Removal Of Organic Contaminants Research Articles

When covalent organic frameworks meet zeolites: Enhancing rhodamine B removal through the synergy in the emerging organic–inorganic nanoadsorbents

The development of new porous materials has attracted intense attention as adsorbents for removing pollutants from wastewater. However, pure inorganic and organic porous materials confront various problems in purifying the wastewater. In this work, we integrated a covalent organic framework (TpPa-1) with an inorganic zeolite (TS-1) for the first time via a solvothermal method to fabricate new-type nanoadsorbents. The covalent organic framework/zeolite (TpPa-1/TS-1) nanoadsorbents combined the merits of the zeolite and COF components and possessed efficient adsorptive removal of organic contaminants from solution. Structural morphology and chemical composition characterization by powder X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and thermogravimetric analysis demonstrated the successful preparation of TpPa-1/TS-1 composite nanoadsorbents. The resultant composite adsorbent TpPa-1/TS-1 removed rhodamine B at 1.7 and 2.6 times the efficiency of TpPa-1 and TS-1, respectively. Additional investigation revealed that the Freundlich adsorption isotherm and the pseudo-second-order kinetic model could be employed to represent the adsorption process more appropriately. Thermodynamic calculation analysis showed that the adsorption process proceeded spontaneously and exothermically. Besides, the effects of pH, absorbent mass and ionic strength on the adsorption performance were systematically investigated. The prepared composite adsorbent showed a slight decrease in removal efficiency after eight cycles of repeated use, and real water environment experiments also showed the high stability of the adsorbent. The enhanced performance can be attributed to electrostatic interaction, acid-base interaction, hydrogen bonding and π–π interactions.

Engineered design of MnFe2O4/CoNiFe-LTH/g-C3N4 heterocatalyst for doxycycline degradation via Fenton oxidation process: Optimization and mechanism

The removal of organic contaminants from waterways is vital to the ecosystem. A novel MnFe2O4/CoNiFe-LTH/g-C3N4 catalyst was synthesized via self-assembly preparation and linked with H2O2 for the Fenton degradation of doxycycline (DXY). The MnFe2O4/CoNiFe-LTH/g-C3N4 was characterized using FTIR, XRD, XPS, VSM, SEM, GC-MS, and ICP-OES. Interestingly, the magnetically separable and high-stability catalyst achieved 89.11% DXY degradation, and 69.30% TOC removal efficiency within 60 and 120 min, respectively (at pH = 7.5, catalyst dosage= 0.01g, H2O2 = 400 ppm, T= 20 °C, and DXY concentration= 100 ppm). In addition, the synergistic effect of metal cations (Co, Ni, Fe, and Mn) triggered Fenton degradation through a continuous closed cycle of electrons. A pseudo-first-order kinetic model also fitted DXY degradation with MnFe2O4/CoNiFe-LTH/g-C3N4. Furthermore, the radical pathway mechanism was confirmed with XPS before and after degradation and with radical scavenging tests. The DXY degradation pathway was speculated by GC-MS analysis. Quantitative structure-activity relationship (QSAR) was applied to assess intermediates for developmental toxicity. The MnFe2O4/CoNiFe-LTH/g-C3N4 catalytic activity on H2O2 decomposition was determined via titrimetric analysis. Recycling tests and ICP-OES measurements were further used to investigate the catalyst's resilience and reusability. Besides, MnFe2O4/CoNiFe-LTH/g-C3N4 demonstrated a performance of 70% over eight catalytic degradation runs with minimal metal leaching. Eventually, MnFe2O4/CoNiFe-LTH/g-C3N4 is a viable catalyst for breaking down organic contaminants in wastewater.

