Actual Wastewater Research Articles

Bibliometric analysis of electrochemical disinfection: current status and development trend from 2002 to 2022.

The removal of waterborne pathogens from water is critical in preventing the spread of waterborne diseases. Electrochemical methods have been extensively researched and implemented for disinfection, primarily owing to their simplicity, efficiency, and eco-friendliness. Thus, it is essential to conduct a review about the research progress and hotspots on this promising technique. In this paper, we provided a comprehensive bibliometric analysis to systematically study and analyze the current status, hotspots, and trends in electrochemical disinfection research from 2002 to 2022. This study analyzed literature related to electrochemical disinfection or electrochemical sterilization published in the Web of Science database from 2002 to 2022 using CiteSpace and Biblioshiny R language software packages. The analysis focused on the visualization and assessment of annual publication volume, discipline and journal distribution, collaborative networks, highly cited papers, and keywords to systematically understand the current status and trends of electrochemical disinfection. The results showed that between 2002 and 2022, 1171 publications related to electrochemical disinfection were published, with an exponential increase in the cumulative number of publications (y=17.518e0.2147x, R2= 0.9788). The publications covered 76 disciplines with many articles published in high-impact journals. However, the research power was characterized by a large number of scattered research efforts and insufficient cooperation, indicating the need for further innovative collaboration. The citation analysis and keyword analysis suggest that future development in this field may focus on optimizing electrode materials, investigating the disinfection performance of ·OH based systems, optimizing conditions for actual wastewater treatment, and reducing energy consumption to promote practical applications.

Excellent treatment effect of actual wastewater from a pesticide plant using electro-Fenton process catalyzed by natural pyrite

The experiment used natural pyrite as catalyst for electro-Fenton process to treat actual wastewater containing high concentrations of chlorine salts from a pesticide factory in Guangdong province, China. It revealed that under the optimized conditions of initial pH of 3, electrode spacing of 4 cm, and current density of 40 mA/cm2, excellent treatment effect was achieved using 3 g/L pyrite as catalyst with graphite cathode and Ti/RuO2-IrO2-SnO2 anode after a duration of 3 h. Specifically, the removal efficiencies of chemical oxygen demand (COD), absorbance at 478 nm (I478), ammonia nitrogen (AN) and total nitrogen (TN) reached 99.1 %, 99.8 %, 98.9 % and 46.0 % respectively, and instantaneous current efficiency (ICE) at 3 h and energy consumption (EC) were 48.16 % and 97 kWh/kgCOD. Pyrite exhibited good reusability, mainly due to its proper dissolution capacity to renew surface active sites. It was speculated that the nitrogen removal of pesticide wastewater might mainly owe to the oxidation of NH4+ by chlorine/hypochlorite which were based on anode discharge reaction of contained Cl−. The electro-Fenton process catalyzed by natural pyrite showed good potential for efficiently treating the actual pesticide processing plant wastewater with high contents of chlorine salts.

Enhanced recovery of phosphorus from hypophosphite-laden wastewater via field-induced electro-Fenton coupled with anodic oxidation

Electrochemical recovered ferric phosphate (FePO4) precipitates from hypophosphite-laden wastewater were shown to be an efficient method for phosphorus (P) recovery. However, the influence of chloride ions (Cl−) coexisting commonly in wastewater is not known for this treatment. Herein, a field-induced electro-Fenton coupled with anodic oxidation electrochemical system consisting of a Ti-RuO2 anode, an Fe inductive electrode and an activated carbon fiber (ACF) cathode, namely Ti-RuO2/Fe/ACF(NaCl) system, was established to recover phosphorus (P) as FePO4 from hypophosphite-laden wastewater in the presence of Cl−. This system enabled a hypophosphite (H2PO2−, 1.0 mM) removal ratio of ~100% and all P was recovered within 30 min at 5.0 V under the initial solution pH of 3.0. The Faradaic efficiency and energy consumption of P recovery achieved the maximum value (~94%) and the lowest value (~16 kW h kg−1 P), respectively. Reactive oxygen species including 1O2, FeIVO2+, •O2− and •OH contribute to convert H2PO2− to PO43−, which immediately formed FePO4 with the generated Fe3+ at the optimized conditions. Therein, the contribution of non-radical 1O2 was very considerable. This system exhibited good stability. The efficiency and cost for treatment of actual hypophosphite-laden wastewater were addressed to check its applicability for P recovery.

