Remediation Of Polluted Water Research Articles

Highly efficient activation of peroxymonosulfate by cobalt ferrite anchored in P-doped activated carbon for degradation of 2,4-D: Adsorption and electron transfer mechanism

The dispersing effect of carbon materials on nanoparticles can enhance the full exposure of their active sites. Herein, phosphorus (P)-doped activated carbon-supported trace cobalt ferrite composites (P-CoFe@BCX) were achieved by two-step pyrolysis for efficient peroxymonosulfate (PMS) activation and water pollution remediation. The removal efficiency of 2,4-dichlorophenoxyacetic acid (2,4-D) was optimized by adjusting the coupling ratio of carbon substrate and cobalt ferrite. P-CoFe@BC5/PMS oxidation system (0.10 g L-1, 0.50 mM) eliminated 98.3% of 2,4-D (20.0 mg L-1) within 60 min at unadjusted pH. The constructed adsorption enrichment and oxidative degradation pathways are highly efficient in utilizing reactive oxygen species (ROS), and the dual tracks of free and non-free radicals achieve the rapid degradation of 2,4-D. P-doped activated carbon acts as an electron shuttle to accelerate electron transfer between active sites and enhances the adsorption efficiency of 2,4-D and PMS onto the composites. In addition, the P-CoFe@BC5/PMS oxidation system still exhibited strong 2,4-D removal performance at a wide pH range of 2.0–10.0. The inhibitory effect of environmental components was related to their concentration, such as chloride, bicarbonate, sulfate and humic acid. Density functional theory calculations show that ROS tends to attack the CO bond on the 2,4-D branch chain, and the degradation products show lower biological toxicity. Hence, the constructed cobalt ferrite anchored P-doped activated carbon activated PMS system has great potential in treating organic wastewater.

Biomimetic Guided Bi2WO6/Bi2O3 Vertical Heterojunction with Controllable Microstructure for Efficient Photocatalysis

To bridge the technical gap of heterojunction induction control in conventional semiconductor photocatalysts, a method of regulating the growth of heterojunctions utilizing biomimetic structures was designed to prepare a series of Bi2WO6/Bi2O3 vertical heterojunction nanocomposites for the disposal of environmentally hazardous tetracycline wastewater difficult to degrade by conventional microbial techniques. Porous Bi2O3 precursors with high-energy crystalline (110) dominant growth were produced using the sunflower straw bio-template technique (SSBT). Bi2WO6 with a (131) plane grew preferentially into 2.8 to 4 nm pieces on the (110) plane of Bi2O3, causing a significant density reduction between Bi2WO6 pieces and a dimensional decrease in the agglomerated Bi2WO6 spheres from 3 μm to 700 nm since Bi2WO6 grew on the structure of the biomimetic Bi2O3. The optimal 1:8 Bi2WO6/Bi2O3 coupling catalyst was obtained via adapting the ratio of the two semiconductors, and the coupling ratio of 1:8 minimized the adverse effects of the overgrowth of Bi2WO6 on degradation performance by securing the quantity of vertical heterojunctions. The material degradation reaction energy barrier and bandgap were significantly reduced by the presence of a large number of vertical heterojunction structures, resulting in a material with lower impedance and higher electron-hole separation efficiency; thus, the degradation efficiency of 1:8 Bi2WO6/Bi2O3 for tetracycline hydrochloride reached 99% within 60 min. In conclusion, this study not only successfully synthesized a novel photocatalyst with potential applications in water pollution remediation but also introduced a pioneering approach for semiconductor-driven synthesis.

