Complex Wastewater Research Articles

A novel multifunctional photocatalytic membrane based on β-FeOOH for oily wastewater purification

In order to deal with the environmental pollution caused by complex oily wastewater, it is necessary to develop filtration membrane materials. However, significant challenges such as poor effect of emulsion separation, limited functionality, and susceptibility to membrane fouling require urgent resolution. Here, we successfully prepared a β-hydroxyl iron oxide/polydopamine-polyethylenimine/polyacrylonitrile (β-FeOOH/PDA-PEI/PAN) nanofiber membrane for treatment of complex wastewater by growing PDA-PEI on a blow-spinning PAN nanofiber membrane and decorating the membrane with β-FeOOH. The porous structure and the large number of hydrophilic groups greatly increase the hydrophilicity of the membrane and give the membrane high permeation fluxes (11531.26 L m−2 h−1) for surfactant-free kerosene-in-water emulsion. The loaded β-FeOOH nanorods increase the roughness of the membrane surface, which enhances the underwater superoleophobic ability of the membrane, and promotes the demulsification of the emulsion and makes it have high separation efficiency of 99.48 % for surfactant-stabilized kerosene-in-water emulsion. In addition, the β-FeOOH/PDA-PEI/PAN also exhibited high organic dye removal efficiency (99.38 %) due to the presence of β-FeOOH. The synergistic effect of low oil adhesion and photocatalysis enhances the antifouling and self-cleaning performances of the material. Significantly, the multifunctional membrane also shows exceptional oil/water separation ability and good stability. The presented synergistic strategy of β-FeOOH/PDA-PEI/PAN membrane materials represents a prospective candidate for the treatment of complex wastewater.

Enhanced detection of glyphosate with a Co-MOF integrated opto-electrochemical sensor

Abstract This study presents a new method for detecting the organophosphorus pesticide glyphosate using advanced scanning electrodes (SPE) and enhanced fluorescence. Metal-organic frameworks from cobalt ions were synthesized using a solvothermal method. It is characterized using Raman spectroscopy, FT-IR, and X-ray diffraction techniques. The electrocatalytic behavior of the materials was studied using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Differential pulse voltammetry (DPV) examined the positive response of plants to glyphosate over a concentration range of 0.55–5.95 mM with a detection limit of 0.334 mM. The fluorescence enhancement ranges from 0.07 mM to 0.67 mM, and the detection limit is 0.0998 mM. Additionally, the selectivity of the proposed opto-electrochemical sensor was evaluated. This selection demonstrates the sensor's ability to detect glyphosate in complex wastewater matrices. This has important implications for environmental monitoring. By addressing glyphosate contamination, the sensor could significantly advance ecological remediation and monitoring strategies. The selectivity, sensitivity, and ability to operate under harsh conditions represent a significant advance in the development of efficient and reliable glyphosate technology for wastewater treatment and environmental protection. In real-sample matrices, the suggested sensor showed a good recovery of the pesticide that had been spiked.

Effect of wastewater containing mixture of nanoparticles on organic matter removal, power generation, and biofilm integrity in sediment microbial fuel cell

ABSTRACT Industrial wastewaters from the cosmetic industry contain high organic strength and mixture of nanoparticles (NPs). Sediment microbial fuel cell (MFC) is an emerging nature-based technology that can treat complex wastewaters. The aim of this study is to understand the effect of a binary mixture of zinc oxide (ZnO) and copper oxide (CuO) NPs (concentration: 1 + 1 and 10 + 10 mg/L) on the organic matter removal, power generation, and biofilm health of sediment MFCs after a long-term operation of 120 days. The high chemical oxygen demand (COD) removal (>95%) observed for all reactors signified the minimal impact of 10 mg/L NP mixture on treatment. The dissolved organic carbon (DOC) removal from the sediment was reduced by 8% due to NPs. NPs also led to 42.2% higher anode extracellular polymeric substances (EPS) and 46.65% lesser cathode EPS generation. The maximum power density of 0.29 mW/m2 was obtained for the 10 mg/L NP reactor, with the average being 23% higher than the no-NP control reactor. This was the first study to explore the effect of the mixture of NPs on the performance of an MFC. The results indicated that sediment MFCs can sustain high mixture concentrations of NPs. Furthermore, variation of parameters can aid in establishing the feasibility of this technology for treating wastewater with NPs.

