High Removal Efficiency Research Articles

In-depth analysis of natural organic matter fractions in drinking water treatment performance: Fate and role of humic substances in trihalomethanes formation potential

In this study we investigate the compositional changes in dissolved organic matter (DOM) fractions across diverse water sources and treatment processes in three Drinking Water Treatment Plants (DWTPs). High-Performance Size Exclusion Chromatography coupled with Diode Array Detection and Organic Carbon Detection (HPSEC-DAD-OCD) was employed to characterize DOM fractions, offering insights into treatment optimization. We examine bulk water parameters, DOM distributions, and the efficiency of treatment trains in reducing DOM fractions. Results reveal distinct DOM composition profiles in river-sourced versus reservoir-sourced waters, with implications for treatment processes. Coagulation, Granular Activated Carbon (GAC) adsorption, Electrodialysis Reversal (EDR), and Ion Exchange (IEX) were evaluated for their efficacy in removing DOM fractions. The analysis highlights the effectiveness of coagulation in reducing high molecular weight (MW) fractions, while GAC filtration targets lower MW fractions. EDR shows significant removal of anions and aromatics, while IEX demonstrates high removal efficiencies for removing humic substances (HS) fractions. Spectroscopic analysis further elucidates changes HS sub-fractions and their role in disinfection by-products (DBP) formation. To quantitatively assess the relationship between HS sub-fractions and trihalomethane formation potentials (THMFP), Pearson correlation analysis were conducted, unveiling robust associations between HS sub-fractions and THM-FP that can be predicted by surrogate parameters such as A254.

Effective removal of fluoride ions from contaminated water using electrochemical techniques: A critical review on recent developments and environmental perspective

Worldwide, water pollution poses significant threats to human health, with fluoride contamination emerging as a critical hazard. High fluoride concentrations in water cause severe health impacts, including dental and skeletal fluorosis, neurological damage, and harm to the parathyroid gland, cardiovascular, and reproductive systems. Electrochemical technique is one of the most widely used treatment technologies that has been extensively studied and provides a very effective, low-cost method of removing fluoride from contaminated water. The review reports the comprehensive electrochemical strategies for fluoride ions removal. The sources, toxicity, and impacts of fluoride pollution on health are discussed in this review. A comprehensive analysis of current electrochemical methods, including electrolysis, electrocoagulation, and the electro-fenton process, was provided in the context to facilitate the efficient removal of fluoride ions from wastewater. These methods exhibit high removal efficiencies, reaching up to 95 %, and offer scalability and operational flexibility, making them suitable for both centralized and decentralized water treatment systems. Furthermore, the recent advancements in the development of electrochemical technique for fluoride removal are critically reviewed. This study has prospected the recent developments, recommendations and future outlooks on electrochemical technique for fluoride removal.

Numerical and experimental investigation of floating wick solar still with a porous-media system

Wick-based solar desalination and solar-driven interfacial evaporation have attracted significant attention for their high efficiency in evaporation and salt removal. This study presents both experimental and numerical models for wick solar desalination. Cotton fabric, coated with black carbon for enhanced radiation absorption, was used as the evaporation medium in experiments due to its superior desalination, capillary, and salt rejection properties. Experimental results showed an evaporation rate of 1.57 kg/m2·h and efficiency of 81 % with freshwater. For saltwater (3.6 % salinity), the evaporation rate and efficiency were 1.24 kg/m2·h and 71 %, under 1000 W/m2 radiation. After validating the numerical model, the effects of porosity, capillary pressure, wick thickness, and thickness of the fabric’s upper (solar absorber) layer were examined. Results showed that reducing the solar absorber fabric thickness (from 9 mm to 0.6 mm), lowering porosity (from 0.97 to 0.3), and increasing wick thickness (from 1.5 mm to 10.5 mm) improved evaporation rates by 58.6 %, 27 %, and 28.4 %, respectively. Capillary pressure and fabric submerged length had minimal effects on evaporation. The model estimates that in real conditions at Jask coastal port (Iran), a configuration with greater wick thickness (6 mm vs. 3 mm), reduced solar absorber fabric thickness (1 mm vs. 1.5 mm), and lower porosity (0.75 vs. 0.93) could increase annual freshwater output by 26.6 % (from 796.6 to 1008.4 kg/m2). The cost per liter of produced water in the best-case scenario is estimated to be $0.0045.