Sputter -coated N-enriched mixed metal oxides (Ta2O5-Nb2O5-N) composite: A resilient solar driven photocatalyst for water purification

This study demonstrated the formation of N-enriched mixed metal oxides (Ta2O5-Nb2O5-N and Ta2O5-Nb2O5) thin film composites used as photocatalysts to degrade P-Rosaniline Hydrochloride (PRH-Dye) dye under solar radiation. By controlling the N gas flow rate during the sputtering process, the N concentration in the Ta2O5-Nb2O5-N composite is significantly included, and demonstrated by XPS and HRTEM analysis. With the help of XPS and HRTEM investigations, it was determined that the addition of N to Ta2O5-Nb2O5-N significantly enhances the active sites. The Ta-O-N bond (N 1 s and Ta 4p3/2 spectra) was verified by the XPS spectra. Ta2O5-Nb2O5 was found to have a lattice interplanar distance (d-spacing) of 2.52, whereas Ta2O5-Nb2O5-N showed the 2.5 (620 planes). A sputter-coated Ta2O5-Nb2O5and Ta2O5-Nb2O5-N photocatalysts were prepared, and their photocatalytic activity was evaluated using PRH-Dye as a model pollutant under solar radiation by adding H2O2 (0.01 mol). The photocatalytic activity of the Ta2O5-Nb2O5-N composite was compared with TiO2 (P-25) and Ta2O5-Nb2O5. Ta2O5-Nb2O5-N showed very high photocatalytic activity compared to Degussa P-25 TiO2 and Ta2O5-Nb2O5 under solar radiation and confirmed the presence of N in Ta2O5-Nb2O5-N significantly increased the generation of ˙OH radicals (in pH 3, 7 and 9). With the use of LC/MS, the stable intermediates or metabolite created during the photooxidation of PRH-Dye were assessed. The results of this study will provide useful insights on how Ta2O5-Nb2O5-N influences the efficiency of water pollution remediation.

Hierarchical 3D Flower-like Metal Oxides Micro/Nanostructures: Fabrication, Surface Modification, Their Crucial Role in Environmental Decontamination, Mechanistic Insights, and Future Perspectives.

Hierarchical micro/nanostructures are constructed by micro-scaled objects with nanoarchitectures belonging to an interesting class of crystalline materials that has significant applications in diverse fields. Featured with a large surface-to-volume ratio, facile mass transportation, high stability against aggregation, structurally enhanced adsorption, and catalytical performances, three dimenisional (3D) hierarchical metal oxides have been considered as versatile functional materials for waste-water treatment. Due to the ineffectiveness of traditional water purification protocols for reclamation of water, lately, the use of hierarchical metal oxides has emerged as an appealing platform for the remediation of water pollution owing to their fascinating and tailorable physiochemical properties. The present review highlights various approaches to the tunable synthesis of hierarchical structures along with their surface modification strategies to enhance their efficiencies for the removal of different noxious substances. Besides, their applications for the eradication of organic and inorganic contaminants have been discussed comprehensively with their plausible mechanistic pathways. Finally, overlooked aspects in this field as well as the major roadblocks to the implementation of these metal oxide architectures for large-scale treatment of wastewater are provided here. Moreover, the potential ways to tackle these issues are also presented which may be useful for the transformation of current water treatment technologies.

Removal of nitrate nitrogen from wastewater by green synthetic hydrophilic activated carbon supported sulfide modified nanoscale zerovalent Iron: Characterization, performance and mechanism

In this study, A green reducing agent green tea extract is used instead of traditional sodium borohydride and porous activated carbon was supported to prepare nano-zero valent iron (nZVI) combined with sulfate (GT-PAC-nZVI/S) to remove Nitrate Nitrogen (NO3–-N) in wastewater. SEM-EDS, BET, XRD and FTIR characterization results confirmed that effective preparation of porous and high specific surface area and successful loading of sulfide nZVI on PAC. Batch experiments were conducted to measure the effects on the removal of nitrate nitrogen of different parameters including pH, temperature, dosage, interfering agents, carbon-iron ratio and iron-sulfur ratio. The experimental results demonstrate that GT-PAC-nZVI/S has a high nitrate nitrogen removal rate and reduction product gaseous nitrogen can reach 93.00% and 22.10%, respectively, at pH = 7, the dosage of GT-PAC-nZVI/S = 4 g/L, temperature of 60 ℃, iron-sulfur ratio = 1:0.3 and time of 95 min. And interfering ion HPO42- have the strong inhibition for NO3–-N degradation. The adsorption isotherm and kinetic data for GT-PAC-nZVI/S was fitted well with the Langmuir and pseudo-second order model, respectively, indicating that the adsorption process for nitrate was chemisorption. Furthermore, GT-PAC-nZVI/S enhanced the removal of nitrate nitrogen through complexation, redox, and adsorption co-precipitation. This work highlights the efficient remediation of nitrate-nitrogen water pollution by porous activated carbon loaded with sulfide nZVI.