Effects of Hydraulic Retention Time on Removal of Cr (VI) and p-Chlorophenol and Electricity Generation in L. hexandra-Planted Constructed Wetland-Microbial Fuel Cell.

Hexavalent chromium (Cr (VI)) and para-chlorophenol (4-CP) are prevalent industrial wastewater contaminants that are recalcitrant to natural degradation and prone to migration in aquatic systems, thereby harming biological health and destabilizing ecosystems. Consequently, their removal is imperative. Compared to conventional chemical treatment methods, CW-MFC technology offers broader application potential. Leersia hexandra Swartz can enhance Cr (VI) and 4-CP absorption, thereby improving wastewater purification and electricity generation in CW-MFC systems. In this study, three CW-MFC reactors were designed with L. hexandra Swartz in distinct configurations, namely, stacked, multistage, and modular, to optimize the removal of Cr (VI) and 4-CP. By evaluating wastewater purification, electrochemical performance, and plant growth, the optimal influent hydraulic retention time (HRT) was determined. The results indicated that the modular configuration at an HRT of 5 days achieved superior removal rates and power generation. The modular configuration also supported the best growth of L. hexandra, with optimal photosynthetic parameters, and physiological and biochemical responses. These results underscore the potential of modular CW-MFC technology for effective detoxification of complex wastewater mixtures while concurrently generating electricity. Further research could significantly advance wastewater treatment and sustainable energy production, addressing water pollution, restoring aquatic ecosystems, and mitigating the hazards posed by Cr (VI) and 4-CP to water and human health.

Sm-MOF decorated cotton for efficient on-demand oil-water separation and organic pollutants removal

Complex wastewater containing oil–water and contaminant mixtures is a constant threat to ecosystems and public health. However, efficient water–oil separation and water treatment are required, with a preference for simple but universal matrices for possible large-scale applications. Herein, effective oil–water separation and organic pollutant removal are simultaneously realized on cotton balls decorated with polydimethylsiloxane combined with a samarium metal–organic framework. Cotton balls containing polydimethylsiloxane (10 %) and Sm-MOF (Synthesis temperature was 110 ℃, 15 mg/L) were successfully prepared by a simple precipitation method, with a high water contact angle of 150.75 ± 1.1°. After pre-wetting with a low surface energy solution, the modified cotton was endowed with repeatable super-wetting transitions between superhydrophobic/superoleophilic and superhydrophilic/underwater superoleophobic properties. In addition to on-demand separations of immiscible oil–water mixtures at a rate of 95 %, water-in-oil emulsions could be separated by the addition of different surfactants. The mechanism of demulsification of the treated cotton ball was studied based on the type of emulsifier and the results of emulsified oil separation. Cotton balls modified with 10 % PDMS and Sm-MOF (Synthesis temperature was 140 °C; 15 mg/L) showed higher adsorption capacity compared to pure cotton balls, adsorbing about 98.7 % of Eriochrome Black T within 2 h. Cotton balls modified by PDMS and Sm-MOF are an effective, safe and green material with promising applications in the simultaneous separation of oil–water mixtures and removal of organic pollutants from water systems.