Wastewater treatment optimization utilizing polyvinyl alcohol cryogel immobilized microalgae for nutrient removal

This study investigated the use of polyvinyl alcohol (PVA) cryogels to immobilize microalgae for wastewater treatment. Chlorella sorokiniana was successfully entrapped in PVA cryogels via repeated freeze/thaw cycles. The nutrient removal efficiency of these cryogels was tested in a continuously stirred photobioreactor under varying conditions, both with and without the addition of an organic carbon source (sodium acetate). The presence of organic carbon significantly enhanced nutrient removal. Specifically, PVA cryogels with immobilized C. sorokiniana achieved 100% nitrogen removal and 97.2% phosphorus removal under mixotrophic conditions. Furthermore, the maximum nutrient removal capacities of the PVA cryogels were found to be 0.033 mg-N/cube·day for nitrogen and 0.0047 mg-P/cube·day for phosphorus. As the inorganic carbon (bicarbonate) concentration increased from 5 to 100 mg/L, the N/P ratio rose from 6 to 8, with a higher N/P ratio of 10 observed when nitrate nitrogen was used as the nitrogen source, compared to ammonia nitrogen, at 100 mg/L bicarbonate. This study offers an effective method for using microalgae immobilized in PVA cryogels for wastewater treatment. The findings highlight the potential for PVA cryogels to significantly improve nutrient removal efficiency, particularly in the presence of organic carbon sources, thereby enhancing bioreactor performance. High nitrogen and phosphorus removal efficiencies can help reduce eutrophication in water bodies, protect aquatic ecosystems, and enable nutrient recovery and reuse, supporting a circular economy in wastewater treatment practices.

Wastewater treatment using black soldier fly larvae: Influence of larval density and solid support

The use of Black Soldier Fly larvae for wastewater treatment has emerged as a promising alternative, coupling high removal efficiency with recovery of high-value products. To overcome the critical issue of larvae mortality in a liquid environment, a patented solution employs a physical porous support to be saturated by liquid, allowing larvae mobility. In view of process optimisation, a knowledge gap persists regarding both the optimal supporting material and larval density. The optimum supporting material and larval density should maximise the porosity (i.e. active volume of the reactor) and the removal efficiencies respectively, without compromising the survival rate. In the present study, three different plastic products (granules, pall rings and geomat) were tested at four different larval densities (4, 8, 16 and 32 larvae/cm2). Process performance was compared in terms of larval growth and substrate removal. An increase in larval density only impairs process once threshold density is exceeded. The threshold depended on the supporting material: higher porosity materials allow the use of higher larval densities, and therefore higher organic loads, with reduced reactor volumes.The best performance was achieved at larval density of 16 larvae/cm2 with pall rings, resulting in a survival rate and carbon removal efficiency of approx. 92 % and 97 % respectively.

Effect of different set of electrodes for degradation of distillery spent wash promoted by electrocoagulation

ABSTRACT One of the most polluting industries in the world is the distillery industry, which produces strong distillery wastewater that has an adverse impact on the environment since it contains high organic matter. Using various combinations of electrodes in the electrocoagulation process, to examined the operational variables, viz., total dissolved solids (TDS), electrical conductivity (EC) and turbidity from the distillery spent wash. With a constant pH of 7, an agitation speed of 500 RPM, and optimizing the operating parameters, viz., varying the electrode distance (2, 3, 4, 5, and 6 cm), voltage (5–25 volts) current density of 1.5 A/cm2, and electrolysis time (30–150 min). Aluminium (Al) electrodes were observed to perform slightly better than iron (Fe) and zinc (Zn) electrodes, with punched Al electrodes outperforming plane Al electrodes. The highest removal efficiencies were achieved with punched Al electrodes in an optimized condition of voltage 25 volts, electrode distance (2 cm), and electrolysis time 150 minutes, with removal efficiencies of 91% for TDS, 92% for EC and 92% for turbidity. This study highlights the potential of electrocoagulation with optimized parameters for improving the purification of distillery spent wash and enhancing the removal of TDS, EC, and turbidity.