Vacancy-Rich CoSx@LDH@Co-NC Catalytic Membrane for Antibiotic Degradation with Mechanistic Insights.

Improving the wettability of carbon-based catalysts and overcoming the rate-limiting step of the Mn+1/Mn+ cycle are effective strategies for activating peroxymonosulfate (PMS). In this study, the coupling of Co-NC, layered double hydroxide (LDH), and CoSx heterostructure (CoSx@LDH@Co-NC) was constructed to completely degrade ofloxacin (OFX) within 10 min via PMS activation. The reaction rate of 1.07 min-1 is about 1-2 orders of magnitude higher than other catalysts. The interfacial effect of confined Co-NC and layered double hydroxide (LDH) not only enhanced the wettability of catalysts but also increased the vacancy concentration; it facilitated easier contact with the interface reactive oxygen species (ROS). Simultaneously, reduced sulfur species (CoSx) accelerated the Co3+/Co2+ cycle, acquiring long-term catalytic activity. The catalytic mechanism revealed that the synergistic effect of hydroxyl groups and reduced sulfur species promoted the formation of 1O2, with a longer lifespan and a longer migration distance, and resisted the influence of nontarget background substances. Moreover, considering the convenience of practical application, the CoSx@LDH@Co-NC-based catalytic membrane was prepared, which had zero discharge of OFX and no decay in continuous operation for 5.0 h. The activity of the catalytic membrane was also verified in actual wastewater. Consequently, this work not only provides a novel strategy for designing excellent catalysts but also is applicable to practical organic wastewater treatment.

Metal-encapsulated nitrogen-doped carbon nanotube arrays electrode for enhancing sulfion oxidation reaction and hydrogen evolution reaction by regulating of intermediate adsorption

For treatment of sulfion-containing wastewater, coupling the electrochemical sulfion oxidation reaction (SOR) with hydrogen evolution reaction (HER) can be an ideal way for sulfur and H2 resources recovery. Herein, we synthesize a metal-modified carbon nanotube arrays electrode (Co@NCNTs/CC) for SOR and HER. This electrode has excellent performance for SOR and HER attributed to the unique array structure. It can achieve 99.36 mA/cm2 at 0.6 V for SOR, and 10 mA/cm2 at 0.067 V for HER. Density functional theory calculations verify that metal modification is able to regulate the electronic structure of carbon nanotube, which is able to optimize the adsorption of intermediates. Employed Co@NCNTs/CC as bifunctional electrodes to establish a hybrid electrolytic cell can reduce about 67% of energy consumption compared with the traditional water splitting electrolytic cell. Finally, the hybrid electrolytic cell is used to treat actual sulfion-containing wastewater, achieving the sulfur yield of 30 mg h−1 cm−2 and the hydrogen production of 0.64 mL/min.

Cobalt(II) mediated calcium sulfite activation for efficient oxidative decontamination in waters: Performance, kinetics and mechanism

To overcome the drawback that excess SO32− from soluble Na2SO3 captures the generated reactive intermediates in sulfite (S(IV))-based advanced oxidation processes (AOP), CaSO3 of the ability to slowly release SO32− is selected as an alternative S(IV) source to establish an enduring S(IV)-based AOP with Co(II). Herein, the Co(II)/CaSO3 process triggers a much better ofloxacin (OFL) degradation than the Co(II)/Na2SO3 process (degradation rate constant: 12.1 > 3.18 mM−1 min−1). The mechanism investigation corroborates that the Co(II) mediated CaSO3 activation follows a Fenton-like process (complexation followed by intramolecular electron transfer). Apart from the conventional sulfate radical (SO4•−), Co(IV) species and singlet oxygen (1O2) are also certifiably involved in Co(II)/CaSO3 process, and their role and formation mechanisms are elucidated comprehensively. Further, the proposed Co(II)/CaSO3 process exhibits an excellent tolerance to complex water matrices (e.g., background ions and humic acid), suggesting its practical application potential for various contaminants abatement in actual wastewater.