Unraveling nitrogen-doped and vacancy-engineered synergistically modified molybdenum oxide promoting gallium selective adsorption

Sustainable recovery of strategic element gallium from wastewater carries great significance for economic development and environmental conservation. In this study, nitrogen-doped and vacancy-engineered synergistically modified molybdenum oxide nanowires (α-MoOx/N) were rationally designed for efficiently adsorbing gallium ions in the range of 1–200 mg/L under acidic conditions. The introduction of moderate amount of ethylenediamine induced the transition of α-MoOx to the amorphous state. Mixed-valence α-MoOx/N-0.53 (Mo(V) and Mo(VI)) with abundant active sites notably enhanced the adsorption kinetics of gallium ions, accompanied by 98.9 % of gallium ions being adsorbed within 60 min. Advantageously over most gallium adsorbents, α-MoOx/N-0.53 exhibited the maximum adsorption capacity of 464.8 mg/g (298 K), mainly attributed to the synergistic effect of electrostatic adsorption, ion exchange with H+ as well as surface complexation with Mo-O and pyridinic N. Self-enhanced adsorption mechanism and oxygen vacancies as gallium ion adsorption traps in α-MoOx/N-0.53 augmented the opportunities for capturing gallium ions. Excellent selective adsorption of gallium ions from binary and multivariate systems containing Zn2+, Al3+, Cu2+, Ni2+ and robust cyclic stability further endorse α-MoOx/N as the promising candidate for recovering gallium ions from complex wastewater.

Mechanistic Insights into the Removal of Surfactant-Like Contaminants on Mesoporous Polydopamine Nanospheres from Complex Wastewater Matrices.

The detrimental environmental effects of surfactant-like contaminants (SLCs) with distinctive amphiphilic structures have garnered significant attention, particularly since perfluorooctanesulfonate was classified as a persistent organic pollutant. Despite the numerous absorbents developed for SLCs removal, the underlying interaction mechanisms remain speculative and lack experimental validation. To address this research gap, we elucidate the mechanistic insights into the selective removal of SLCs using mesoporous polydopamine nanospheres (MPDA) fabricated via a novel soft-template method. We employed low-field nuclear magnetic resonance to quantitatively characterize the hydrophilicity of the absorbents using water molecules as probes. The results demonstrated that MPDA with uniform mesopores exhibited a remarkable threefold enhancement in SLCs' adsorption capacity compared to conventional polydopamine particles via intraparticle diffusion. We further demonstrated the dominant effects of electrostatic and hydrophobic interactions on the selective removal of SLCs with MPDA by regulating the isoelectric pH value and performing a comparative analysis. The mechanism-inspired SLC-removal strategy achieved an average removal rate of 76.3% from highly contaminated wastewater. Our findings offer new avenues for applying MPDA as an efficient adsorbent and provide innovative and mechanistic insights for targeted SLC removal in complex wastewater matrices.

Selective micropollutants removal in wastewaters by non-radical activation of peroxymonosulfate: Multiparameter analysis of electron-donating capacity

Understanding the electron-donating capacity (EDC) of pollutants in selective advanced oxidation systems is crucial for efficient wastewater decontamination. A novel catalyst, composed of a zeolitic imidazolate framework (ZIF)-derived Co3O4 and carbon nanotubes (CNTs), was synthesized for peroxymonosulfate (PMS) activation. This multiphase PMS activation system efficiently degraded organic pollutants (OPs) with high EDC, indicated by their Hammett constant (σρ) and energy of the highest occupied molecular orbital (EHOMO), achieving a mineralization rate of 83.63 % within 15 min. Singlet oxygen and Co(IV) were identified as the primary reactive species in wastewater decontamination. The electron transfer pathway played a pivotal role in converting Co(II) to Co(IV) and oxidizing OPs. Moreover, the multiphase PMS activation system maintained high activity and selectivity in practical hospital wastewater decontamination. This study offers insights into selective decontamination for complex wastewaters, leveraging the EDC of OPs and the advantages of non-radical-dominated advanced oxidation processes.