Composite biopolymer foams fabricated from natural aldehyde functionalized chitosan-whey protein amyloid fibrils: Application for removal of phthalate esters from water

In this work, composite biopolymer foams from chitosan and whey isolate protein amyloid fibrils were prepared for the removal of phthalate esters from water. Natural aldehyde functionalization enhanced the affinity for dibutyl phthalate (DBP), with citral being the most effective. The citral-grafted foams (WCGC) had tunable hydrophobicity, strong mechanical properties, and good water stability. WCGC1.5 foam exhibited a high removal efficiency (96.06 %) of DBP. The adsorption process reached adsorption equilibrium rapidly within 8 h and could be described by pseudo-second-order kinetic and Freundlich isotherm models, indicating a non-homogeneous and chemisorptive sorption process. The maximum adsorption capacity for DBP reached 332.42 mg/g. Moreover, DBP adsorption could be enhanced in alkaline environment and the removal efficiency increased to 98.27 % at pH 10. The removal efficiency of DBP by WCGC1.5 remained above 85 % after the five adsorption-desorption cycles. WCGC1.5 also showed broad-spectrum adsorption behavior, with strong affinity and removal efficiency for six common plasticizers, including DIBP (85.97 %), DPP (91.7 %), DHXP (99.1 %), DEHP (99.09 %), DNOP (91.6 %) and BBP (89.88 %).

Electron transfer mechanism mediated MOF-derived nanoflowers catalyst for promoting peroxymonosulfate activation and ciprofloxacin degradation

Three MOF-derived nanoparticles were synthesized by manganese doping and calcination of ZIF-67 precursor. The surface physicochemical properties of these materials were compared using SEM, TEM, XRD, FTIR and BET analyses. Among them, cobalt-manganese oxide nanoflowers (CoMn2O4-NFs) exhibited excellent catalytic performance in the degradation of ciprofloxacin (CIP) by activated peroxymonosulfate (PMS), achieving 100 % removal within 30 minutes with a rate constant (kobs) of 0.2960 min−1. The catalytic mechanism was elucidated by quenching experiments, EPR, electrochemical analysis and X-ray photoelectron spectroscopy (XPS). The results show that the non-radical oxidation process was initiated mainly by direct electron transfer and 1O2 (∼80 %), with a small contribution from the radical SO4·- (∼20 %). The nano-confined structure on the surface of CoMn2O4-NFs makes it easy to combine with PMS to form CoMn2O4-NFs/PMS* complexes, which directly capture electrons from CIP to complete the degradation process. The double redox cycle of cobalt-manganese ions and oxygen vacancies on CoMn2O4-NFs could accelerate the electron transfer process. CoMn2O4-NFs maintained high removal efficiency (>99 %) over a wide pH range (3−11), with minimal interference from most environmental anions, demonstrating strong stability and interference resistance. This study provides insights into using metal-based materials for oxidative degradation of organic pollutants via non-radical pathways.

Uniformly dispersed FeOOH nanoparticles supported on alumina-carbon nanosheets for Cr(VI) removal