Investigation into the electrochemical advanced oxidation of p-arsanilic acid: Peculiar role of electrolytes and unexpected formation of coupling byproducts

Although banned in some countries, p-arsanilic acid (ASA) is still widely used as feed additive in poultry production. As a result, ASA is usually released into the aquatic environment without any treatments. Although ASA exhibits low toxicity, it can be transformed into highly toxic aromatic amines and inorganic arsenic species (As (V) as H2AsO4− and HAsO42−) under natural environmental conditions. Hence, it is necessary to develop efficient technologies for its removal or degradation. In this contribution, electrochemical advanced oxidation technology with boron-doped diamond (BDD) had been initially used to degrade ASA pollutants. A five-level central composite rotatable design (CCRD) was implemented to optimize the various influencing factors involved, among applied current density, NaCl concentration, Na2SO4 concentration and NaHCO3 concentration on the oxidation efficiency; the latter was assessed in terms of ASA degradation percentage. The results obtained highlighted the unique and important roles of electrolytes during the electrolytic oxidations. Meanwhile, the major degradation byproducts detected were also strongly dependent on the electrolyte adopted. In particular, several oligomer byproducts with novel structures were initially identified in BDD-treated ASA solutions. Two different electrochemical transformation pathways of ASA on BDD anode were thus proposed. This study demonstrated the effectiveness of BDD technology in the degradation of ASA, as well as the potential minor risk of its application in actual ASA wastewater treatment.

Biomimetic hydrophilic CuO-nanocluster/nanofibrous thin-film skeleton/hydrophilic CuO-nanocluster architecture membrane for efficient and stable solar water evaporation

Developing exquisitely structured light-absorbing materials could be a feasible approach to enhance solar evaporation performance. Herein, a CuO-nanocluster/PVDF-HFP nanofibrous thin-film skeleton/CuO-nanocluster (CPC) architecture membrane was developed via electrospinning, heating, and hydrothermal techniques. The CPC membrane architecture is similar to the triple-layer mesophyll/vein/mesophyll in a natural leaf, whereby mesophyll performs photosynthesis for plant growth and the vein acts as a support skeleton. Similarly, CPC mimicking a leaf structure possesses: (1) upper and lower hydrophilic CuO-nanoclusters to absorb sunlight, promote water supply, and prevent salt crystallization during the evaporation process; and (2) a middle nanofibrous thin-film membrane that acts as a supportive layer. The resulting CPC membrane exhibited an evaporation rate of 1.21 kg m−2 h−1 and 1.06 kg m−2 h−1 for 3.5 wt% saline water and actual industry dye wastewater, respectively. Meanwhile, the CPC membrane was applied in the cycle, continuous, and outdoor evaporation tests. In addition, the CPC membrane displayed impressive mechanical strength and flexibility, making it suitable for the long-term use in practical applications. These findings demonstrate the excellent performance of the CPC membrane for solar water evaporation and should inspire further research on developing dedicated architecture membranes for use in fields such as catalysis, sensing, energy, and other applications.

Fabrication of Bi/BiOCOOH/PVDF with improved photocatalytic activity for the degradation of ciprofloxacin

The development of a low-cost and recyclable method for wastewater treatment has been a major challenge. Polyvinylidene fluoride (PVDF) membranes have received considerable attention owing to their excellent mechanical strength, unique antioxidant properties, and low cost. In this study, Bi/BiOCOOH/PVDF composite membrane materials were prepared using a simple two-step solvent thermal method and phase conversion method. The results showed that under the synergistic action of adsorption and photocatalysis, the photocatalytic degradation efficiency of Bi/BiOCOOH composite material and Bi/BiOCOOH/PVDF composite membrane material for ciprofloxacin (CIP) was much higher than that of BiOCOOH. The introduction of PVDF acted as a carrier, improved the adsorption of the catalytic material to CIP, and facilitated the effective collision of the photocatalytic active site and CIP. The experimental results and theoretical calculations confirmed that the combination of Bi and BiOCOOH effectively improved the light absorption capacity and photocatalytic performance. The reproducibility test revealed that the small amount of new composite catalyst for Bi/BiOCOOH/PVDF as a carrier was lost and that the Bi/BiOCOOH/PVDF catalyst still had high catalytic activity. In addition, the influence of water matrix factors, such as pH and anion, on the photocatalytic degradation experiment was investigated, which would provide some reference for the actual wastewater treatment of the composite catalyst. This study demonstrates a photocatalytic activation mechanism between metals and semiconductors and provides some basis for constructing catalysts for the synergistic and effective treatment of water pollution through a combined adsorption and photocatalysis process.