Treatment of sludge hydrothermal carbonization wastewater by ferrous/sodium percarbonate system: Effect of wastewater composition and role of coagulation and oxidation

It is crucial to explore the effect of complex wastewater compositions on the ferrous/sodium percarbonate (Fe(Ⅱ)/SPC) system and the role of oxidation-coagulation in designing water treatment processes. This study employed redundancy analysis to investigate the effects of wastewater constituents on oxidation and coagulation. Raman analysis, X-ray Photoelectron Spectroscopy, and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry were used to determine the roles of oxidation and coagulation in the system. The results showed that sulfates and phosphates formed amorphous complexes with iron species via coprecipitation, thereby promoting coagulation to remove organics. Some heavy metals can also be removed by coagulation. The co-activation of SPC by pre-existing transition metals and the added Fe(Ⅱ) facilitated the oxidative removal of organics, while chloride and arsenic were the main inhibitory inorganic substances in the system. Aromatic compounds mainly promoted coagulation, polysaccharides promoted oxidation, humic acid promoted oxidation and coagulation, and C=C/C=O inhibited the Fe(Ⅱ)/SPC system. The oxidation process removed graphitic structures and unsaturated organic matter in the region of (O/C, H/C) = (0.2–0.4, 0.9–2.0) through free radicals and generated amorphous carbon structures and saturated organic matter in the region of (O/C, H/C) = (0.3–0.7, 1.2–1.9). The coagulation process removed aromatic organics with 2–5 rings and unsaturated organics in the region of (O/C, H/C) = (0.2–0.6, 0.7–1.6) with oxygen-containing organics. The combined effects of coagulation and oxidation enhanced the removal efficiency of organic carbon by approximately 40%. This study facilitates the optimization of hydrothermal carbonization wastewater treatment and advanced oxidation processes.

Multifunctional electrospun membranes incorporated with metal oxide nanoparticles, cellulose acetate, and polyvinylpyrrolidone for wastewater treatment: Oil/water separation, dye adsorption, and dye degradation

Multifunctional membranes have gained considerable attention as useful materials for the treatment of complex wastewater that contains dye and oil substances. Electrospun nanofiber membranes (ENM) have substantial advantages and potential for complex wastewater remediation, owing to their unique properties. In this study, an environmentally compatible ENM is fabricated by incorporating photocatalytic metal oxide nanoparticles of zinc oxide (ZnO) or silver-zinc Oxide (Ag-ZnO) into cellulose acetate (CA)/polyvinylpyrrolidone (PVP) nanofibers using electrospinning. Composite membranes ZnO/CA/PVP, Ag-ZnO/CA/PVP, ZnO/DCA/PVP (DCA: deacetylated cellulose acetate), and Ag-ZnO/DCA/PVP (deacetylated) were employed for oil–water emulsion separation, owing to their superhydrophilic and underwater superoleophobic nature, photocatalytic dye degradation due to the presence of ZnO or Ag-ZnO, and dye adsorption resulting from their high surface area. The composite membranes showed more than 95% efficiency for oil/water separation, malachite green adsorption, and photocatalytic methylene blue degradation. These membranes displayed simultaneous oil–water and dye separation efficiency, as well as antibacterial properties. The membrane we present here provides a simple and effective platform for wastewater remediation with a low energy consumption.

Unveiling electron transfer and radical transformation pathways in coupled electrocatalysis and persulfate oxidation reactions for complex pollutant removal