Sustainable electro-Fenton simultaneous reduction of Cr (VI) and degradation of organic pollutants via dual-site porous carbon cathode driving uncoordinated molybdenum sites conversion

Simultaneous removal of heavy metals and organic contaminants remains a substantial challenge in the electro-Fenton (EF) system. Herein, we propose a facile and sustainable “iron-free” EF system capable of simultaneously removing hexavalent chromium (Cr (VI)) and para-chlorophenol (4-CP). The system comprises a nitrogen-doped and carbon-deficient porous carbon (dual-site NPC-D) cathode coupled with a MoS2 nanoarray promoter (MoS2 NA). The NPC-D/MoS2 NA system exhibits exceptional synergistic electrocatalytic activity, with removal rates for Cr (VI) and 4-CP that are 20.3 and 4.4 times faster, respectively, compared to the NPC-D system. Mechanistic studies show that the dual-site structure of NPC-D cathode favors the two-electron oxygen reduction pathway with a selectivity of 81 %. Furthermore, an electric field-driven uncoordinated Mo valence state conversion of MoS2 NA enchances the generation of dynamic singlet oxygen and hydroxyl radicals. Notably, this system shows outstanding recyclability, resilience in real wastewater, and sustainability during a 3 L scale-up operation, while effectively mitigating toxicity. Overall, this study presents an effective approach for treating multiple-component wastewater and highlights the importance of structure-activity correlation in synergistic electrocatalysis.

Graphene oxide–carbon nanotube composite membrane for enhanced removal of organic pollutants by forward osmosis

Composite membranes constructed using both graphene oxide and carbon nanotubes (CNTs) were designed to strengthen the forward osmosis (FO) technology for the removal of organic contaminants. The nano-membrane was chemically treated with organic acids, which were citric acid in this case for more efficiency in permeability and pollutant removal. The efficiency of the composite membranes in organic pollutants removal was estimated by checking the levels of COD (chemical oxygen demand), TKN (total nitrogen analysis), and (TOC) organic carbon in the water sample before and after applying the technology. The analysis of the study recommends that the nano-membranes may be appropriately used to reduce organic pollutants significantly, to 98.20% efficiency, in addition to elevating water quality standards. This was caused by the higher degree of selectivity and permeability of the membranes that was consequent to the treatment of the organic acid. In brief, the employment of citric acid in the pre-treatment procedures for the preparation of composite graphene oxide-carbon nanotube membranes for FO technology could take water cleaning technologies a step ahead toward sustainable technology. The application of the composite membrane with graphene oxide and carbon nanotubes is not only efficient in cleaning out organic contaminants but it has a lot of added benefits. These membranes are easily manufactured with a long lifespan which, in turn, makes them cost-effective and environmentally friendly. Also, forward osmosis technology reduces the energy demand compared to other water remediation methods, making it a more sustainable solution. The final point of this article is that the using of composite graphene oxide-carbon nanotube membranes treated with an organic acid, such as citric acid, in FO technology not only assists with the water treatment problem but also elevates sustainablility due to its effectiveness and is environmentally friendly.

Energy-efficient Treatment of Refractory Industrial Effluent Using Flow-through Electrochemical Processes: Oxidation Mechanisms and Reduction of Chlorinated Byproducts

While flow-through anodic oxidation (FTAO) technique has demonstrated high efficiency to treat various refractory waste streams, there is an increasing concern on the secondary hazard generation thereby. In this study, we developed an integrated system that couples FTAO and cathodic reduction processes (termed FTAO-CR) for sustainable treatment of chlorine-laden industrial wastewater. Among four common electrode materials (i.e., Ti4O7, β-PbO2, RuO2, and SnO2-Sb), RuO2 flow-through anode exhibited the best pollutant removal performance and relatively low ClO3 and ClO4 yields. Because of the significant scavenging effect of Cl− in real wastewater treatment, the direct electron transfer process played a dominant role in contaminant degradation for both active and nonactive anodes though active species (i.e., active chlorine) were involved in the subsequent transformation of the organic matter. A continuous FTAO-CR system was then constructed for simultaneous COD removal and organic and inorganic chlorinated byproduct control. The quality of the treated effluent could meet the national discharge permit limit at low energy cost (~4.52 kWh m3 or ~0.035 kWh g1-COD). Results from our study pave the way for developing novel electrochemical platforms for the purification of refractory waste streams whilst minimizing the secondary pollution. Environmental ImplicationsIndustrial wastewater usually features high organic matter content and complex composition, posing a significant environmental risk. While anodic oxidation has demonstrated high efficiency, there is increasing concern on the secondary hazard generation thereby. An energy-efficient system coupling flow-through anodic oxidation and cathodic reduction processes is therefore proposed, achieving simultaneous organic contaminant removal and chlorinated byproduct control. The direct electron transfer process imparts an advantage in treating chlorine-laden wastewater compared to the •OH-based advanced oxidation counterparts. The results of this study pave the way for developing novel electrochemical platforms for the purification of refractory waste streams whilst minimizing the secondary pollution.