The mesoporous alumina-carbon nanosheets supported FeOOH nanoparticles were prepared by a facile and cost-effective hydrothermal synthesis for Cr(VI) removal in the wastewater, based on the affinity and selectivity of FeOOH and the accelerated mass transfer of nanosheet structure. The prepared nanoparticles with a small size of 2–5 nm were uniformly dispersed over the alumina-carbon nanosheets, attributed to the metal interaction and mesoporous confinement. The acid property after the introduction of alumina induced a positive charge on the surface of the adsorbent, which could enhance the adsorption of negatively charged metal ions. The Cr(VI) removal efficiency with the Al/Fe ratios showed a similar volcano curve. When Al/Fe ratio was around 3.3 and pHpzc was about 7.1, the adsorbent exhibited the best Cr(VI) removal efficiency of 99.4 %, owing to a large specific surface area, and small nanoparticle size, combined with abundant moderate-strong acid content of 294.5 μmol NH3 g−1.The Langmuir model could describe the adsorption process well, and the kinetic data was consistent with Pseudo-second-order. The thermodynamics revealed that the reaction process was spontaneous and endothermic. The adsorbent maintained a high removal efficiency of more than 80 % after running for five cycles and kept over 95 % under ionic co-existence and natural water conditions. Therefore, this study provides a new insight into the rational construction of efficient adsorbents with low-cost Cr(VI) removal.

Metal adsorption equilibrium response of iron oxide nanoparticles embedded on Acacia (Vachellia nilotica) wood waste under different parametric conditions

The present study reveals cost-effective, environmentally approachable, and efficient adsorbent for the elimination of heavy metals by utilizing the biological synthesis route of nanoparticles (NPs). IONPs (hematite) synthesized from Vachellia nilotica wood waste. Raw wood waste and IONPs were characterized by SEM and FTIR. A batch adsorption process was conducted to study the adsorption of lead (Pb+2) and (Cu+2) ions by raw wood waste and IONPs synthesized from wood waste. Parameters like pH change, temperature, dosage of sorbent, and contact time were performed to provide information about optimal conditions for adsorption. It was found that an adsorbent dosage of 4 g, pH = 7, temperature = 120 °C, and time of 20 min provided high removal efficiency of both metals. With Langmuir and Freundlich adsorption isotherm, experimental data matched well with a high adsorption capacity of 7.5 mg/L for Cu (II) and 0.83 mg/L for Pb (II). Kinetics study shows that equilibrium data supports with pseudo-second-order model with the highest R 2=0.99. Thermodynamics study (ΔGo, ΔHo, and ΔSo) shows that the process is feasible and has an endothermic nature. IONPs provide high removal efficiency with R 2=0.99 with both metals. IONPs proved as efficient adsorbents with high removal efficacy of studied metal as paralleled to raw wood waste.

Trace iron induced piezo-polarization field strength on piezo-promoted peroxymonosulfate activation for pollutant degradation

Advanced oxidation processes based on piezo-promoted peroxymonosulfate (PMS) activation in environmental remediation have been widely applied, but the treatment efficiency of pollutants was restricted by sluggish charge separation and low affinity of PMS. Herein, trace iron-doped layered molybdenum disulfide (Fe/MoS2) was used to degrade pollutants by piezo-promoted PMS activation. Real-time reaction site changes in carbamazepine (CBZ) degradation process were predicted by Fukui function calculation of the reaction intermediates, and the possible degradation pathways were given. Through piezoresponse force microscopy and calculation of the adsorption energy, electronic localized functions and Crystal Orbital Hamilton Population, it was verified that Fe doping improves the adsorption of oxygen-containing reactants on MoS2, enhancing the electron delocalization and piezo-polarization field, thus accelerating the piezo-promoted PMS activation kinetics. The degradation efficiency of CBZ on Fe/MoS2 (0.44 min−1) was about 22 times than that of MoS2. Piezo-promoted PMS activation strategy based on Fe/MoS2 still maintains a high removal rate in the treatment of dye and antibiotic pollutants such as ornidazole, rhodamine B, tetracycline, methyl orange, chlortetracycline. This study provides insights into the mechanism by which piezo-promoted PMS activation, and achieving high chemical efficiency for pollutants removal.