The degradation of multiple organic pollutants in wastewater via advanced oxidation processes might involve different radicals, of which the types and concentrations vary upon interacting with different pollutants. In this study, electrochemical activation of peroxymonosulfate (E/PMS) using advanced activated carbon cloth (ACC) as electrode was applied for simultaneous degradation of mixed pollutants, e.g., metronidazole (MNZ) and p-chloroaniline (PCA). 92.5 % of MNZ and 91.4 % of PCA can be degraded at the cathode and anode at a low current density and PMS concentration, respectively. The rate constants for the simultaneous removal of MNZ and PCA in the E/PMS/MNZ(PCA) system were 118 times and 6 times higher than those in the sole PMS system, and 2.5 times and 1.6 times higher than those in the E/Na2SO4/MNZ(PCA) system, respectively. Different electrochemical characteristics, EPR spectra and radical quenching tests verified that the degradation of MNZ and PCA in the optimal system proceeded primarily through non-radical-dominated oxidation, involving electron transfer and 1O2 effect. The system also exhibited low energy consumption (0.215 kWh/m−3·order−1), broad operational pH range, excellent removal efficiency for water matrix, and low by-products toxicity, indicating its strong potential for practical applications. The ACC, with its super stable, low cost, and electrochemical activity, make it as a promising materials applicable in the E/PMS system for degradation of multiple pollutants. The study further elucidated the mechanism of pollutant interaction with electrode materials in terms of radical and non-radical transformation, providing fundamental insight into the application of this system for treatment of complex wastewater.

Ultrahigh-purity ammonia recovery from synthetic coke wastewater via membrane contactor: Overcoming phenolic interference and assessing cost efficiency

Ammonia recovery from industrial wastewater using membrane contactor processes is emerging as a promising method owing to the diverse applications of ammonia. This study uniquely addressed ammonia recovery from coke plant wastewater, which is challenging due to the presence of numerous toxic and volatile phenolic compounds. Experiments were conducted using a synthetic coke plant effluent to assess the effects of various pH levels and temperatures on ammonia recovery. Specifically, the aim was to achieve high-purity ammonia recovery while minimizing the permeation of phenolic compounds. The results demonstrate that ammonia recovery in the membrane contactor processes is highly efficient, even in the presence of phenolic compounds. During temperature variations at 25 °C and 40 °C, the recovery of ammonia increased from 42.36% to 52.97% at pH 11. Additionally, increasing the pH of a feed solution from 7 to 12 significantly increased the ammonia content to 58.3%. At this pH, the recovered ammonia was of exceptional purity (>99%), with phenol, p-Cresol, and 2,4-xylenol present at negligible concentrations (0.001%, 0.002%, and 0.004%, respectively). This was attributed to the ionization of phenolic compounds at higher pH levels, which prevents their permeation through the hydrophobic membrane. The estimated cost analysis revealed that the membrane contactor process at pH 12 was approximately 1.41 times more cost-effective than conventional air-stripping processes over eight years of operating period (pH-12 membrane contactor: $19.79; pH-12 air stripping: $23.75). This study provides a detailed analysis of the optimal conditions for selective ammonia recovery from complex wastewater, highlighting both effective treatment and sustainable resource recovery and offering a superior alternative to traditional methods.

Co-cultivation of microalgae and bacteria for optimal bioenergy feedstock production in wastewater by using response surface methodology

This work uses response surface methodology (RSM) to study the co-cultivation of symbiotic indigenous wastewater microalgae and bacteria under different conditions (inoculum ratio of bacteria to microalgae, CO2, light intensity, and harvest time) for optimal bioenergy feedstock production. The findings of this study demonstrate that the symbiotic microalgae-bacteria culture not only increases total microalgal biomass and lipid productivity, but also enlarges microalgal cell size and stimulates lipid accumulation. Meanwhile, inoculum ratio of bacteria to microalgae, light intensity, CO2, and harvest time significantly affect biomass and lipid productivity. CO2 concentration and harvest time have significant interactive effect on lipid productivity. The response of microalgal biomass and lipid productivity varies significantly from 2.1 × 105 to 1.9 × 107 cells/mL and 2.8 × 102 to 3.7 × 1012 Total Fluorescent Units/mL respectively. Conditions for optimum biomass and oil accumulation are 100% of inoculation ratio (bacteria/microalgae), 3.6% of CO2 (v/v), 205.8 µmol/m2/s of light intensity, and 10.6 days of harvest time. This work provides a systematic methodology with RSM to explore the benefits of symbiotic microalgae-bacteria culture, and to optimize various cultivation parameters within complex wastewater environments for practical applications of integrated wastewater-microalgae systems for cost-efficient bioenergy production.