Constructing outstanding 1D/2D Co3O4/NiMnO3 heterostructure to promote the PEC efficiency for water pollution remediation

The structural design and morphology control of materials is a very attractive topic because the structure and morphology of materials usually play a key role for their performance and application. In this work, we report a facile two-step hydrothermal process for construction of the binary composite oxide system (i.e., 1D/2D Co3O4/NiMnO3 core-shell heterostructure) based on Ostwald ripening effect. Interestingly, Co3O4 nanowire will expand only when it is fully covered with NiMnO3 nanosheets to form a core-shell structure in sequential hydrothermal process. In binary composite oxide system, the formation of continuous and uniform interface between core (Co3O4) and shell (NiMnO3) based on Ostwald ripening effect is the key factor in the heterogeneous nucleation process, which can be proved by the homogeneous diffusion of Co element in the Ti/Co3O4-NiMnO3 sample. As a result, the optimized Ti/Co3O4-NiMnO3-1.5 exhibited superior PEC performance (degradation rates are ∼ 91.2% for 120 min and 80.5% after 5 cycles) for degrading reactive brilliant blue KN-R solution, which can be attributed to the construction of the hollow Co3O4/NiMnO3 core-shell heterostructure. Furthermore, the identification experiments of active species showed that the h+ and •O2- radicals are the dominant reactive species, indicating the induced charge transfer is based on the type II semiconductor heterostructure.

Nanostructured Gallium Nitride Membrane at Wafer Scale for Photo(Electro)catalytic Polluted Water Remediation (Adv. Sci. 6/2023)

Nanostructured Gallium Nitride Membrane at Wafer Scale for Photo(Electro)catalytic Polluted Water Remediation (Adv. Sci. 6/2023)

Mesoporous CdTe supported SiO2-TiO2 nanocomposite: Structural, optical, and photocatalytic applications

Owing to polluted water remediation, semiconductor nano photocatalysis has been considered a promising methodology. However, low reaction rates and high electron-hole recombination have impeded their large-scale applications. Therefore, heterogeneous nano photocatalysts are required for promoting their functional applications. Here, sol-gel-based mesoporous titania nanoparticles (TNPs) and silica-titania nanocomposite (STNC) are synthesized and supported with CdTe (CdTe/STNC) for photocatalytic applications. Vapor pressure scanning electron microscopy (VPSEM) exhibited the porous and colonial nanostructure of CdTe supported STNC catalyst. The high-resolution transmission electron microscopy (HRTEM) possessed a spherical morphology with particle size 5.6 nm of TNPs, 2.6 nm of STNC, and 2.1 nm of CdTe/STNC. Moreover, the CdTe/STNC catalyst exhibited a large surface area (SBET) ∼ 410 m2/g and pore size distribution ∼ 1.8 nm. The CdTe/STNC exhibited high photocatalytic activity with methylene blue degradation of 95% (k = 0.01 min−1) after 180 min of ultraviolet radiation.

