developed using dimensionless numbers, Re, Pe and Nu, as well as two similarity moduli related to a sorbent apparent density and an adsorption coefficient. Additionally, a relationship between the Peclet number (Pe) and the Reynolds number (Re) as well as the similarity modulus for the sorbent apparent density were determined for the mass dispersion process. The relationship between the diffusive Nuselt number (Nu) and the Re number as well as the similarity modulus for the sorbent apparent density were determined for the parameter describing an adsorbate permeation rate across a water–sorbent interface. The impact of the Re number and the similarity modulus for the sorbent apparent density on the Henry constant was also investigated. The criterion equations can be used to determine the adsorption model parameters; they may be helpful in designing a filtration system supplemented with PAC. In the capillary velocity range $V_x^{*}$ ∈ ⟨0.15·10⁻²; 0.72·10⁻²⟩ m/s and with a change in the apparent density of the sorbent ${\rho }_{p,sorb}$ from 3000 to 12,000 g PAC/m³ of the bed, as a result of the experimental tests carried out, it was established that the actual coefficient of longitudinal dispersion $D_x^{*}$ varied in the range of 0.16·10⁻⁴ to 2.03·10⁻⁴ m²/s, the product of the constant mass transfer rate and the specific outer surface of sorbent $k\cdot a_m$ varied in the range of 2.23·10⁻⁷ to 1.70·10⁻⁶ (m/s)·(m²/g PAC), while the Henry constant Γ* varied in the range of 7.24 to 44.20 1/m³ of sorbent and the Henry constant Γ varied in the range of 0.0012 to 0.0019 m³ of water/g PAC. Full article

Today’s environmental issues related to wastewater are being tackled by growing public concern and tighter international regulation. Pollutant removal from wastewater is still a very challenging task. The removal of heavy metals from industrial and agricultural wastewater is a complex environmental issue due to its potential health hazards. There are different methods used for wastewater treatment. However, these technologies are either frequently ineffective or generate secondary metabolites. Adsorption, a physicochemical method, has proven effective in eliminating low-concentration inorganic pollutants. Powdered activated carbon and natural powders have emerged as potential solutions in urban wastewater treatment. This study provides an overview of their applications and effectiveness in removing contaminants from wastewater, thereby improving the overall treatment efficiency and water quality. For this purpose, experiments have been performed using three types of powders: Saccharum officinarum powder and its powdered activated carbon as an adsorbent, and Luffa aegyptiaca Luffa aegyptiaca powder. This study focused on the adsorption treatment of natural powders influenced by different parameters (pH, infrared spectroscopy, contact time, concentration, mass and particle size) during laboratory experiments. By maintaining a few parameters and using natural powders without carbonization or prior activation, this study demonstrated that powdered activated carbon remains more effective and shows better results than natural powders. Full article

The necessity to eliminate nickel (Ni) from wastewater stems from its environmental and health hazards. To enhance the Ni adsorption capacity, this research applied a copper sulfate–ammonia complex (tetraamminecopper (II) sulfate monohydrate, [Cu(NH₃)₄]SO₄·H₂O) as a modifying agent for a Phragmites australis-based activated carbon preparation. The physiochemical properties of powdered activated carbon (PAC) and a modified form ([Cu(NH₃)₄]-PAC) were examined by measuring their surface areas, analyzing their elemental composition, and using Boehm’s titration method. Batch experiments were conducted to investigate the impact of various factors, such as Ni(II) concentration, contact time, pH, and ionic strength, on its substance adsorption capabilities. Additionally, the adsorption mechanisms of Ni(II) onto activated carbon were elucidated via Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The findings indicated that modified activated carbon ([Cu(NH₃)₄]-PAC) exhibited a lower surface area and total volume than the original activated carbon (PAC). The modification of PAC enhanced its surface’s relative oxygen and nitrogen content, indicating the incorporation of functional groups containing these elements. Furthermore, the modified activated carbon, [Cu(NH₃)₄]-PAC, exhibited superior adsorption capacity relative to unmodified PAC. Both adsorbents’ adsorption behaviors conformed to the Langmuir model and the pseudo-second-order kinetics model. The Ni(II) removal efficiency of PAC and [Cu(NH₃)₄]-PAC diminished progressively with rising ionic strength. Modified activated carbon [Cu(NH₃)₄]-PAC demonstrated notable pH buffering and adaptability. The adsorption mechanism for Ni(II) on activated carbon involves surface complexation, cation exchange, and electrostatic interaction. This research presents a cost-efficient preparation technique for preparing activated carbon with enhanced Ni(II) removal capabilities from wastewater and elucidates its underlying adsorption mechanisms. Full article

