Removal Of Organic Contaminants Research Articles

Synthesis and Application of Innovative and Environmentally Friendly Photocatalysts: A Review

Modern society faces two major challenges: removing pollutants from water and producing energy from renewable sources. To do this, science proposes innovative, low-cost, and environmentally friendly methods. The heterogeneous photocatalysis process fits perfectly in this scenario. In fact, with photocatalysis, it is possible both to mineralize contaminants that are not easily biodegradable and to produce hydrogen from the water splitting reaction or from the conversion of organic substances present in water. However, the main challenge in the field of heterogeneous photocatalysis is to produce low-cost and efficient photocatalysts active under visible light or sunlight. The objective of this review is to compare the new proposals for the synthesis of innovative photocatalysts that reflect the requirements of green chemistry, applied both in the removal of organic contaminants and in hydrogen production. From this comparison, we want to bring out the strengths and weaknesses of the proposals in the literature, but above all, new ideas to improve the efficiency of heterogeneous photocatalysis guaranteeing the principles of environmental and economic sustainability.

Simultaneous removal of organic inorganic composite contaminants by in situ double modified biochar: Performance and mechanisms

BackgroundIn this study, double modified biochar was prepared to remove organic matter and heavy metals at the same time. It has high removal efficiency for organic matter even in actual irrigation water. MethodsTobacco stem was used as carbon-based carrier, modified with polyacrylic acid (PAA) rich in oxygen functional groups (OFGs) and transition metals (iron and cobalt) with excellent catalytic activity. After mixing them evenly, the in-situ double modified biochar (BCPAA@CFO) of OFGs and CoFe2O4 (CFO) was obtained by one-step hydrothermal carbonization (HTC). Significant findingsBCPAA@CFO in QNC-Pb2+composite system, CFO can quickly activate peroxymonosulfate (PMS), and the degradation efficiency of quinclorac (QNC) is as high as 80.7%. Free radical quenching experiments and electron paramagnetic resonance (EPR) analysis indicated that SO4·−, ·OH, ·O2− and 1O2 were the main active species involved in the degradation of QNC. At the same time, the rich OFGs make the adsorption efficiency of Pb2+reach 73.2% within 4 h. FT-IR results further confirmed that the dominant role of adsorption should be OFGs. In general, this in-situ double modified BCPAA@CFO obtained by one pot HTC is a promising purifying agent for mixed pollutants.

Effects of pre-treatments on the filtration performance of ultra-low pressure gravity-driven membrane in treating the secondary effluent: Flux stabilization and removal improvement

Gravity-driven membrane (GDM) filtration is a promising technology for decentralized water and wastewater treatment due to its negligible energy consumption and low maintenance. This study investigated the flux development and permeate quality of the GDM process in treating the secondary effluent, as well as the influences of two practical pre-treatments, including GAC filter and microfiltration (MF), on its filtration performance. The results indicated that the GAC filter could significantly enhance the removal of organic contaminants (i.e., DOC, UV254, and fluorescent substances), with an average removal of 70 % for DOC and 80 % for UV254, respectively. Meanwhile, GAC/GDM systems exhibited a superior removal performance of manganese and sulfamethoxazole (SMX) for more than 95 % and 80 %, respectively. Furthermore, the optimized mixing ratio between GAC permeates and secondary effluent was 7:3 (GAC7:3) to reach a flux level close to the GDM control and achieve a superior permeate water quality than the other processes. The flux of GDM control could stabilize at the level of 5.47 ± 0.71 L m−2h−1 during long-term filtration. Unexpectedly, limited flux improvements were observed with the pre-treatments, and the stable flux of GAC/GDM and MF/GDM was close to or slightly lower than the GDM control. In GDM control, a rough, heterogeneous, and porous biocake layer was observed on the membrane surface. By contrast, the cake layer structures in the GDM system coupled with pre-treatments appeared denser, compact, and homogeneous, resulting in relatively lower stable flux relative to the GDM control. The economic assessment indicated that the optimized process of GAC7:3 showed a significant cost advantage in the small and medium-scale water reuse scenarios. These findings were beneficial to develop new energy-saving membrane-based technology for the reclamation of wastewater.