Polymerized stimuli-responsive microgels for the removal of organic dye from water

Polymerized hydrogel materials (PGM) containing uniform-sized stimuli-responsive microgel particles could be promising alternatives for solution-based microgels to remove organic dyes from water. In the current work, PGM is prepared using Poly(N-isopropylacrylamide-co-acrylic acid) based anionic microgels and their ability for uptake and release studies with an oppositely charged dye, methylene blue (MB) is carried out using UV–vis spectroscopy. The mechanism of dye adsorption is understood at a single particle level using light scattering, and zeta potential and the contributions from different molecular interactions among dye molecules and constituting entities of microgels are obtained from molecular docking studies. The maximum dye uptake by PGM is around 80 % in the swollen state (at pH 7 and 20 °C). In contrast, the dye release studies in the deswollen state (at pH 3 and 50 °C) show a decrease in the release efficiency from 87 % to 63 % of the total dye adsorbed in 4-repeated cycles. The adsorption isotherm follows a sigmoidal (S) model that has been majorly used in different multi-layer adsorption systems. Extensive dynamic and static light scattering studies demonstrate a deswelling of hydrodynamic radius and core–shell radius of microgels at low temperatures (20 °C) induced by dye adsorption. At higher temperatures, the dye-adsorbed microgels have a higher hydrodynamic radius than the pure microgels due to the remaining dye molecules within the microgel that do not release even in the deswollen state. Molecular docking studies show that electrostatic interaction dominates between COO– and MB and van der Waals/hydrophobic dominates for MB-NIPAM and MB-COOH docking complex respectively. Our work covering adsorption/desorption properties of the material to the single-particle level can provide a better understanding in formulating reusable smart materials for the remediation of different water pollutants.

Nanoscale Zero-Valent Iron Dispersed by Sodium Alginate Enables Highly Efficient Removal of Lead (Pb) from Aqueous Solution

Nanozero-valent iron (NZVI) shows great potential in the remediation of water pollution, but its application is limited by its instability and tendency to aggregate. To enhance the dispersibility and antioxidant properties of NZVI, we prepared composites (SN) by wrapping NZVI with sodium alginate (SA) for the removal of Pb(II) from water. Various characterization methods such as SEM-EDS, BET, XPS, and FT-IR were used to study the structure of the materials, and the adsorption properties of Pb(II) in the materials were analyzed using adsorption kinetics and adsorption isotherm experiments. The results showed that SN had a specific surface area of 47.05 m2/g, which was significantly higher than the 7.56 m2/g of NZVI, and the surface passivation was reduced. The maximum adsorption amount of SN on Pb(II) was obtained by fitting the adsorption isotherm model at 70.92 mg/g. After five cycles of adsorption, SN exhibited a removal rate of 95.11% for Pb(II). The mechanism of Pb(II) removal by SN involved the synergistic effect of electrostatic adsorption, redox reaction, ion exchange, and coprecipitation. Notably, even after 90 days of aging, the removal rate of Pb(II) by SN remained high at 95.39%, demonstrating good reactivity. These results indicated that SN is an effective adsorbent to remove Pb(II) contamination.

CdTe QD-decorated GO nanosheet heterojunction for efficient photocurrent generation and photocatalytic activity.

Cadmium telluride quantum dot (CdTe QD)-decorated graphene oxide (GO) nanosheets are promising heterojunctions for the environmental remediation of organic pollutants in water. However, assembling these two materials is a challenge. For this purpose, we have developed a one-step approach for the decoration of QDs onto the surface of GO nanosheets/intercalation of QDs into GO nanosheets through self-assembly, resulting in the formation of sandwiched hybrid heterojunctions. After synthesis, the samples were analysed for variations in their structural, morphological, compositional, optical and photoelectrochemical characteristics using various analytical tools. Interlinking QDs and GO nanosheets enhanced the photocurrent generation (∼5.8 μA cm-2), resulting in faster electron transfer by delaying the decay time (58.25 ms). A higher rate constant value (k = 0.135 min-1) was obtained for degrading 93% MB dye in 20 min. This work demonstrates a cost-effective strategy for constructing CdTe QDs/GO nanosheet hybrid heterojunctions for potential application in the field of photocatalysis.