Ultra-hydrophilic MOF-303 on electrospun nanofibers with Burr Puzzles structure for the purification of oily wastewater containing heavy metal ions

The current oil-water separation field is extremely complex and the material system is variable. Therefore, the full process applicability of membrane technology is extremely demanding, both in terms of high oil-water separation efficiency and the treatment of soluble substances in wastewater, such as heavy metal ions. The high demand for membrane performance is accompanied by the complexity of the membrane manufacturing process, resulting in the development of membrane technology being hindered. If we can purify heavy metal ions from wastewater while meeting the conditions of oil-water treatment, and simplify the process flow, it is an innovation that we are happy to see. Herein, the use of a seed pre-embedded growth strategy is taking polyacrylamide (PEI) as a breakthrough point, we take advantage of blending to introduce embedding sites in polyacrylonitrile (PAN) membranes. Uniform growth of MOF-303 with Burr Puzzle structure on membrane surface using in situ hydrothermal growth method. The Burr Puzzles structure on the membrane surface is not only able to effectively deal with nanoscale stabilized oil-water mixture and effectively adsorb heavy metal ions, but also enables the MOF-303 crystals to grow more firmly on the membrane surface, so that the modified membrane still maintains good performance in harsh environments. The separation fluxes of the oil-in-water emulsions were all higher than 6987 L m−2 h−1 for oil-in-water emulsion with a separation efficiency of 98.4 %, and the adsorption efficiency of heavy metal ions was also as high as 98.3 %. After 20 cycles, the membrane maintains its promising performance. Due to its simple preparation process and excellent efficiency of emulsions separation and heavy metal ions separation, simplifies complex membrane processes while meeting the rigors of wastewater treatment. it has great prospects for development in the current complex wastewater treatment process.

Long-term performance and activity study of a two-stage anaerobic EGSB reactors system treating complex and toxic industrial wastewater.

Anaerobic treatment of industrial wastewater using upflow anaerobic reactors is an extended trend due to its high efficiency and biogas production potential, but its implementation in some sectors is limited due to the complexity and toxicity of the wastewaters. In this study, a two-stage expanded granular sludge bed (EGSB) reactors system has been investigated at both bench and pilot scale for the treatment of complex and toxic real wastewater from a petrochemical industry. The effect of different operational parameters including organic loading rate (OLR), hydraulic retention time (HRT) and influent characteristics over COD removal and biogas production and composition have been studied. Additionally, biomass specific methanogenic activity (SMA) and wastewater toxicity have been evaluated after long-term operation. Optimum total HRT of 24 h has been determined resulting in total COD and SO4 2- removal of 56.30 ± 5.25% and 31.68 ± 14.71%, respectively, at pilot scale, and average biogas production of 93.47 ± 34.92 NL/day with 67.01 ± 10.23 %CH4 content and 5210.11 ± 6802.27 ppmv of H2S. SMA and toxicity tests have confirmed inhibitory and toxic effects of wastewater over anaerobic biomass with average maximum inhibition of 65.34% in the unacclimated anaerobic inoculum while chronic toxicity produced a decrease of an order of magnitude in SMA after 600 days of operation. This study demonstrates the feasibility of applying an anaerobic treatment to this wastewater using EGSB reactors between a 0.97-1.74 gCOD/L/day OLR range. Nonetheless, periodic reinoculation would be necessary for long-term operation due to chronic toxicity of the wastewater exerted on the anaerobic biomass. PRACTITIONER POINTS: A two-stage EGSB reactors system has been operated at bench and pilot scale to treat complex and toxic petrochemical wastewater. Optimal total HRT of 24 h resulted in average COD removal ranging from 40% to 60%. SMA and toxicity tests have been performed to study long-term acclimation, detecting an activity depletion of an order of magnitude.