Improving the ozone-activated peroxymonosulfate process for removal of trace organic contaminants in real waters through implementation of an optimized sequential ozone dosing strategy

The ozone-activated peroxymonosulfate process (O3/PMS) has received increasing attention for the removal of trace organic contaminants (e.g. pesticides and pharmaceuticals) from water bodies. However, the ozone dosing strategy has not yet been properly investigated, especially in real water matrices. Typically, one-step dosing is applied in literature. Nevertheless, optimal dosing is an important step for improving the process. This study investigates the effect of sequential ozone dosing on the PMS activation, atrazine (ATZ) removal, residual ozone concentration and radical exposure, and compares the results to those of a one-step ozone dosing approach. Experiments were performed in three water matrices with a different (in)organic content, i.e. secondary effluent, surface water and groundwater. In all matrices, the highest PMS activation was reached when applying three sequential ozone doses (3 × 5 mg O3/L). This resulted in a 3 times higher ATZ removal efficiency (up to 46 %) in secondary effluent compared to that obtained with a one-step ozone dosing (15 mg O3/L). In surface water and groundwater, similar ATZ removal (>90 %) was observed among the different ozone dosing strategies. However, the sulfate radical (SO4●−) exposure increased after each ozone addition. After three ozone additions of 5 mg/L, SO4●− contributed for 9 %, 26 % and 54 % to ATZ removal in respectively secondary effluent, surface water and groundwater. This high SO4●− contribution compared to ●OH contribution is an advantage as the selectivity of SO4●− gives rise to less radical scavenging by bulk organic matter and thus increases the (cost-)effectiveness of the O3/PMS process.

Visible-Light-Driven Photocatalysts for Self-Cleaning Transparent Surfaces.

Highly transparent photocatalytic self-cleaning surfaces capable of harvesting near-visible (365-430 nm) photons were synthesized and characterized. This helps to address a current research gap in self-cleaning surfaces, in which photocatalytic coatings that exhibit activity at wavelengths longer than ultraviolet (UV) generally have poor optical transparency, because of broadband scattering and the attenuation of visible light. In this work, the wavelength-dependent photocatalytic activity of Pt-modified TiO2 (Pt-TiO2) particles was characterized, which exhibited activity for wavelengths up to 430 nm. Pt-TiO2 nanoparticles were embedded in a mesoporous SiO2 sol-gel matrix, forming a superhydrophilic surface that allowed for water adsorption and formation of reactive oxide species upon illumination, resulting in the removal of organic surface contaminants. These self-cleaning surfaces only interact strongly with near-visible light (∼365-430 nm), as characterized by photocatalytic self-cleaning tests. Broadband visible transparency was preserved by generating a morphology composed of small clusters of Pt-TiO2 surrounded by a matrix of SiO2, which limited diffuse visible light scattering and attenuation. The wavelength-dependent self-cleaning rate by the films was quantified using stearic acid degradation under both monochromatic and AM1.5G spectral illumination. By varying the film morphology, the average transmittance relative to bare glass can be tuned from ∼93%-99%, and the self-cleaning rate can be adjusted by more than an order of magnitude. Overall, the ability to utilize photocatalysts with tunable visible light activity, while maintaining broadband transparency, can enable the use of photocatalytic self-cleaning surfaces for applications where UV illumination is limited, such as touchscreen displays.

Highly efficient removal of organic contaminants and hydroxylamine hydrochloride enhancement effect based on magnetic iron/nitrogen doped carbon nanolayer

Developing highly effective and environmental friendliness Fe-based catalysts have attracted increasing attention. Herein, novel nitrogen-doped carbon nanolayer with Fe0/Fe3C nano-particles (Fe@NCL-900) were innovatively fabricated by a simple solvent-free strategy, pyrolyzed the mixture of 4,6-dihydroxypyrimidine and ferric chloride hexahydrate under 900 ℃. In the presence of peroxymonosulface (PMS), Fe@NCL-900 could remove almost 100% Carbamazepine in 6 min with an amazing apparent first-order constant (kobs) as high as 0.733 min−1, about 72 and even 88 times higher than that of the commercial zero-valent iron and the traditional Fenton system, respectively, which was mainly ascribed to the synergistic effect of high graphite carbon and excellent reducing ability of Fe0. Moreover, high valent iron species (Fe (IV)) and four types of reactive oxygen species (ROS) including hydroxyl radical (•OH), sulfate radical (SO4•-), singlet oxygen (1O2), superoxide radical (O2•-) were detected to play a key role in Carbamazepine removal by electron paramagnetic resonance (EPR) and the radical quenching experiments. Interestingly, it was observed that the addition of hydroxylamine hydrochloride could effectively improve the production of more ROS and the first-order constant was enhanced by 7.6 times (5.593 min−1), completely different from the previous reports that hydroxylamine hydrochloride in high concentrations would inhibit the removal rate. Moreover, the magnetically separable catalyst possessed a wide pH range (2.0–10.0) and superior reusability. This study provides novel insights for manufacturing a promising Fe-based nitrogen-doped catalyst in practical wastewater treatment.