Phytochemical Analysis of Wrightia tinctoria Leaves and Synthesis of ZnO Nanoparticles for the Remediation of Water Pollutants

In this work, zinc oxide nanoparticles (ZnO NPs) were fabricated using aqueous extract of Wrightia tinctoria leaves for evaluating its catalytic and antibacterial efficacy against water contaminants. The qualitative phytochemical estimation showed the presence of secondary metabolites alkaloids, tannins, terpenoids, steroids, glycosides, flavonoids and biomolecules carbohydrates and proteins in different solvent extracts. The quantitative estimation for phytochemicals showed total phenols (39.59 mg/g), total flavonoids (44.34 mg/g), total alkaloids (149.56 mg/g) and total tannins (56.47 mg/g). The GC-MS analysis revealed the bioactive compound mome inositol as the major phytochemical present in W. tinctoria leaves. The characterization of ZnO nanoparticles with XRD showed Bragg’s reflections at 2θ angles of 31.76º, 34.47º, 36.23º, 47.48º, 56.59º, 62.99º and 68.00º which confirmed the hexagonal wurtzite structure and size (86 nm) of the nanoparticles. The SEM analysis showed that the morphology of synthesized was spherical structure with uniform distribution. The ZnO nanoparticles effectively inhibited the growth of water contaminating bacterial pathogens viz. Escherichia coli, Staphylococcus aureus, Klebshiella pneumoniae and Streptococcus pneumoniae. The photocatalytic activity of ZnO oxide nanoparticles in degrading textile dyes, methylene blue and methyl orange was found to be effective.

Green Synthesis of Nano-Semiconductor Photocatalysts and their Effectivity for Photo-Oxidation of Organic Pollutants in Wastewater: A Review Study

In recent years, green synthesis of nanoparticles (NPs) has been regarded as preferable and acceptable than chemical approaches, particularly when it applies to pollution control and wastewater treatment. The green synthesis approaches were effectively employed to prepare a huge number of semiconductors photocatalysts, such as TiO2 , WO3 , SnO2 , CeO2 , ZnO, Bi2 O3 , Ag, Na2 SeO3 , ZnCr2 O4 , Nb2 O5 , and so on. Photocatalytic degradation is an advanced water treatment technology that has great potential for the photo-oxidation of various organic pollutants and various types of nano-semiconductors photocatalysts. Plant waste has the potential to be more useful in the green synthesis of metal nanoparticles (NPs) due to their availability, high biodiversity, eco-friendliness, and low cost. This review focuses on the employing of plant extracts in the synthesis of nano-photocatalysts as a cost-effective approach. Our study involves reviewing a huge number of impactful studies that deal with the photooxidation of organic pollutants under light radiation. It was concluded that the utilization of waste plants in the green synthesis of nano-photocatalysts is a low-cost technology, environmentally friendly, and can produce nanoparticles with outstanding efficiency for water pollution remediation. This study encourages the development of new technologies based on reusing plant waste in the synthesis of economic photocatalysts for environmental applications.

Bimetallic FeNi Alloy Nanoparticles Grown on Graphene for Efficient Removal of Congo Red From Aqueous Solution

AbstractNano zero‐valent iron (nZVI) is an effective material for dye wastewater treatment, but excessive agglomeration and oxidation greatly limit its application. Herein, graphene (GR) supported FeNi bimetallic nanoparticles (FeNi@GR) are prepared by alloying and carrier supported dispersion for efficient removal of azo dyes from water. Not only can it effectively solve the problem of excessive agglomeration and oxidation of nZVI, but also the synergistic effect of bimetallic coordination formation and the excellent electron transfer ability of graphene are beneficial to enhance the reactivity of FeNi@GR. The optimal FeNi@GR is prepared by adjusting the content of GR and the removal of Congo red (CR) by FeNi@GR‐10% reached 625 mg g−1 within 150 min at pH = 7.0. Higher temperature and lower pH favor the removal of CR azo dye. The action mechanisms of FeNi@GR presumably involve the transfer of active hydrogen atoms and the transfer of electrons generated by Fe0 and Ni0. Besides, the saturation magnetization (Ms) of FeNi@GR is 68.15 emu g−1, which has excellent magnetic response performance. This work not only provides a simple and efficient method to stabilize nZVI, but also reveals that using FeNi@GR is a promising approach for the remediation of water pollution.