Chromium Disarmament from Veritable Tanneries Sewer Water Utilizing Carbonic Rice Straw as a Sorbent: Optimization and Carbonic Rice Straw Characteristics

This exploration focuses on the removal of chromium from actual tannery wastewater, collected from the HARBY TANNERY factory in Rubiki (Badr City), using an economical sorbent made from activated carbon derived from rice straw (CRS). The CRS sorbent is activated using H3PO4. The experiment aims to assess the impact of various parameters, including chromium initial concentration, sorbent dosage, treatment time, agitation velocity (rpm), sorbent particle size, and solution pH, on chromium removal from tannery wastewater. Structural, morphological, and electronic distinctive of raw and treated CRS, as well as carbonized CRS, were analyzed using FTIR, SEM, and TEM techniques. XRF analysis was conducted to investigate the chemical elemental composition of carbonized CRS before and after sorption. Zeta potential measurement was performed to assess the electrical charges of particles present in a suspension. The adsorption data was tested for both Langmuir and Freundlich adsorption isotherms, and most of the factors suggested that it follows the Langmuir adsorption isotherm with an R2 value of 99.67%. Additionally, adsorption kinetics were performed to identify the reaction order, which exhibited that sorption pursued pseudo-second-order kinetics with a rate constant (k) of 0.0658 g/mg g/min, a high correlation factor (R2) of 99.76%, and an estimated equilibrium chromium ion adsorption capacity (qe) of 1.597 mg/g, which closely matched the experimental data (1.4835 mg/g). The improved surface morphology and increased surface area of CRS resulted in approximately 98.9% chromium removal. Mechanism studies confirmed that intraparticle diffusion is not the sole rate-controlling step, and Boyd’s model demonstrated that film diffusion limited the rate of chromium adsorption. The desorption of chromium from the carbonized rice straw surface could be achieved by up to 96.4% of the sorbed amount by raising the solution pH to 10, indicating the potential reusability of carbonized rice straw for additional adsorption cycles. Finally, a statistical regression analysis and least square multivariate analysis were used to establish a correlation for predicting efficiency, yielding an R2 value of 97.54%.

The synergistic degradation of pollutants in water by photocatalysis and PMS activation.

In recent years, the synergistic degradation of water pollutants through advanced oxidation technology has emerged as a prominent research area due to its integration of various advanced oxidation technologies. The combined utilization of peroxymonosulfate (PMS) activation technology and photocatalysis demonstrates mild and nontoxic characteristics, enabling the degradation of water pollutants across a wide pH range. Moreover, this approach reduces the efficiency of electron hole recombination, broadens the catalyst's light response range, facilitates electron transfer of PMS, and ultimately improves its photocatalytic performance. The paper reviews the current research status of photocatalytic technology and PMS activation technology, respectively, while highlighting the advancements achieved through the integration of photocatalytic synergetic PMS activation technology for water pollutant degradation. Furthermore, this review delves into the mechanisms involving both free radicals and nonradicals in the reaction process and presents a promising prospect for future development in water treatment technology. PRACTITIONER POINTS: Degradation of water pollutants by photocatalysis and PMS synergistic action has emerged. Synergism can enhance the generation of free radicals. This technology can provide theoretical support for actual wastewater treatment.

Selective capture of palladium from acid wastewater by thiazole-modified activated carbon: Performance and mechanism