Energy-Efficient H2O2 Electro-production Based on an Integrated Natural Air-Diffusion Cathode and Its Application

Given the low oxygen mass transfer rate and high aeration energy consumption, the traditional two-electron oxygen reduction reaction (ORR) is restricted. In this study, the integrated natural air diffusion cathode (INAC) and a reactor configuration with the horizontal scale facing to air (FTA) demonstrated highly selective H2O2 production for the removal of organic contaminants. Simply synthesized by shaping the mixture of carbon black and polytetrafluoroethylene, the INAC exhibited not only massive pores in all directions for sufficient mass transfer but also the integrated configuration for low charge transfer resistance. Based on the oxygen mass transfer models, for the ORR reaction kinetics, the interface oxygen concentration index was higher than 40, contributing to the high current efficiency of H2O2 production (>90%). The oxygen diffusion model can provide the quantitative description of H2O2 synthesis for porous electrode optimized design. Combining the INAC with the reactor configuration with the FTA mode for free additional O2/air source supply, the electrical efficiency per order was lower than 0.14 kWh m–3, and the removal rate of sulfonamides per unit current could reach 11 mg min–1 A–1, reaching the best reports. This ultraefficient process equipped with the INAC and the FTA mode provides a meaningful practical application prospect for wastewater treatment.

Structural and XPS studies of polyhedral europium doped gadolinium orthovanadate (Eu3+:GdVO4) nanocatalyst for augmented photodegradation against Congo-red

The present work demonstrates structural, valence band mapping (VBM) and photocatalytic activity of Eu3+ doped orthovanadate (GdVO4) nanosystem against an azo-dye, Congo-red. As evident from x-ray diffraction (XRD) studies, the nanosystem synthesized via a solid-state cum sintering route exhibited zircon-type crystal structure with space group I 41/amd. Imaging through transmission electron microscopy (TEM) has revealed polyhedral nanoaggregates, which are of polycrystalline nature. Introduction of Eu3+ into the host GdVO4 was substantiated from the energy dispersive x-ray (EDX) spectra, x-ray photoelectron spectra (XPS) and considering inclusion of dopants to binding energy correspondence in the VBM spectra. In this study, the azo-dye Congo-red has been opted as the target dye for photodegradation. After UV light illumination, Eu3+:GdVO4 nano-catalyst could degrade the organic dye quite effeciently (up to 91.8%), and offering a rate constant nearly doubled as compared with its undoped counterpart. The dopant ions being associated with the new localized states enabling promotion of additional photoexcited carriers taking advantage of the incident UV exposure. Structural, XPS, and optical studies of the rare-earth vanadate nano-systems as well as their photocatalytic activity would provide new insights to resolve existing concerns, viz., removal of organic contaminants, and environmentally harmful dyes and to carry multi-functional scope for industrial relevance. Moreover, such systems may have immense potential for displaying select emission response as well as photocatalysis even though both processes are mediated via opposite effects.

Oxygen hyper stoichiometric trimetallic titanium doped magnesium ferrite: Structural and photocatalytic studies