Efficiency of Canna indica, Phragmites australis and Eichhornia crassipes in Remediation of Leachate Through a Vertical Flow Constructed Wetland

Leachate treatment and disposal from landfills is one of major environment concern. Leachate contains various pollutants which may cause various environmental and health problem to terrestrial and aquatic living bodies. In the Present study, Landfill leachate was collected from Okhla landfill, New Delhi and treatment of leachate was done by using laboratory scale vertical flow treatment grown with Canna indica, Phragmites australis and Eichhornia crassipes, respectively. The experimental plots were obtained by set up of four different flow rates by balancing the inflow manipulations to obtain detention times of 1,7,14 for 21 days. The reduction of COD, BOD, NH4-N, TSS and heavy metals (Cd, Cu, Co, Cr, As, Pb, Ni, Fe, Zn and V) were investigated for 21 days. Average removal efficiency (%) for VCW (W1) planted with Canna indica showed 77.7%, 78.7%, 63.6%, and 76.7% for COD, BOD, NH4-N and TSS, respectively. Heavy metal removal (%) efficiencies of W1 planted with Canna indica was 60%, 82.5%, 100%, 29.37%, 27.9%, 62.67%, 13.33%, 44.5%, 75.2% and 78.85% for As, Cr, Cd, Cu, Co, Fe, Mn, Pb, Zn and V, in given order. VCW(W2) planted with Eicchornia crassipes species has shown reduction efficiency (%) of COD (68.5%), BOD (52%), NH4-N (45.4%), TSS (92.75%), respectively and in case of heavy metal 89.9% Cr, 100% Cd, 53.49% Cu, 62.7% Co, 85.2% Fe, 67.9% Ni, 76.2% Pb, 83.08% Zn, 65% As and 61.15% V, respectively. VCW (W3) planted with Phragmites australis exhibited removal efficiency (%) of COD (68.5%), BOD (52%), NH4-N (45.4%) and TSS (92.7%), respectively. Phragmites australis was able to remove As (100%), Cd (100%), Cr (89.9%), Cu (53.49%), Co (62.7%), Fe (85.82%), Ni (67.9%), Pb (76.2%), V (61.15%) and Zn (83.08%), respectively. All the three species were able to remove Cd (100 %). However, Canna indica (W1) has highest removal efficiencies (%) of COD (77.7%), BOD (78.7%) and NH4-N (63.6 %), respectively. Eicchornia crassipes has highest reduction efficiency (%) of TSS (92.75%), Cr (89.9%), Cd (100%), Cu (53.49%), Co (62.7%), Fe (85.2%), Ni (67.9%), Pb (76.2%) and Zn (83.08%), respectively. Phragmites australis was found good for removal of As (100 %) and Cd (100%). The result highlighted that these plant species can be used as single in lab scale Constructed wetland for the treatment Organic pollutants and heavy metals from landfill leachate.

Efficiency of water hyacinth and cattail for wastewater treatment using constructed wetland

Constructed wetlands have emerged as a cost-effective, eco- friendly and sustainable solution to enhance water quality by effectively removing nutrients. The objective of this study is to compare water hyacinth (Eichhornia crassipes) and Cattail (Typha latifolia) as wetland plants for wastewater treatment at the National Water Resources Institute (NWRI) situated in Kaduna State, Nigeria. The percentage removal of various parameters including pH, Total Dissolved Solids (TDS), Turbidity, Total Suspended Solids (TSS), Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Phosphorus, Nitrate, Ammonia, Sulphate, Oil and Grease, Total Coliform, Feacal Coliform, Copper, Zinc, Iron and Lead were compared for cattail and water hyacinth. The results of the analyzed parameters were compared with the Food and Agricultural Organization of United Nations (FAO, 2015) limits for irrigation purposes. Results showed pH, TDS, Turbidity, TSS, Sulphate, Nitrate, BOD, COD, FC, and Iron, Copper, Lead and Zinc were within permissible limit of the standard for irrigation water quality according to FAO, while EC and Total Phosphorous were above the maximum permissible limit. The result of the percentage removal efficiency showed that water hyacinth had higher performance in removing the pH (13.34%), Turbidity (97.24%), Sulphate (100%), Nitrate (18.51%), Total Phosphorous (96.34%), COD (86.21%), BOD (77.92%), Oil and Grease (73.80%), FC (78.48%), TC (36.24%), Copper (81.84%), Lead (89.69%) and Zinc (79.38%) compared to typha latifolia. For 82.61% EC, 82.09% TDS, 94.51% TSS, 97.31% Iron and removal, efficiency of typha latifolia was higher. Constructed Wetland vegetated with typha latifolia and Eichhornia crassipes showed high contaminant removal efficiency with water hyacinth showing superior removal efficiency