As a kind of scarce metal, palladium is widely used in many chemical industries. It essential to recover palladium from secondary resources, especially acidic media, owing to high content of palladium in secondary wastes and widespread extraction of palladium via strong acids. Chemically modified carbon materials not only have the advantage of activated carbon but also achieve the precise removal of specific pollutants, which is a kind of adsorption material with broad application prospects. In this direction, we report a solid carbon material named AT-C, which is obtained by one-step synthesis of 2-aminothiazoles grafted to the carbon surface by amidation. The present adsorbent delivers a high palladium adsorption capacity of 178.9 mg g−1, and desirable thermal and chemical stability. The uniform presence of abundant sulfur atoms and CO in the porous network enables AT-C to achieve selective absorption and rapid adsorption kinetics of Pd2+ in the complex water mixture containing many competing ions in the acidic pH range. For the strongly acidic leachates of catalysts, AT-C exhibits outstanding stability in cyclic experiments. Meanwhile, the fixed-bed column test indicates that 1076 bed volumes of the feeding streams can be effectively treated. In addition, AT-C exhibits superior adsorption selectivity, and the recovery efficiency of Pd2+ in actual industrial wastewater is 96.6%. This work realizes an efficient, rapid, and selective removal of palladium under acidic conditions, and provides a reference for complex industrial water treatment and resource recovery of precious metals.

Reactor performance of static magnetic field membrane bioreactor for treating actual high-salt textile dyeing wastewater and possible mechanism on magnetically enhanced membrane fouling control

Performance of the static magnetic field membrane bioreactor (SMFMBR) for treating actual high-salt textile dyeing wastewater was evaluated. Membrane fouling behavior and possible mechanisms were investigated using multiple methods including chemical composition analysis, microbial community analysis, and four-dimensional label-free quantification metaproteomic analysis. The results showed that three SMFMBRs equipped with the SMFs of 97.2 mT (1#), 202.3 mT (2#) and 303.4 mT (3#) possessed higher removal efficiency of color, chemical oxygen demand (COD) and acute toxicity, as well as higher activity of key enzymes than the conventional MBR (0#). Treatment efficiency of 3# SMFMBR was the highest among all the four groups. Potentially effective bacterial and fungal species were selectively enriched in the suspended sludge of three SMFMBRs according to the results of both high-throughput sequencing and quantitative real-time polymerase chain reaction (QRT-PCR). Membrane fouling rate of 3# SMFMBR was the lowest among all the groups, followed by that of 2#, 0# and 1# reactors. SMF of higher intensity (in 2# and 3# SMFMBRs) mitigated membrane fouling by inhibiting the production of microbial products (mainly consisting of proteins) and the growth of potential fouling-causing microbes on the membrane surface. By contrast, SMF of lower intensity (in 1# SMFMBR) aggravated membrane fouling by improving the yield of fouling-causing microbial products and the growth of biofilm on the membrane surface. Furthermore, the down-regulated porin and the up-regulated Ca2+-binding protein in biocake EPS were also responsible for the mitigation of membrane fouling in 3# SMFMBR.

Enhanced removal capacities and mechanisms of Mn/Fe-loaded biochar composites functionalized with chitosan Schiff-base or hydroxyl toward Pb(II) and Cd(II) from aqueous solutions

The efficient capture of heavy metal ions from actual wastewater is a global challenge. To enhance Pb(II) and Cd(II) removal, novel biochar composites (MF@CBC, MF-S@CBC and MF-OH@CBC) were successfully fabricated by loading magnetic Mn-Fe binary oxides and functionalizing chitosan Schiff-base or hydroxyl on biochar in the study. The maximum adsorption capacities of MF-OH@CBC and MF-S@CBC toward Pb(II)/Cd(II) were 196.69/187.29 mg/g and 161.61/153.69 mg/g (pH = 5.0, adsorbent dosage = 0.5 g/L), which were 2.09/3.05 and 1.54/2.33 times higher than corn cob biochar (CBC), respectively. The adsorption processes were conformed to Langmuir isothermal model and pseudo second order model. The numerous functional groups presented on MF-OH@CBC resulting from loading Mn-Fe nanoparticle and hydroxylation might be the main reason for dominating adsorption of Pb(II)/Cd(II) by complex interaction (contribution rate (CR) = 45.66%/43.12%). And also, the negative charge on MF-OH@CBC might be another reason for enhancing adsorption of Pb(II)/Cd(II) by electrostatic interaction (CR = 23.11%/22.45%). Besides, ion exchange (CR = 17.95%/19.33%) and physical adsorption (CR = 13.28%/15.10%) could also contributed to Pb(II)/Cd(II) removal. In addition, MF-OH@CBC displayed favorable recycling ability and its adsorption capacity retained over 80% after five cycles. It also exhibited anti-interfering ability, the adsorption capacity for Pb(II)/Cd(II) in actual sewage was 85.27%/80.47%, respectively. The results indicated that MF-OH@CBC possessed good potential for eliminating Pb(II) and Cd(II) from the complex aqueous environment.