Flow Rate and Kinetics of Trace Organic Contaminants Removal in Black Carbon-Amended Engineered Media Filters for Improved Stormwater Runoff Treatment

Urban stormwater runoff is considered a key component of future water supply portfolios for water-stressed cities. Beneficial use of runoff, such as capture for recharge of drinking water aquifers, relies on improved stormwater treatment. Many dissolved constituents, including metals and trace organic contaminants (TrOCs) such as hydrophilic pesticides and poly- and perfluoroalkyl substances (PFASs), are of concern due to their toxicity, persistence, prevalence in stormwater runoff, and poor removal in conventional stormwater control measures. This study explores the operational flow rate limitations of black carbon (BC)-amended engineered media filters for removal of a wide suite of dissolved metals and TrOCs and provides validation for a previously developed predictive TrOC transport model. Column experiments were conducted with face velocities of 40 and 60 cm h−1 to assess Douglas Fir-based biochar and regenerated activated carbon (RAC) filter performance in light of media-contaminant removal kinetic limitations. This study found that increasing the face velocity in BC-amended filters to 40 and 60 cm h−1, which are representative of field conditions, decreased the removal of total suspended solids, turbidity, dissolved hydrophilic TrOCs, and PFASs when expressed as volume treated relative to previous studies conducted at 20 cm h−1. Dissolved metals and hydrophobic TrOCs removal were not substantially affected by the increased flow rates. A predictive 1-d intraparticle pore diffusion-limited sorption model with sorption and effective tortuosity parameters determined previously from experiments conducted at 20 cm h−1 was validated for these higher flow rates. This work provides insights to the kinetic limitations of contaminant removal within biochar and RAC filters and implications for stormwater filter design and operation.

2D Cobalt-carbon–nitrogen loaded 3D Prussian blue analogues enhances peroxymonosulfate activation for bisphenol A Degradation: Singlet oxygen dominated nonradical pathway

Singlet oxygen (1O2) dominated peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) is an effective technology for the removal of electron-rich organic contaminants. However, the highly selective generation of 1O2 is limited by the development of catalysts. Herein, a two-dimensional (2D) cobalt-carbon–nitrogen loaded three-dimensional (3D) Prussian blue analogue (CoCN@PBA-P) material was synthesized by the one-step method using hematite with different morphologies as the precursor. The two atomically dispersed Co sites in three CoCN@PBA-P were demonstrated that could effectively activate PMS to degrade bisphenol A (BPA) in different and complex environmental backgrounds. The quenching, probe quantitative, and EPR results indicated the dominant role of 1O2 in CoCN@PBA-P/PMS system, and the steady-state concentration of 1O2 can achieve 4.0 × 10-9-1.3 × 10-8 M. Importantly, the role of Co as the active site was verified by screening experiments, and the mechanism of CoCN@PBA-P activate PMS was revealed by experimentally and theoretically, and the pathway to generate 1O2 is *HSO5→*SO4+OH–→*SO4+*OH→*O→1O2 (* represents that the species is bound to the active site). Finally, the analysis of degradation intermediates and their toxicity showed that the whole process is harmless to the environment. This work provides a new perspective to the design of 2D@3D materials and their application in PMS-based AOPs.

Bamboo leaf-derived biochar/iron silicate composite for an adsorption-degradation synergistic removal of ciprofloxacin