Oxygen hyper stoichiometric titanium doped magnesium ferrite, Mg 1-x Ti x Fe 2 O 4+δ (x = 0–1.0) nanoparticles (NPs) were synthesized using sol-gel method. XRD analysis revealed a decrease in the lattice parameter from 8.9 to 8.3 Å and confirmed the incorporation of Ti 4+ , a smaller ionic radius dopant. Presence of M-O vibrational bands at tetrahedral and octahedral sites were authenticated by FT-IR analysis. The observed reduction in saturation magnetization values from 23.3 emug −1 to 18.3 emug −1 was ascribed to the doping of non-magnetic Ti 4+ ions in MgFe 2 O 4 NPs. BET studies corroborated the mesoporous nature of the NPs and doped ferrite NPs displayed larger surface area (53.0–73.0 m 2 g -1 ) as compared to pristine ferrite NPs (32.8–39.0 m 2 g -1 ). Optical studies displayed red shift in the absorption edge of the Ti 4+ doped MgFe 2 O 4 NPs in contrast to pristine NPs. Oxygen hyper stoichiometry in the doped ferrite NPs was determined experimentally. Photoluminescence emission spectra exhibited reduction in the emission intensity in case of Ti 4+ doped NPs which supported their higher light capturing potential. Among synthesized doped ferrite NPs Mg 0.5 Ti 0.5 Fe 2 O 4.5 NPs exhibited maximum (98%) photodegradation capacity for rhodamine B. The • O 2 − and • OH were the main reactive species in the photodegradation. The present studies have clearly shown the potential of tuning the composition of oxygen hyper stoichiometric ferrite Mg 0.5 Ti 0.5 Fe 2 O 4.5 for the removal of toxic organic contaminants from water.

Enhanced removal of organic contaminants by novel iron-carbon and premagnetization: Performance and enhancement mechanism.

Iron-carbon (Fe-C) microelectrolysis has attracted considerable attention in wastewater treatment due to its excellent ability to remove contaminants. Herein, novel Fe-C granules were synthesized by simple calcination method for removing organic contaminations, and a cost-effective and environmentally friendly method, namely pre-magnetization, was used to improve the micro-electrolysis performance of Fe-C. Batch experiments proved that premagnetized iron-carbon (pre-Fe-C) could significantly improve the removal of methyl orange (MO) at different Fe-C mass ratios (1:2-2:1), material dosages (1.0-2.5g/L), initial pH values (3.0-5.0), and MO concentrations (10.0-50.0mg/L). Electrochemical analysis showed that premagnetization could increase the current density and reduce the charge transfer resistance of the microelectrolysis system, making Fe-C more susceptible to electrochemical corrosion. Characterizations confirmed that the corrosion products of the materials included FeO, Fe2O3, and Fe3O4, and more corrosion products were formed in the pre-Fe-C system. Radical quenching experiments and electron spin resonance spectroscopy verified that •OH, 1O2, and O2-• were all involved in pollutant removal, and premagnetization could promote the generation of more reactive oxygen species. Overall, the pre-Fe-C process could effectively remove various organic pollutants, exhibit good adaptability to complex water environments, and hold potential for industrial applications.

Hierarchical Nanoflowers of MgFe2O4, Bentonite and B-,P- Co-Doped Graphene Oxide as Adsorbent and Photocatalyst: Optimization of Parameters by Box-Behnken Methodology.

In the present study, nanocomposites having hierarchical nanoflowers (HNFs) -like morphology were synthesized by ultra-sonication approach. HNFs were ternary composite of MgFe2O4 and bentonite with boron-, phosphorous- co-doped graphene oxide (BPGO). The HNFs were fully characterized using different analytical tools viz. X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersion spectroscopy, transmission electron microscopy, X-ray diffraction, vibrating sample magnetometry and Mössbauer analysis. Transmission electron micrographs showed that chiffon-like BPGO nanosheets were wrapped on the MgFe2O4-bentonite surface, resulting in a porous flower-like morphology. The red-shift in XPS binding energies of HNFs as compared to MgFe2O4-bentoniteand BPGO revealed the presence of strong interactions between the two materials. Box–Behnken statistical methodology was employed to optimize adsorptive and photocatalytic parameters using Pb(II) and malathion as model pollutants, respectively. HNFs exhibited excellent adsorption ability for Pb(II) ions, with the Langmuir adsorption capacity of 654 mg g−1 at optimized pH 6.0 and 96% photocatalytic degradation of malathion at pH 9.0 as compared to MgFe2O4-bentonite and BPGO. Results obtained in this study clearly indicate that HNFs are promising nanocomposite for the removal of inorganic and organic contaminants from the aqueous solutions.