Nanostructured Gallium Nitride Membrane at Wafer Scale for Photo(Electro)catalytic Polluted Water Remediation.

Photo(electro)catalysis methods have drawn significant attention for efficient, energy-saving, and environmental-friendly organic contaminant degradation in wastewater. However, conventional oxide-based powder photocatalysts are limited to UV-light absorption and are unfavorable in the subsequent postseparation process. In this paper, a large-area crystalline-semiconductor nitride membrane with a distinct nanoporous surface is fabricated, which can be scaled up to a full wafer and easily retrieved after photodegradation. The unique nanoporous surface enhances broadband light absorption, provides abundant reactive sites, and promotes the dye-molecule reaction with adsorbed hydroxyl radicals on the surface. The superior electric contact between the nickel bottom layer and nitride membrane facilitates swift charge carrier transportation. In laboratory tests, the nanostructure membrane can degrade 93% of the dye in 6 h under illumination with a small applied bias (0.5V vs Ag/AgCl). Furthermore, a 2 inch diameter wafer-scale membrane is deployed in a rooftop test under natural sunlight. The membrane operates stably for seven cycles (over 50 h) with an outstanding dye degradation efficiency (>92%) and satisfied average total organic carbon removal rate (≈50%) in each cycle. This demonstration thus opens the pathway toward the production of nanostructured semiconductor layers for large-scale and practical wastewater treatment using natural sunlight.

MOFs-derived Mn/C composites activating peroxymonosulfate for efficient degradation of sulfamethazine: Kinetics, pathways, and mechanism

Both manganese oxides (MnOx) and carbon materials hold promise for persulfate activation to remediate polluted waterbodies. However, the aggregation of MnOx during the calcination synthesis and lower activity to persulfate of carbon materials seriously limit their industrial application. In this work, two Mn/C composites (MnOx-NA and MnOx-A) were synthesized from manganese-metal organic frameworks (MOFs) under nitrogen atmosphere and air atmosphere calcination respectively. The prepared MnOx-NA exhibited more excellent peroxymonosulfate (PMS) activation performance than MnOx-A, and almost 100% sulfamethazine (SMT) could be removed by the MnOx-NA/PMS system within 30 min. Moreover, the MnOx-NA/PMS system exhibited impressive stability even after 10 cycles and displayed high anti-interference ability to Cl−, ClO4−, CO32−, SO42−, NO3− and humic acid (HA). In addition, the oxidation system could efficiently remove SMT in different aqueous matrices. Three possible pathways of SMT degradation were proposed according to the LC-MS analysis. Electron paramagnetic resonance (EPR), quenching experiments, and cyclic voltammetry experiments revealed that SMT degradation predominantly occurred through a catalyst-mediated electron transfer pathway. Material characterization and electrochemical impedance spectroscopy (EIS) analysis showed that the derived carbon species strengthened the MnOx-NA's electron-transfer capability and promoted the uniform distribution of MnOx particles on the carbon materials surface, which significantly improved MnOx-NA's PMS activation performance. This study introduces a facile method for the design of Mn/C composites PMS activator and provides theoretical guidance for water pollution remediation.

Advancing n-π* electron transition of carbon nitride via distorted structure and nitrogen heterocycle for efficient photodegradation: Performance, mechanism and toxicity insight

To adequately utilize solar energy for water pollution remediation, tailoring graphite carbon nitride (CN) with sufficient active sites exposure, visible-light harvest and eminent charge separation/migration/recombination efficiency, has long been pursuing. Herein, a pyrazine doped distorted architecture CN with advancing n-π* electron transition was tailored via one-pot thermal-melting assemble following thermal-induce copolymerization of pyrazine-2,3-dicarboxylic acid and urea. Various characterizations verify the successful construction of distorted porous thin wall CN. The nitrogen adsorption–desorption, photoelectric and band structure analysis manifest that the optimized 20-PACN sample possesses propelled visible-light capture ability with wavelength above 500 nm, more active sites exposure with high specific surface area and hybrid electron structure with distinctly improved charge separation/migration/recombination efficiency. More importantly, 10 mg of 20-PACN can photodegradation 97 % of tetracycline (91 % of rhodamine B or 91 % of methylene blue) within 100 min, which is 7.1 times of bulk counterparts. ESR and quenching tests confirm that apart from h+, ⋅O2– and 1O2 significantly assist to the photodegradation reaction, which profit from upshifted CB and the appearance of intermediate state. The mass spectrum, toxicity prediction and on-line infrared spectroscopy explicated intermediates, routes and toxicity, as well as real-time monitor the variation of functional groups during photodegradation reaction. At last, combined the above test characterization and density functional theory analysis, a potential propelled mechanism of photodegradation was proposed.