Antibiotics pose significant risks to both the environment and human health. Herein, we develop a collaborative strategy for the enhanced removal of a typical antibiotic, Ciprofloxacin (CIP), by using a bamboo leaf-derived biochar/iron silicate composite (BL-FeSi) with the assistance of peroxymonosulfate (PMS). The rationale behind the design is the construction of composited material with synergistic adsorption-catalysis functions, based on covalent bonding networks of the biochar and specific Fe(III)/Fe(II) redox chemistry of iron silicate in PMS activation system. H2 reduction of pristine BL-FeSi increases Fe(II) content and thus improves catalytic activity. Batch experiments demonstrate that the preferred BL-FeSi400 (H2 treatment at 400 °C) exhibits superior efficiency in activating PMS. The CIP removal efficiency is highly dependent on pH value of reaction solution. A remarkable 97% removal is achieved at pH = 5.5 (CIP: 60 mL, 20 mg/L; BL-FeSi400: 0.2 g/L, PMS: 0.2 g/L), and the pH increase to 11 results in 100% CIP removal. The BL-FeSi400 shows robust resistance to inorganic ions (NO3−, SO42−, HCO3−, and H2PO4−), and the catalytic activity remains consistently high (>82%) even after four consecutive cycles, making it highly promising for practical applications. It is found that both radical pathway (•OH and SO4•−) and non-radical pathway (1O2) contribute to CIP degradation in the BL-FeSi400/PMS system, while the active •OH dominates the oxidization process. The coupling of adsorption and degradation holds great potentials for effective removal of more organic contaminants.

Mixed (organic and inorganic) contaminants removal ability of water fern biomass-based biochar on starch industry wastewater

Mixed (organic and inorganic) contaminants removal ability of water fern biomass-based biochar on starch industry wastewater

Predicting removal efficiency of organic pollutants by soil vapor extraction based on an optimized machine learning method

Soil vapor extraction (SVE) was a cost-effective technology for remediating volatile and semi-volatile organic contaminated soils. Many factors, including SVE parameters, soil properties, and contaminant characteristics, significantly influenced the remediation efficiency of SVE. The optimal conditions for organic pollutants removal efficiency were site-specific and varied among studies. Therefore, a generalized model was needed to predict the remediation efficiency of SVE in organic contaminated soils. This study employed machine learning to predict the removal efficiency of organic pollutants by SVE. The model's development was based on a trainset, and its predictive capabilities were evaluated using a testset. An XGBoost (XGB) model was derived from literature data (R2 = 0.9728). Time, pollutant type, and temperature were identified as the three most important features affecting SVE remediation efficiency. The accuracy (R2 = 0.9799) and universality of the model were enhanced through an optimization scheme. The developed XGB model demonstrated the ability to predict the removal efficiency of organic pollutants by considering all collected influential factors. The mechanism of multi-factor interaction on remediation efficiency was clarified. Overall, this study would contribute to evaluating the remediation potential of SVE for specific organic contaminated soils, aiding in maximizing the removal efficiency of organic pollutants under optimal conditions.

Substrate promiscuity of xenobiotic-transforming hydrolases from stream biofilms impacted by treated wastewater

Organic contaminants enter aquatic ecosystems from various sources, including wastewater treatment plant effluent. Freshwater biofilms play a major role in the removal of organic contaminants from receiving water bodies, but knowledge of the molecular mechanisms driving contaminant biotransformations in complex stream biofilm (periphyton) communities remains limited. Previously, we demonstrated that biofilms in experimental flume systems grown at higher ratios of treated wastewater (WW) to stream water displayed an increased biotransformation potential for a number of organic contaminants. We identified a positive correlation between WW percentage and biofilm biotransformation rates for the widely-used insect repellent, N,N-diethyl-meta-toluamide (DEET) and a number of other wastewater-borne contaminants with hydrolyzable moieties. Here, we conducted deep shotgun sequencing of flume biofilms and identified a positive correlation between WW percentage and metagenomic read abundances of DEET hydrolase (DH) homologs. To test the causality of this association, we constructed a targeted metagenomic library of DH homologs from flume biofilms. We screened our complete metagenomic library for activity with four different substrates, including DEET, and a subset thereof with 183 WW-related organic compounds. The majority of active hydrolases in the metagenomic library preferred aliphatic and aromatic ester substrates while, remarkably, only a single reference enzyme was capable of DEET hydrolysis. Of the 626 total enzyme-substrate combinations tested, approximately 5% were active enzyme-substrate pairs. Metagenomic DH family homologs revealed a broad substrate promiscuity spanning 22 different compounds when summed across all enzymes tested. We biochemically characterized the most promiscuous and active enzymes identified based on metagenomic analysis from uncultivated Rhodospirillaceae and Planctomycetaceae. In addition to characterizing new DH family enzymes, we exemplified a framework for linking metagenome-guided hypothesis generation with experimental validation. Overall, this study expands the scope of known enzymatic contaminant biotransformations for metagenomic hydrolases from WW-receiving stream biofilm communities.