Adsorption of ionic contaminants from complex water matrices by versatile chitosan-based beads

Most adsorbents are currently restricted by their single function in pollutant removal from complex wastewater. Herein, we constructed a versatile chitosan-based adsorbent (MC-DA) by grafting amphoteric copolymers with high pH-responsiveness property, aiming at the removal of multiple ionic contaminants. Specifically, the surface charge and hydrophobicity/hydrophilicity of MC-DA can be finely tuned under different pH conditions. As a result, the effective adsorption of cationic methylene blue (MB) and anionic Acid Orange 7 (AO7) with capacities of 627.4 mg/g and 1146.8 mg/g were achieved respectively, superior to most reported materials. Regarding the characterization results, the adsorption mechanisms for MB adsorption were electrostatic and hydrophobic interactions, while the electrostatic attraction was the main driving force for AO7 adsorption. Apart from the versatile adsorption performance, high acid resistance (pH ≥ 2.0), good reusability and rapid separation property under an external magnetic field suggested MC-DA’s promising environmental benefits and practical application potential in water remediation.

Solar powered electrocatalytic treatment of actual human urine coupled with hydrogen production using Ti/MMO for the removal of nitrogen-based compounds

This study addresses a significant micropollutant removal from actual human urine (AHU) through photovoltaic driven electrochemical treatment. This study showed significant reductions of 69.09 % urea, 67.95 % creatinine, and 95.180 % uric acid under optimal continuous recirculation conditions. Analysis revealed that the degradation of pollutants were facilitated by in-situ generation of reactive oxygen and chlorine species during treatment. Further, the procedure employed with molecular hydrogen generation during anodic oxidation as useful byproduct. Thus, the findings suggest that novel mixed metal oxide exhibits high efficacy for AHU treatment, offering a prominent concept for onsite treatment of complex mixed wastewater in real-life applications.

Removal of quinoline in aqueous solutions using chemically modified and unmodified hydrochars from lotus seedpods: A comprehensive experimental study

In this study, a novel hydrochar adsorbent derived from lotus seedpods was synthesized and subsequently modified to enhance its adsorption efficiency for quinoline contaminated wastewater. Using lotus seedpods as biomass raw material, lotus seedpod hydrochar (LSH) was prepared by hydrothermal carbonization method, and it was modified with hydrochloric acid (HA) and phosphoric acid (PA) as modifiers to improve adsorption efficiency. The adsorption kinetics and isotherms of quinoline on both the unmodified and modified hydrochars were studied in detail to elucidate the underlying adsorption mechanisms. Furthermore, the effect of coexisting organic pollutants, i.e. phenol and pyridine, commonly found in coking effluents, on the quinoline adsorption efficiency of hydrochar was investigated. The regenerative potential of the adsorbent was explored through desorption studies to assess the reusability and practicality of hydrochar post-adsorption. The optimal conditions for modified LSH were determined as follows: an adsorbent dosage of 3 g/L, pH of 3, an initial quinoline concentration of 200 mg/L, and a contact time of 90 minutes. The maximum adsorption capacities for PA-LSH and HA-LSH were 48.59 mg/g and 49.12 mg/g, respectively. Among the types of modification agents, acid modifiers, particularly 20 % phosphoric acid and 20 % hydrochloric acid, significantly enhanced the adsorption efficiency, increasing the adsorption rates by 24.24 % and 14.56 %, respectively, compared to unmodified hydrochar (64.06 %). Coexisting pollutants minimally affected quinoline adsorption, with phosphoric acid-modified hydrochar maintaining 80.33 % removal in simulated coking wastewater. Regeneration with hydrochloric acid showed improved utility, with modified hydrochar sustaining over 80 % adsorption after three cycles. This research not only presents an innovative approach to the development of efficient adsorbents for quinoline removal, but also provides insight into the adsorption behavior of hydrochar in the complex wastewater systems. The findings contribute to both the advancement of sustainable water treatment technologies and the use of biomass-derived materials for environmental remediation. As such, this work holds promise for applications in wastewater treatment and environmental remediation.