Nano-CuOx for ciprofloxacin effective removal via wet peroxide oxidation catalysis and its practical application in wastewater

Using Cu(NO3)2·3H2O as active material and citric acid (CA) as complexing agent, heterogeneous catalyst nano-CuOx was prepared by sol-gel method. The catalytic wet peroxide oxidation (CWPO) reaction system was established accordingly. The system was used to treat ciprofloxacin (CIP) in simulated wastewater and real wastewater. The effects of the molar ratio of metal salt to CA, calcination temperature, H2O2 dosage, reaction temperature, and catalyst dosage on the physicochemical structure and the properties of CWPO were investigated. The results showed that when the molar ratio of CA to metal salt (Cu(NO3)2·3H2O) was 1.8, the calcination temperature was 500 °C, the concentration of H2O2 was 10 mmol · L–1, the reaction temperature was 95 °C, and the dosage of catalyst was 1 g · L–1, CWPO system has the best degradation effect on CIP. At thses optical conditions, the removal rate reached 86.8%, chemical oxygen demand (COD) removal rate reached 54.9%, and the recycling rate of the catalyst was very good. The refractory organics in actual pharmaceutical wastewater could be oxidized by this system as well, and the COD removal rate reaches 47%. The degradation mechanism of CIP showed that the main functions of the CWPO system were ·O2– and ·OH radicals. The possible degradation pathways were determined by ion chromatography to be intermediate products generated from piperazine ring cleavage, defluorination, decarboxylation, and quinoline hydroxylation of CIP. The catalyzing mechanism was investigated in detail; some useful information was obtained in this work.

Efficient degradation of refractory pollutant boosted by combining heterogeneous electro-Fenton on the hydrophobic modified gas diffusion electrode with anodic oxidation

To boost refractory pollutant removal over a broad pH range, we here proposed an integrated electrocatalytic process combining electrochemical anodic oxidation (AO) with cathodic electro-Fenton (EF) based on a hydrophobic modified gas diffusion electrode and heterogeneous Fenton catalyst of FeOCl. Total organic carbon (TOC) removal of refractory levofloxacin by EF + AO process was 85% in 120 min under the applied potential of −0.6 V and pH ∼6.7, obviously higher than that of only AO (22%) or EF (62%) process. Significantly, EF+AO process was demonstrated to be efficient and stable for actual wastewater treatment that chemical oxygen demand (COD) value of refinery wastewater after EF + AO treatment was steadily met the discharge standard (GB 18918–2002) for sewage treatment plants in China (I-A: COD < 50 mg/L) during 100 h of consecutive runs. Our results provide new insights into developing an energy-efficient electrocatalytic technology for enhancing refractory pollutant removal.

In situ grown, super-hydrophilic and multifunctional hydroxyapatite composite membrane for oil–water separation

In this paper, a method of growing SiO2 on hydroxyapatite in situ and depositing it into polydopamine-modified MCEM membrane was reported to prepare super-hydrophilic underwater super-oleophobic coatings. The results showed that the hydrophilic properties of SiO2, the hydroxy-rich structure of hydroxyapatite and the synergistic action of polydopamine made the membrane have excellent hydrophilicity. The modified HAP@SiO2/PDA coating membrane not only had excellent mechanical properties, but also had good oil and water selectivity. At the same time, the membrane separation flux of light oil can reach 3000 L/(m2·h), and the oil discharge rate of heavy oil can reach 98.95%. More importantly, the membrane can remove 90.90% of the actual oilfield wastewater. As a result, HAP@SiO2/PDA coatings can effectively treat a wide range of oily wastewater and demonstrate attractive separation capabilities.