Efficient activation of periodate using MnFe2O4/BC composite for removal of organic contaminants: Performance and mechanism

The periodate (PI)-based advanced oxidation process (AOP) is an economical and energy-saving method for remediating water by degrading pollutants. An efficient system for PI activation was developed by loading manganese ferrite spinel (MnFe2O4) on biochar (BC) through a facile method, affording a metal-oxide MnFe2O4/BC composite catalyst. The developed system demonstrated significant effectiveness in eliminating various organic pollutants, particularly achieving high removal (5.26 and 2.83 times that of biochar and MnFe2O4, respectively) and mineralization (49.7 %) of the model pollutant tetracycline hydrochloride (TC) within 30 min. The system exhibited outstanding catalytic performance under various environmental conditions (pH, inorganic salts, humic acid, and real water bodies), as evidenced by quenching experiments and electron paramagnetic resonance (EPR) studies, proving that superoxide radicals (O2•-) are the main reactive species for TC degradation in the reaction system, in addition to singlet oxygen (1O2), iodyl radicals (IO3•) and hydroxyl radicals (•OH). Potential pathways for TC degradation in this system were revealed based on density functional theory (DFT) and the ecological toxicity of the intermediates was analyzed through quantitative structure–activity relationship (QSAR) assessment. Analysis of the magnetic hysteresis and cycling stability demonstrated that the composites were stable and could be recycled by applying a magnetic field. This work opens a new pathway for designing efficient PI activators for the selective oxidation of organic pollutants and highlights the potential application of this system in practical wastewater treatment.

Porous sulfur polymers for effective aqueous-phase organic contaminant removal

Sulfur polymers produced through 'inverse vulcanization' exhibit various attributes, such as photocatalytic activity and a high capacity to adsorb heavy metals. Nevertheless, there is a lack of research investigating the use of sulfur polymers as materials for the removal of organic contaminants. In this work, porous sulfur polymers (PSPs) were synthesized from elemental sulfur and 1,3-diisopropenylbenzene, with porosity introduced via salt templating. The result is a material that can strongly adsorb and chemically neutralize a model organic contaminant (caffeine). PSPs show adsorption up to 5 times higher than a leading adsorption material (activated carbon). Furthermore, either the adsorption or degradation processes can govern the removal efficiency depending on the synthesis parameters of PSPs. This is the first-ever report demonstrating sulfur polymers as effective materials for removing emerging contaminants from water. The versatile synthesis of sulfur polymers offers variation, which means that there is much more to explore in this exciting research area.

Machine learning modeling of fluorescence spectral data for prediction of trace organic contaminant removal during UV/H2O2 treatment of wastewater

Dynamic feedback of the removal performance of trace organic contaminants (TrOCs) is essential towards economical advanced oxidation processes (AOPs), whereas the corresponding quick-response feedback methods have long been desired. Herein, machine learning (ML) multi-target regression random forest (MORF) models were developed based on the fluorescence spectra to predict the removal of TrOCs during UV/H2O2 treatment of municipal secondary effluent as a typical AOP. The predictive performance of the developed MORF model (R2 = 0.83-0.95) exhibited higher accuracy over the traditional linear regression models with R2 increased by ∼0.15. Furthermore, through feature importance analysis, the spectral regions of high importance were identified for different groups of TrOCs, thus enabling faster data acquisition due to remarkably reduced size of required fluorescence spectral scanning region. Specifically, the fluorescence regions Ex(235-275 nm)/Em(325-400 nm) and Ex(240-360 nm)/Em(325-450 nm) were found highly correlated with the removal of the TrOCs susceptible to both photodegradation and •OH degradation and those primarily subject to •OH degradation, respectively. In addition, the spectral regions of high importance were also individually identified for the investigated TrOCs during the AOP. Through providing an efficient ML-based feedback method to monitor TrOC removal during AOP, this study sheds light on the development of dynamic feedback-based strategies for precise and economical advanced treatment of wastewater.