Simultaneous removal of phosphorus and organic contaminants from phosphogypsum using hydrothermal method for gypsum resource regeneration

Phosphogypsum (PG) is a common chemical by-product from wet process phosphoric acid production, accumulated stockpiles of 300 million tons in China. The challenge for the comprehensive utilization of PG is thorough removal of phosphorus and organic contaminants from PG, which inevitably entails the loss of overall whiteness and limits its utilization in building materials and other fields. This work investigated the speciation of phosphorus and organic contaminants in PG by FTIR spectroscopy, Raman spectroscopy, XRD, SEM-EDS and GC-MS. On this basis, by using K2S2O8 as a mineralizer, PG was transformed into anhydrous calcium sulfate powder and the organic contaminants were fully decomposed (removal rate >80%, with residual TOC of 0.078%) under hydrothermal treatment. Under optimal hydrothermal conditions (0.3 M K2S2O8, heated at 120 °C for 12 h), the whiteness of product significantly improved from 40.9 to 97 and effective removal of phosphorus was achieved (more than 76%). The residual phosphorus in treated PG was 0.108%, which met the standard of PG as a building material in China GB/T-23456 2018 (P content < 0.2%). The mechanism study revealed that the phase transformation of calcium sulfate from dihydrate to anhydrous played a dominant role in the removal of phosphorus, H+ and SO42- from K2S2O8 decomposition facilitated the dissolution-recrystallization process of calcium sulfate, allowing the phosphorus in the lattice to escape. In addition, by thermal activation, K2S2O8 generated free radicals of SO4•- and OH• dissipated the organic contaminants in PG. This work provides theoretical and practical bases for the harmless disposal and resource recycling of industrial by-product gypsum, and it is of great significance to build the "zero-waste city".

Iron-modified biochar derived from sugarcane bagasse for adequate removal of aqueous imidacloprid: sorption mechanism study

Adsorption has been considered as a promising remediation technology to separate organic and inorganic agrochemicals from contaminated soil and water. Low-cost adsorbents, including waste derived materials, clay composites, biochar, and biochar modified materials, have attracted enormous attention for the removal of organic contaminants, including pesticides. In this study, iron-modified base-activated biochar (FeBBC) was prepared by pyrolysis (at 400 °C for 1 h) of iron-doped base (KOH) activated sugarcane bagasse for the removal of a widely used insecticide, namely imidacloprid (IMI) from water. The maximum adsorption capacity of the adsorbent (FeBBC) was calculated as 10.33 (± 1.57) mg/g from Langmuir isotherm model. The adsorbents could remove up to ~ 92% of IMI from aqueous solution at 23.8 mg/L IMI. Experimental data fitted well with the Freundlich model and pseudo-second-order model, demonstrating physisorption, as well as chemosorption, contributed to the sorption process. Even at highly acidic/basic solution pH, the FeBBC could remove substantial amount of IMI demonstrating hydrophobic interaction and pore diffusion play vital role for removal of IMI. The slight improving of IMI sorption with increasing solution pH indicated the sorption was also facilitated through ionic interaction alongside physical sorption. However, physical sorption including hydrophobic interaction and pore-filling interaction plays a vital role in the sorption of IMI.

In-situ assembled amino-quinone network of nanofiltration membrane for simultaneously enhanced trace organic contaminants separation and antifouling properties

Nanofiltration has attracted extensive attention in surface water purification and wastewater reclamation with its high permeance and effective interception of dissolved organic matter. However, the poor removal of trace organic contaminants and membrane fouling still limit its application, resulting in the potential health risk and excess energy consumption, respectively. Herein, an amine-quinone networks (AQN) coating coordinated by the 5-hydroxy-1,4-naphthoquinone (HNQ) and polyethyleneimine (PEI) was simply and facilely assembled on a commercial nanofiltration membrane. The optimum modified membrane conferred a significant increase in the rejection of trace organic contaminants (e.g., over 99% for ofloxacin). Simultaneously, the permeance of the modified membrane exhibited a slight enhancement (10%) over that of the pristine membrane thanks to the greater hydrophilicity of AQN coating without blocking pores of the polyamide layer. Static adsorption of BSA indicated that the NF-AQN membrane had excellent fouling resistance against proteins. In addition, after several cycles of dynamic fouling experiment, the higher flux recovery after physical cleaning and lower flux decline during filtration further demonstrated the outstanding antifouling property of the modified membrane. This study presents a low-cost, facile and scalable method using AQN coating for improving the performance of existing commercial nanofiltration membranes and alleviating their fouling in operation.