Enhancing Wastewater Treatment with Aerobic Granular Sludge: Impacts of Tetracycline Pressure on Microbial Dynamics and Structural Stability.

This study evaluated the efficiency of aerobic granular sludge (AGS) technology in treating wastewater contaminated with tetracycline (TC), a common antibiotic. AGS was cultivated under a TC pressure gradient ranging from 5 mg/L to 15 mg/L and compared with conventional wastewater conditions. The results demonstrated that AGS achieved high removal efficiencies and exhibited robust sedimentation performance, with significant differences in average particle sizes observed under both conditions (618.6 μm in TC conditions vs. 456.4 μm in conventional conditions). Importantly, exposure to TC was found to alter the composition and production of extracellular polymeric substances (EPSs), thereby enhancing the structural integrity and functional stability of the AGS. Additionally, the selective pressure of TC induced shifts in the microbial community composition; Rhodanobacter played a crucial role in EPS production and biological aggregation, enhancing the structural integrity and metabolic stability of AGS, while Candida tropicalis demonstrated remarkable resilience and efficiency in nutrient removal under stressful environmental conditions. These findings underscore the potential of AGS technology as a promising solution for advancing wastewater treatment methods, thus contributing to environmental protection and sustainability amid growing concerns over antibiotic contamination.

Precision micro-particle removal from through-holes via laser-induced plasma shockwaves in additive manufacturing

This study introduces a novel Laser-Induced Plasma (LIP) technique for the non-contact, rapid removal of nano and microparticles from through-holes in Additive Manufacturing (AM) components. This method is crucial for high-value applications, such as medical devices, compact heat exchangers, and aerospace engineering, which require efficient cleaning of intricate parts with holes and channels to address high failure costs. The technique leverages shockwaves generated by LIP to target and clean these complex geometries. The research focuses on two main areas: (i) characterizing the effects of shockwaves in semi-cylindrical channels to understand interactions with complex geometries, and (ii) quantitatively analyzing the removal of Fe-271 microparticles from semi-cylindrical channels of silicon (Si) wafers, selected for their consistent surface properties compared to the rough textures of AM-produced surfaces. Utilizing the experimental set-up Laser-Induced Plasma LIP Cleaning for Additive Manufacturing (LIPCAM), the study demonstrates that complete microparticle removal is achievable up to 20 mm from the plasma source with variable laser pulses. The results indicate that particles larger than 27 μm are entirely removed after a single pulse, and particles larger than 21 μm are removed after 50 pulses. These findings highlight the method's effectiveness in achieving high particle removal efficiency across different distances and particle sizes, thus ensuring thorough decontamination of complex internal structures. The study underscores the potential of this method to enhance the reliability and safety of critical AM builds, making it a viable solution for industries where precision and cleanliness are paramount.

The Ultimate Fate of Reactive Dyes Absorbed onto Polymer Beads: Feasibility and Optimization of Sorbent Bio-Regeneration under Alternated Anaerobic–Aerobic Phases