Heat and mass transfer based on the low-temperature thermal treatment of hydrocarbons-impacted soil: A numerical simulation and sandbox validation

Thermal treatment can be an effective method for soil remediation, and numerical models play a crucial role in elucidating the underlying processes that affect efficacy. In this study, experiments were conducted to examine the low-temperature thermal treatment for removing n-hexane and n-octane from soil. The results showed that the removal of two alkanes followed the pseudo-first-order kinetics. Additionally, a quantitative relationship between kinetics constant and temperature was established. Based on experimental results, a simple mathematical model was presented via COMSOL Multiphysics 6.0. The processes considered in the model incorporated conductive and convective heat transfer, the vaporization latent heat, and the removal of organic contaminants which was quantified using an advection-dispersion equation combined with a pseudo-first-order kinetic. The developed model was first validated by a thermal treatment in a soil column, demonstrating conformity with the measured temperature and concentration values. Subsequently, the temporal and spatial changes in soil temperature and contaminant levels were evaluated for different heating temperatures. It was found that thermal conduction dominated heat transfer, whereas thermal convection caused by the migration of liquid water intensified when the temperature was higher than the boiling point. The completion time exhibited a correlation with the heating temperature. It was predicted that the time required to achieve a 90% removal efficiency could be shortened from 14 h to 9.5 h by elevating the heating temperature from 80 ℃ to 120 ℃. The study also investigated the impact of the initial water content on heat transfer. It was observed that the saturated soil showed the slowest heating rate and the longest boiling stage.

A visible light driven photocatalyst Ag/AgBr/SrSb2O6 for removal of model organic contaminants and hexavalent chromium

A single plausible solution to multi-environmental issues is an efficient photocatalyst. The SrSb2O6 with a band gap of 2.72 eV was successfully tailored to 1.99 eV by deposition of Ag/AgBr. The synergistic effect of reduced band gap and surface plasmon resonance (SPR) effect of Ag0 could enhance the photocatalytic efficiency to a greater extent. This work attempts to explore a composite photocatalyst Ag/AgBr/SrSb2O6 for the photodegradation of organic wastes such as dyes, organic solvents, drugs, and antibiotics. In addition, the photo remediation of heavy metal waste such as Cr6+ is also investigated. The propitious results promise Ag/AgBr/SrSb2O6 to be a wide-range photocatalyst that can eliminate both organic and inorganic waste from water. The photodegradation of RhB dye, phenol, and tetracycline reached up to 80.8%, 76.8%, and 64.5%, respectively. Notably, the Ag/AgBr/SrSb2O6 catalyst effectively converted 97.3% of lethal Cr6+ to benign Cr3+. The better electron hole pair separation of the composite was evidenced by PL spectra.

Zeta potential characterization of the effects of fouling and cleaning of hollow fibre forwards osmosis membrane modules

Commercial Aquaporin Inside® hollow fibre forward osmosis (HFFO) membranes embedded in lab-scale filtration modules were employed to study their fouling propensity during forward osmosis (FO) up-concentration of a fermentation broth resulting from vaccine production. The fouling and subsequent cleaning processes were analysed in terms of the lumen side active layer zeta potential of the HFFO membranes. The zeta potential indicated significant adsorption of contaminants from the feed solution on the membrane's active surface. Various cleaning conditions: alkaline, alkaline + surfactant, complexation and acidic (hydrochloric and citric), were used to investigate the potential enhancement of contaminant removal compared to a simple rinse with deionized water. Despite a full recovery of the membrane performance after cleaning, the zeta potential measurements indicated contaminants remaining on the membrane surface. The extent of this residual contamination depends strongly on the applied cleaning conditions. Rinsing with deionized water and alkaline cleaning (with or without surfactant) results in a shift in the fouled membrane isoelectric point (IEP) with a concomitant shift of the zeta potential towards the IEP and zeta potential of the pristine membrane. However, cleaning with either the complexation agent or under acidic conditions exhibits a more negative zeta potential of the fouled HFFO membranes compared to the pristine membrane, indicating an additional effect superimposed on the removal of organic contaminants.