Green fabrication and photoactivity of novel heteroatom modified metal heaxcyanocobaltate nanocomposites for efficient removal of organic pollutants from wastewater

Herein, structural design of nitrogen-doped metal hexacyanocobalate nanocomposite (N-MHCC; M = Zn, Ni, Fe) have been synthesized via facile precipitation and green synthesis methodology—aqueous leaves extract of A. marmelos used as a natural surfactant. The unique cubical morphology (particle size less than 100 nm) of nanocomposite and the binding energy peak of N at 399 eV confirmed the successful doping of nitrogen in MHCC. The green synthesized N-MHCC treated with toxic Endosulfan (ES) pesticide and phenazinium Safranin (SF) dye under various reaction conditions (pollutant conc: 10–30 mgL-1; catalytic dosage: 20–40 mg; pH: 3–10, irradiation source: artificial bulb, dark, sunlight). N–ZnHCC showed maximum degradation (ES-90%: SF-95%) followed by Ni–NiHCC (ES-82%; SF-87%) and N–FeHCC (ES- 75%; SF-79%) under sunlight irradiation due to negative zeta potential (−20.0 mV), higher surface area (29.1 m2g-1) and lower band gap (1.7 eV). First-order kinetics followed by initial Langmuir adsorption constituted the degradation process. The presence of different radical quenchers (t-BuOH, p-BZQ, Na2EDTA) concluded that hydroxyl radical plays a significant role in the degradation of toxic ES and SF. Green fabricated N-MHCC also showed excellent efficiency for the degradation of ES and SF pollutant in actual wastewater sample. Nanocomposite demonstrated remarkable sustainability and cost-effectiveness by remaining effective for up to eight cycles without experiencing any appreciable activity reduction. Overall, due to its favourable surface features, N-MHCC nanocomposite made in green is a unique and potential photocatalyst for industrial applications.

Nano zero-valent iron-based fiber electrode for efficient electro-Fenton treatment of pharmaceutical wastewater: Mechanism of degradation and sterilization

In this study, a novel metal–organic framework (MOF) derived fiber electrode (NZVIF-800) was successfully fabricated by a novel electrostatic spinning and pyrolysis procedure. The NZVIF-800 electrode exhibited great catalytic activity in a heterogeneous electro-Fenton (EF) system for organic degradation, in which the secnidazole (SCZ) was completely degraded within 60 min with excellent stability (no significant change after eight cycles). Importantly, the NZVIF-800 electrode was also highly effective for decontaminating actual pharmaceutical wastewater, in which the TOC and COD removal reached 38% and 47%, respectively, after 4 h EF reaction. Based on experimental analysis, microstructure characterization, and theoretical calculations, the detailed reaction mechanism of the NZVIF-800 electrode was revealed. The impressive EF performance was mainly attributed to the in situ generation of active nano-zero-valent iron (NZVI) derived from the MOF pyrolysis and the confinement effect of the encased carbon layer that could effectively inhibit the loss and inactivation of Fe active sites. The degradation pathways of organic pollutants in simulated and real wastewater were proposed in detail. Significantly, the EF system with NZVIF-800 electrode exhibited strong sterilization ability for the wastewater matrix as evidenced by the colony condition, OD600 values, and Illumina MiSeq sequencing platform analysis (up to 95% sterilization efficiency within 4 h), expanding its application scope for actual wastewater treatment.

Biowaste derived UV–Visible-NIR active Z-scheme CaO/MoS2 photocatalyst as a low-cost, waste-to-resource strategy for rapid wastewater treatment

There is a need for industries to adopt greener strategies to minimise the environmental impact and overuse of natural resources. In the light of alarming environmental conditions, there is an expanding and progressing centre around the concept of waste to resource strategy. With this inspiration, a low-cost marine biowaste-based CaO/MoS2 photocatalyst synthesized by ball milling is proposed with a viable green route for water remediation. The mass ratio of CaO and MoS2 were optimized for the photocatalytic reduction of cationic methylene blue (MB) as a probe dye and an actual industrial dye wastewater. It was found that 45CaO/55MoS2 (45-CaMo) outperformed all the proportions including the conventionally popular TiO2. 70% of MB got discoloured in 10 min of exposure to natural sunlight following Langmuir-Hinshelwood model with a rate constant of 0.064 min−1 and exhibiting good photo-stability. The morphology and crystallinity were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). UV–Visible-NIR spectroscopy and calculations reveal the activity of the synthesized photocatalyst in UV, visible and IR regions with a direct Z-scheme mechanism as its probable charge modulation technique. This work offers new perspectives and directions for future research using waste-derived resources and renewable energy.