Dyes employed in many production cycles are characterized by high toxicity and persistence in the environment, and conventional wastewater treatments often fail to reach high removal efficiencies. Consequently, there is an increasing research demand aimed at the development of more efficient and sustainable technologies. A two-step strategy consisting of dye sorption followed by sorbent bio-regeneration is proposed here, with a special focus on the regeneration step. The objective of this study was to establish the best operating conditions to achieve regeneration of dye-loaded polymers and concurrently the ultimate removal of the dyes. To this aim, the bio-regeneration of the Hytrel 8206 polymer, used as a sorbent material to remove Remazol Red dye from textile wastewater, was investigated in a two-phase partitioning bioreactor (TPPB) under alternated anaerobic–aerobic conditions. Comprehensive analysis of operational parameters, including sorbent load and initial contamination levels, was conducted to optimize bio-regeneration efficiency. Experimental data demonstrated high regeneration efficiencies (91–98%) with biodegradation efficiencies up to 89%. This study also examines the biodegradation process to investigate the fate of biodegradation intermediates; results confirmed the successful degradation of the dye without significant by-product accumulation. This research underscores the potential of TPPB-based bio-regeneration of polymeric sorbent material for sustainable wastewater treatment, offering a promising solution to the global challenge of dye pollution in water resources.

Development and application of chitosan–urea cotton adsorbent as biomimicry technology inspired by natural predator–prey relationships

Predator-prey interactions play a crucial role in maintaining ecological balance and possibly provide inspiration for strategies to mitigate environmental changes such as harmful algal blooms (HABs). To this end, this study aims to develop a novel strategy to mitigate HABs based on predator–prey interaction, i.e., Daphnia magna and Microcystis aeruginosa interaction. Bio-compounds (urea and 9-octadecenamide) produced by D. magna when encounter M. aeruginosa, were identified, particularly with urea promoting the aggregation of M. aeruginosa. Then, a novel adsorbent against HABs was synthesized by integrating bio-compounds of urea, and its effectiveness in removing M. aeruginosa was demonstrated. Notably, the adsorbent displayed a high removal efficiency of 99.25 % within 6 h. Our eco-friendly strategy holds promise for controlling HABs, representing the successful application of biomimicry principles.

Sustainable solution for wastewater management: Fabrication of cost-effective β-cyclodextrin incorporated chitosan polyvinyl alcohol composite hydrogel film for the efficient adsorption of anionic congo red and tartrazine dyes

Dyes are an integral part of leather, textiles, food, and packaging materials, providing aesthetic appeal to the finished article. These industries use large amounts of water, creating wastewater with harmful, toxic, and hazardous pollutants, posing significant health and environmental risks to the public and ecological system. Therefore, to resolve this issue, a superabsorbent β-cyclodextrin incorporated chitosan polyvinyl alcohol cross-linked with citric acid composite hydrogel film (β-CD/Ch/PVA) has been developed for the effective adsorption of congo red (CR) and tartrazine dyes (TG). The Fourier-transform infrared spectroscopic (FTIR) analysis confirmed the presence of –OH, –NH2 functional groups in hydrogel film. The rough surface morphology was obtained through Field emission scanning electron microscopic (FESEM) analysis. Brunauer-Emmett-Teller (BET) method gave the surface area of hydrogel, which is 17.34 m2/g with pore diameter of 4.12 nm, indicating its mesoporous nature. Adsorption parameters like contact time, temperature, pH, initial concentration of dyes, and dosage of hydrogel have been optimized by batch adsorption studies and the Box-Behknen Design Model. In batch experiments, the hydrogel film effectiveness was confirmed, achieving high removal efficiencies of 95.38 % and 96.3 % for CR and TG dyes at pH 7 and 6, respectively. The adsorption process followed the pseudo-second-order kinetics and Langmuir model at room temperature for both dyes, and the maximum adsorption capacity was found to be 366.34 mg/g, 1436.04 mg/g for CR and TG dyes, respectively. The thermodynamic study revealed that the adsorption of dyes was spontaneous and endothermic in nature. The electrostatic interactions and hydrogen bonding between the hydrogel and dye molecules were responsible for the adsorption. This hydrogel film can be reused for 5 consecutive adsorption–desorption cycles for both dyes, maintaining upto 85 % in removal efficiency. Hence, the synthesized β-cyclodextrin incorporated chitosan polyvinyl alcohol composite hydrogel film holds great potential for the remediation of wastewater effluents and addressing environmental issues.