Layer-by-layer adsorption behavior of Cr(VI) on MoS2@Mt induced by sulfamethoxazole

Hexavalent chromium (Cr(VI)) contamination in wastewater is a serious environmental threat. Cr(VI) removal is often interfered by antibiotics in wastewater, however, the underlying mechanism remains unclear. Here, molybdenum disulfide/montmorillonite (MoS2@Mt) composites were prepared and used for Cr(VI) removal to reveal the adsorption behavior of Cr(VI) on MoS2@Mt induced by sulfamethoxazole. The induction effect of the typical antibiotic sulfamethoxazole (SMX) was investigated. The adsorption capacity of MoS2@Mt was maximum at pH 2 and decreased with increasing pH. The performance results showed that SMX promoted Cr(VI) removal, with a maximum increase of 14.80 % in removal efficiency. Cr(VI) adsorption on MoS2@Mt followed the Langmuir model, whereas it was more consistent with the Freundlich model in the presence of SMX. This suggested that SMX induced a monolayer to multilayer shift in Cr(VI) adsorption. XPS results indicated that Cr(VI) removal pathways included Cr(VI) adsorption, chemical reduction of Cr(VI) to trivalent chromium (Cr(III)), and Cr(III) chelation. In particular, electrostatic pulling, coordinated adsorption, and hydrogen bond attraction contributed to Cr(VI) adsorption. Mechanism investigation suggested that Cr(VI) or SMX absorbed on the material surface continued to absorb SMX or Cr(VI) by electrostatic attraction, resulting in layer-by-layer adsorption behavior, which facilitated Cr(VI) removal. In actual wastewater treatment, MoS2@Mt reduced Cr(VI) concentrations (0.15–5 mg/L) to below the World Health Organization standard of 0.05 mg/L in the presence of 0.32 mg/L SMX. Overall, this study revealed the mechanism of SMX-induced Cr(VI) adsorption behavior, which favors the elimination of Cr(VI) from real complex wastewater.

A self-driven solar coupling system with activated carbon felt cathode for resourcefully purifying uranium and organic contaminated water

With the continuous development of nuclear energy, it becomes increasingly important to recover uranium from the radioactive wastewater, in which various organics may combine with uranyl ions (UO22+) to form refractory complexes. Developing highly active cathode materials for uranium reduction is essential to improve the performance of self-driven solar coupling system (SSCS) in treating complex radioactive wastewater. In this study, an activated carbon felt (ACF) cathode is prepared by anodizing carbon felt (CF) in NaOH solution to adjust the surface morphology and functional groups. The ACF is then used in a SSCS combined with a TiO2 nanorods array (TNA) photoanode for the efficient recovery of uranium and the rapid degradation of organic pollutants with simultaneous electricity generation. Compared to CF, the functionalized ACF with oxygen-containing functional groups, provides sufficient sites for UO22+ adsorption and facilitates the charge separation. The SSCS with the ACF cathode exhibits removal ratios of approximately 99.9 % for tetracycline hydrochloride (TCH) and UO22+, with removal rates of ∼ 0.025 and ∼ 0.154 min−1, respectively. In contrast, the SSCS with the CF cathode achieves removal rates of ∼ 0.006 and ∼ 0.026 min−1. Additionally, a maximum power density of 0.94 mW·cm−2 with a fill factor of 23.36 % is achieved. After 20 cycles, the system maintains removal ratios of 99.1 % for TCH and 98.2 % and UO22+. Intensive investigation also reveals that the system functions robustly in treating complex wastewater with a complicated condition of pH, co-exited ions, and various pollutant concentrations. Furthermore, efficient removal of organics and uranium is also achieved from polluted seawater or under real sunlight illumination. This paper presents a simple method to prepare low-cost, highly active and stable cathodes for uranium reduction in an easy-to-operated, energy-saving and economical solar-driven system.