In this research, a new catalyst for activating persulfate was developed by loading iron and nickel ions onto powdered activated carbon (PAC) for treating methyl orange, and the preparation process was optimized and characterized. The efficacy of the treatment was evaluated using the Chemical Oxygen Demand (COD) removal rate, which reflects the impact of various process parameters, including catalyst dosage, sodium persulfate dosage, and reaction pH. Finally, the recovery and reuse performance of the catalyst were studied. The optimal conditions for preparing the activated sodium persulfate catalyst were determined to be as follows: a molar ratio of Fe³⁺ and Fe²⁺ to Ni of 4:1, a mass ratio of Fe₃O₄ to PAC of 1:4, a calcination temperature of 700 °C, and a calcination time of 4 h. This preparation led to an increase in surface porosity and the formation of a hollow structure within the catalyst. The active material on the surface was identified as nickel ferrite, comprising the elements C, O, Fe, and Ni. The magnetic property is beneficial to recycling. With the increase in catalyst and sodium persulfate dosage, the COD removal efficiency of the oxidation system increased first, and then, decreased. The catalyst showed good catalytic performance when the pH value was in the range of 3~11. Furthermore, Gas Chromatography–Mass Spectrometry (GC-MS) analysis indicated the complete oxidation of methyl orange dye molecules in the system. This result highlights the important role of the newly developed catalyst in activating persulfate. Full article

In this study, the facile removal of the chromium-complex-based reactive azo dye C. I. Reactive Black 8 (RB8) from model wastewaters by the co-action of alternative sorbents—biochar (BC) and bentonite (BT)—with ionic liquids such as benzalkonium chloride (BAC) or Aliquat 336 (A336) was studied. The experiments using model RB8-containing wastewater proved that the co-action of BAC with BC is the most promising method of RB8 separation from wastewater containing 1 g L⁻¹ of RB8 dye. The application of 2 g L⁻¹ BC in co-action with 1.5 g L⁻¹ BAC or 1 g L⁻¹ BT in co-action with 2 g L⁻¹ BAC enables the removal of more than 98% of contaminant RB8 after 30 min of action. Similar removal efficiency (RE) was achieved using 40 g L⁻¹ of powdered activated carbon (PAC) after 180 min of action. To reach the same RE using real RB8-containing wastewater, a four times higher dose of BC and a four times higher dose of BAC per gram of removed RB8 were required. The proposed mechanism of RB8 removal by the co-action of alternative sorbents with BAC comprises a parallel effect of (i) sorption, (ii) the formation of less polar ion pairs accompanied by their sorption on an alternative sorbent and (iii) the separation of used alternative sorbents covered with ion pairs. The removal efficiency of organic contaminant(s) from both model and real wastewater was evaluated by VIS spectroscopy applying the Lambert–Beer law and by the determination of chemical oxidation demand (COD) and/or adsorbable organically bound halogen (AOX) parameters. Full article

Membrane fouling is a key factor limiting the application of a membrane bioreactor (MBR), and membrane-surface modification holds the potential to control membrane fouling and solves this problem. In the research, novel nanocomposite membranes were designed and fabricated using antimicrobial copper nanoparticles (CuNPs) coupled with powdered active carbon (PAC) to mitigate membrane fouling. The successful coating was confirmed by SEM, XRD, and FTIR analysis. Compared with a pristine membrane, the functionalization of CuNPs and PAC improved the hydrophilicity of the modified membrane but led to a lower permeate flux. The result of antimicrobial adhesion experiments showed that the modified M-CuO_C displayed high antibacterial activity with the bacteria count decreased by 72%. In MBR operation, the modified M-CuO_C leads to the removal efficiency of chemical oxygen demand (COD) increasing to 93%, with better filtration performance under a lower TMP rise. The fouling-resistance analysis demonstrated that, although the intrinsic membrane resistance of modified M-CuO_C slightly increased, the reversible and irreversible fouling resistances obviously decreased by 45% and 90%. Moreover, the membrane flux recovery efficiency of the modified M-CuO_C also increased by 35%. Overall, these results indicated that, in addition to an improvement in antifouling performance, the functionalization of CuNPs and PAC also enhanced the membrane flux recovery efficiency, revealing a good antifouling potential in a practical application. Full article

Per- and polyfluoroalkyl substances (PFAS) are anthropogenic compounds developed for various applications; some are connected to adverse health impacts including immunosuppression and higher susceptibility to some cancers. Current PFAS remediation treatments from aqueous sources include granular activated carbon (GAC) adsorption, membrane separation, and anion-exchange resin (AER) removal. Each has specific disadvantages, hence the need for a new and efficient technology. Herein, acrylamide-based hydrogel composites were synthesized with powdered activated carbon (PAC) and characterized to determine their affinity for PFAS. Physicochemical characterization included Fourier-Transform infrared spectroscopy (FTIR) to identify chemical composition, thermogravimetric analysis (TGA) to confirm PAC loading percentage, and aqueous swelling studies to measure the effect of crosslinking density. FTIR showed successful conversion of carbonyl and amine groups, and TGA analysis confirmed the presence of PAC within the network. Surface characterization also confirmed carbon-rich areas within composite networks, and the swelling ratio decreased with increasing crosslinking density. Finally, sorption of PFAS was detected via liquid chromatography with tandem mass spectrometry (LC-MS/MS), with removal efficiencies of up to 98% for perfluorooctanoic sulfonic acid (PFOS) and 96% for perfluorooctanoic acid (PFOA). The developed hydrogel composites exhibited great potential as advanced materials with tunable levers that can increase affinity towards specific compounds in water. Full article