Influence of Organic Loading Rates on the Treatment Performance of Membrane Bioreactors Treating Saline Industrial Wastewater

This study investigated the efficacy of membrane bioreactor (MBR) technology in treating saline industrial wastewater, focusing on the impact of the organic loading rate (OLR) and the food-to-microorganism (F/M) ratio on treatment performance. This research utilized saline industrial wastewater from Al-Hasa, which had salinity levels ranging from 5000 to 6900 mg/L. It explored treatment processes at varying Chemical Oxygen Demand (COD) concentrations of 800, 1400, and 2000 mg/L, corresponding to an OLR of 0.80 ± 0.05, 1.41 ± 0.07, and 1.98 ± 0.12 g COD/L, respectively. The average F/M ratios used were 0.20, 0.36, and 0.50 g COD/g MLSS·d, maintaining a constant Sludge Residence Time (SRT) of 12 days, a hydraulic retention time (HRT) of 24 h (hrs.), and a flux of 10 L/m2·h. The MBR system demonstrated high COD removal efficiencies, averaging 95.7 ± 1.6%, 95.5 ± 0.4%, and 96.1 ± 0.3%, alongside Biochemical Oxygen Demand (BOD) removal rates of 98.3 ± 0.2%, 99.8 ± 0.1%, and 98.5 ± 0.1%, respectively. However, an increased OLR led to elevated residual COD and BOD levels in the treated effluent, with COD concentrations reaching 34.2 ± 12.8, 63.3 ± 5.9, and 76.5 ± 5.4 mg/L, respectively. This study also reveals a significant decline in ammonia and Total Kjeldahl Nitrogen (TKN) removal efficiencies as OLR increases, dropping from 96.1 ± 0.5% to 80.2 ± 0.9% for ammonia and from 83.8 ± 3.4% to 65.8 ± 2.3% for TKN. Furthermore, higher OLRs significantly contribute to membrane fouling and elevate the transmembrane pressure (TMP), indicating a direct correlation between OLRs and operational challenges in MBR systems. The findings suggest that for optimal performance within the Saudi disposal limits for industrial wastewater, the MBR system should operate at an F/M ratio of ≤0.33 g COD/g of Mixed Liquor Suspended Solid (MLSS)·d. This study underscores the critical role of the OLR and F/M ratio in treating saline industrial wastewater using MBR technology, providing valuable insights for enhancing treatment efficiency and compliance with environmental standards.

Sustainable urea treatment by environmental-friendly and highly hydrophilic vesicle-like iron phosphate-based carbon

Despite the versatile potential applications of urea, its unfavorable characteristics for conventional treatment methods hinder its utilization. Therefore, this study developed vesicle-like iron phosphate-based carbon (IP@C400) as a breakthrough urea removal and recovery material for a wide range of urea-containing sources. IP@C400 rapidly exhibited an exceptional capacity (2242 mg/g in 1 h) across a wide range of pH, even in synthetic hemodialysis wastewater with high urea concentrations and diverse co-existing components, compared with the 60 prominent adsorbents. The adsorption process followed dual Pseudo-kinetic, Langmuir-isotherm models with the involvement of primary robust physical (i.e., H-bonding and electrostatic interaction) and chemical mechanisms (i.e., hydrolysis). Remarkably, IP@C400 can maintain high urea removal (90 %) or recovery efficiency (95 %) even after 10 cycles with minimal leakages of Fe and P (far below WHO and EUWFD standards)—a significant improvement over disposable options. IP@C400 could also perform efficiently on batch and a new approach integrating with a naturally accessible material based on the fixed-bed column using low-range urea realistic samples, achieving 65.2 L water over 10 cycles with undetected urea, neutral pH, and well-aligned water safety standards with a minimal adsorbent dose (0.1 g.L−1) and economical cost ($0.05 L-1). Lastly, its environmentally friendly nature, which contains essential nutrients for plant growth, further enhances its recyclability after release. Thus, IP@C400 offers a solution to environmental sustainability and the urgent ultrapure water issue that industries are facing.