Novel solar-induced wastewater purification materials originated from ore tailing solid waste

Ore tailings (OT) are solid waste produced as a by-product of the mining industry, posing serious environmental challenges. Ensuring the low-carbon and environmentally friendly development of mineral raw materials, enhancing the reclamation, reuse and recycling rate of raw materials in the full lifecycle, presents a significant challenge. To achieve high-value utilization of OT and solve the problem of clean water supply, a novel solar evaporation wastewater purification material was developed using modified ore tailing/acrylate composite photothermal coating. The photothermal functional modified ore tailings (OT@PDA@CB) were fabricated by grafting carbon black (CB) and polydopamine (PDA) onto the OT surface through the physical adhesion of active chemical groups, synergistically enhancing broadband light absorption ability of OT@PDA@CB/acrylate coating. UV–Vis-NIR spectra showed increased absorption in visible and near-infrared (NIR) light. Surface temperature of OT@PDA@CB/acrylate coating under 1200 W/m−2 illumination increased to 65.6 °C compared with 52.6 °C of OT/acrylate coating due to increased light absorption, resulting in an evaporation rate of 0.89 kg·m−2·h−1 within 1 h. The solar evaporation efficiency for OT@PDA@CB evaporator was 48.3%, which was 192.7% higher than that in blank acrylate sample. The obtained OT@PDA@CB/acrylate composite photothermal coating demonstrated versatile abilities for desalination, heavy-metal purification and organic contaminant removal. This work offers a straightforward approach for high-value utilization of inexpensive mineral solid wastes and green solar-induced wastewater purification technique.

Tunning MIL-101(Cr) MOF polymorphism towards efficient adsorption and localized Fenton-like degradation of para-nitroaniline by Fe incorporation

The employment of metal–organic frameworks (MOFs) in the context of eliminating organic contaminants from water has garnered significant interest in contemporary research. This study investigated the impact of varying quantities of iron on the MIL-101(Cr) adsorbent. For the first time, a polymorphic Cr/Fe-MOF was utilized for the adsorption and localized Fenton-like degradation of p-nitroaniline (PNA). Importantly, the Fe centers exhibited a ternary role of (i) transforming MIL-101 into MIL-53lt morphology, (ii) boosting PNA adsorption on the MIL(Cr) material, and (iii) enabling the Fenton-like decomposition of the adsorbed PNA in reduced solution volume. Cr:Fe(50:50) exhibited the highest adsorption capacity of 378.9 mg/g, notwithstanding its smaller surface area (SBET = 8.9 m2/g). Overall, adsorption kinetics and isotherms correlated better with pseudo-second-order and Langmuir models, respectively. The adsorption mechanism was attributed to breathing effect, H-bonding and π-π interaction. Besides, PNA degradation kinetics stood at 0.21 min−1, and the reactive oxygen species were identified as •OH, •O2– and 1O2. During continuous removal of PNA, the Cr:Fe(50:50) MOF immobilized onto cotton met the environmental discharge standard (1 mg/L) up to 52 bed volumes (initial P = 10.0 mg/L at 1 mL/min). This study not only presents a superior polymorphic MOF adsorbent but also promotes the fabrication of localized Fenton-like catalysts for the removal of organic contaminants in wastewater.

Insight into roles of carbon anodes for removal of refractory organic contaminants in electro-peroxone system: Mechanism, performance and stability

Electro-peroxone (EP) is a novel technique for the removal of refractory organic contaminants (ROCs), while the role of anode in this system is neglected. In this work, the EP system with graphite felt anode (EP-GF) and activated carbon fiber anode (EP-ACF) was developed to enhance ibuprofen (IBP) removal. The results showed that 91.2% and 98.6% of IBP was removed within 20 min in EP-GF and EP-ACF, respectively. Hydroxy radical (O⋅H) was identified as the dominant reactive species, contributing 80.9% and 54.0% of IBP removal in EP-ACF and EP-GF systems, respectively. The roles of adsorption in EP-ACF and direct electron transfer in EP-GF cannot be ignored. Due to the differences in mechanism, EP-GF and EP-ACF systems were suitable for the removal of O⋅H-resistant ROCs (e.g., oxalic acid and pyruvic acid) and non-O⋅H-resistant ROCs (e.g., IBP and nitrobenzene), respectively. Both systems had excellent stability relying on the introduction of oxygen functional groups on the anode, and their electrolysis energy consumption was significantly lower than that of EP-Pt system. The three degradation pathways of IBP were proposed, and the toxicity of intermediates were evaluated. In general, carbon anodes have a good application prospect in the removal of ROCs in EP systems.