Enhanced degradation of DDT using a novel iron-assisted hydrochar catalyst combined with peroxymonosulfate: Experiment and mechanism analysis

Poplar wood (PW) hydrochar modified by iron (Fe@HC) was prepared greenly by one-step hydrothermal method. The adsorption and degradation performance of DDT was investigated in a heterogeneous advanced oxidation system (Fe@HC/PMS) formed by Fe@HC collaborated with peroxymonosulfate (PMS). The effects of Fe@HC dosage, PMS dosage and DDT initial concentration were quantitatively analyzed. The results showed that DDT removal efficiency can reach to 88.62% in 240 min under optimal conditions (4 g/L Fe@HC, 10 mM PMS, 0.5 mg/L DDT, 5.5 pH0) in Fe@HC/PMS system. Furthermore, Fe@HC/PMS system exhibited high degradation rate and TOC removal efficiency for the removal of various organic contaminants. The influence mechanisms of Fe@HC/PMS system on DDT adsorption and degradation were proposed based on electron paramagnetic resonance (EPR) testing analysis and radical quenching experiments. Based on the mechanism analysis, the influence of Fe@HC/PMS on DDT removal efficiency can be concluded in the order: Active substance indirect degradation (60.95%) > Fe@HC direct degradation (10.13%) > Fe@HC adsorption (17.54%). Among active substance indirect degradation, SO4•−, •OH, O2•− and 1O2 occupied 27.56%, 15.74%, 5.33% and 12.32%, respectively. Moreover, DDT degradation intermediates were detected by a gas chromatography-mass spectrometer (GC-MS) to predict DDT degradation pathways. This study provided a green progress for the reuse of biomass resources and a new way for the enhanced degradation of DDT.

Highly efficient removal of organic contaminant with wide concentration range by a novel self-cleaning hydrogel: Mechanism, degradation pathway and DFT calculation

A novel carbon nitride based self-cleaning hydrogel photocatalyst (KI-PCN gel, potassium and iodine co-doped carbon nitride confined in alginate) has been successfully constructed by a facile method. Fabricated photocatalyst showed enhanced synergistic adsorption-photocatalytic degradation property on a high concentration of methylene blue (HMB) because of enhanced carrier separation efficiency and improved light adsorption capacity of KI-PCN. As expected, the KI-PCN gel showed the highest apparent rate constant value (Kapp =0.0310 min−1), which was about 38.8 and 5.8 times as that of blank hydrogel (Kapp=0.0008 min−1) and PCN gel (Kapp=0.0053 min−1), respectively. Meanwhile, KI-PCN gel can continuously adsorb low concentration of MB (LMB), and the MB-adsorbed KI-PCN gel can self-clean under light irradiation. The bench-scale experiments simulating real river showed that KI-PCN gel can effectively and continuously remove LMB (0.1–20 ppm), indicating the possibility for the removal of contaminants in natural rivers. Furthermore, the possible degradation pathways were proposed by combining the density functional calculations (DFT) and intermediates identified by liquid chromatography-mass spectrometry (LC-MS). This work proposed a new perspective to acquire a novel self-cleaning and easily recyclable photocatalyst for treatment of wide concentration range organic wastewater as well as remediation of natural waterbody.

Facile synthesis of CdO-ZnO heterojunction photocatalyst for rapid removal of organic contaminants from water using visible light

The synthesis of an efficient photocatalyst for removing organic contaminants in the water is of major importance for researchers working in heterogeneous photocatalysis. To do this, we provide the co-precipitation approach for synthesizing heterojunction nanocomposite (CdO-ZnO). Standard analytical techniques were used to characterize the synthesized components. According to the XRD and DRS results, a composite of ZnO and CdO was effectively synthesized with a shift of λmax towards the higher wavelength. SEM pictures reveal well-decorated oval-shaped CdO nanoparticles with hexagonal ZnO particle morphology. Under visible light irradiation, the as-prepared CdO-ZnO nanocomposite demonstrated very efficient photocatalytic performance as measured by the decomposition of RhB, MB, paracetamol, and ciprofloxacin in an aqueous solution. The photo-mineralization of MB and RhB over the most active CZ-3 catalyst was also assessed by measuring the decrease in TOC (total organic carbon) content over time when exposed to visible light. The breakdown of paracetamol produces no hazardous by-products, according to high-performance liquid chromatography (HPLC) study. The photocatalytic process appears to be dominated by OH and h+, according to the radical scavenger tests.

Copolymer-MnO2 nanocomposites for the adsorptive removal of organic pollutants from water.

The copolymer beads prepared by suspension polymerisation were decorated with MnO2 nanoparticles and successfully implemented for the efficient removal of toxic organic contaminants from water. Copolymer-MnO2 nanocomposite was further analysed using XRD, SEM and optical microscope. The SEM images showed the surface characteristics of MnO2 nanoparticles on copolymer beads. The efficiency of the copolymer-MnO2 nanocomposite for the removal of model pollutant methylene blue and rhodamine B is then analysed by changing the concentration of pollutant. The results obtained exhibited 18.45mg/g for methylene blue adsorption and 3.125mg/g for rhodamine B. The adsorption equilibrium results were fitted to Langmuir adsorption isotherm for both methylene blue and rhodamine B adsorption. The desorption studies were performed for five consecutive cycles, and material was showing good regenerating capacity towards both organic pollutants. The obtained results show that copolymer-MnO2 nanocomposite is an efficient material for the removal of organic contaminants from wastewater.

Ultrasonic Energy as an Agent to Aid Water Treatment in the Coagulation Process

The aim of the study was to estimate the effectiveness of ultrasonic coagulation aiding. The effect of ultrasound exposure alone and associated systems (ultrasound exposure/coagulant) on the contamination of natural water was examined. The evaluation of the test results was based on changes in indicators, such as TOC, color, turbidity, and electrokinetic potential. Three different coagulants were used in the tests of associated systems. The tests included basic processes related to volumetric coagulation, such as agitation, flocculation, and sedimentation. Sonication of water samples was carried out at a constant frequency of 22 kHz, variable vibration amplitude of 8–16 μm, and an exposure time of 1–5 min. The most efficient removal of organic contaminants from the water tested was achieved at a maximum amplitude of A = 16 μm, with effectiveness reaching 29% (TOC). In the tests of the associated systems, the effect of ultrasound exposure on the removal of water turbidity (an increase in the effectiveness of 25–35%) was generally greater than that on water color (8–21%). This relationship reflects the differentiated effect of ultrasonic energy on colloids of different stability. In removing turbidity, ultrasound exposure had the most favorable effect on aluminum sulfate. In respect of color, a better result was obtained using the modified coagulant. The possibility of reducing the coagulant dose confirmed the aiding effect of ultrasound. In the coagulation process, ultrasound exposure has a positive effect on the course of flocculation and the sedimentation of suspensions. In addition to the reduction in the doses of chemical reagents, it also leads to the modification of the post-coagulation sludge structure.

Synthesis and characterization of amino functionalized bimetallic metal-organic frameworks as peroxymonosulfate activator for water purification: Performance and mechanistic studies

The importance of new water purification technology for maintaining clean water resources and a high quality of life is self-evident. In this study, amino functionalized bimetallic metal-organic frameworks (NH2-MIL-101(FeCo)) were prepared to activate peroxymonosulfate (PMS) for removal of organic pollutants from water. The structure, morphology, and physicochemical properties of as-prepared NH2-MIL-101(FeCo) were comprehensively evaluated by X-ray diffraction, scanning electron microscopy, N2 adsorption-desorption isotherms, and X-ray photoelectric spectroscopy. Degradation tests were performed to study effects of PMS concentration, catalyst dosage, initial pH, and common substances on the orange G (OG) removal. The acidic and alkaline conditions promoted the formation of mesoporous structures in NH2-MIL-101(FeCo) and enhanced the mass transfer processes to remove OG. 100% of OG was removed through a rate constant of 0.0711 min-1 within 45 min in NH2-MIL-101(FeCo)− 2/PMS/OG system, where 1O2, SO4•−, and ·OH played pivotal contributions in the OG removal. The catalytic activity of NH2-MIL-101(FeCo) originated from unsaturated metal sites of Fe(II) and Co(II). This work demonstrates a feasible strategy towards the synthesis of functional MOFs for removal of organic contaminants.