Adsorptive remediation of wastewater pollutants using different nanomaterials

Water is an essential element for human resources. The contamination of water with toxic pollutants is the biggest global challenge. Water is contaminated with various toxic inorganic (heavy metals) and organic (dyes) pollutants. Water pollution is primarily created by human-made activities, including household, agricultural and industrial waste. Nanotechnology is promising to ensure safe and healthy drinking water. The review provides a brief overview of recent nanomaterials developments, such as their usage as nano adsorbents, for water treatment processes. Nanomaterials have high adsorption capacity due to their higher surface-to-volume ratio. The main focus of this review article is on the adsorptive remediation of water pollutants. Nanomaterials for adsorptive remediation of pollutants (heavy metals and dyes) are categorized as organic (carbon and graphene-based) and inorganic (metals and metals oxides-based) nanomaterials. They can be modified with different functional groups to increase their adsorption capacity. The adsorption capacity of nanomaterials to adsorb the pollutants depends on pH, adsorbent dosage, contact time, and initial pollutants concentration. The nanomaterials provide a powerful alternative to conventional treatment approaches due to improved adsorption capacity. However, nanotechnology needs to overcome the environmental concerns and cost-effectiveness of nanomaterials. The regeneration and reuse of nanomaterials can enable it.

Transient absorption spectroscopy insights into heterogeneous photocatalysis for water pollution remediation

Transient absorption studies have contributed to our current understanding of heterogeneous photocatalytic systems. Insights have been gained into the nature of the photogenerated charge carriers and their trapping, their subsequent transfer to the reaction medium, the transformations and kinetics that ensue from transient species to the final reaction products, and equally important the time scales at which these events occur. In this review, the focus is on learnings relevant to heterogeneous photocatalytic systems for water pollution remediation. It is subdivided into sections on TAS studies of heterogeneous photocatalysis for: Dye degradation (Section 2.0); Organic pollutant degradation (Section 3.0); and Inorganic pollutants removal (Section 4.0). The majority of the studies has been on heterogenous TiO2 photocatalysis, but more recently novel photocatalytic materials such as doped and heterostructured materials have also been studied. Those latter systems have great potential for the development of solar driven heterogeneous photocatalysis for environmental remediation.

Preparation and characterization of sodium polyacrylate grafted montmorillonite nanocomposite for the adsorption of cadmium ions form aqueous solution

High-efficiency adsorbents made from clay minerals have a wide application in remediation of soil and water pollution, especially in the treatment of refractory and highly toxic heavy metals. Montmorillonite itself has a good adsorption capacity and a large modification space for its layered structure. Therefore, carboxylate polymer grafted montmorillonite was developed to improve the adsorption capacity of heavy metals in this paper. Two kinds of modified preparation routes were compared, and a series of batch adsorption tests were conducted to evaluate the influence degree of parameters (contact time, pH, temperature, and cadmium concentration). The structural changes of montmorillonite samples before and after modification were characterized by a series of microscopic analyses and measurement techniques. The results show that the silicon hydroxyl produced by the hydrolysis of silane coupling agent can indeed be grafted by dehydration condensation with Si/Al-OH on clay surface. The grafting chain can be greatly increased by C=C double bond breaking polymerization. The polycarboxylate group can effectively improve the adsorption performance of modified montmorillonite for cadmium ions. The maximum adsorption capacity of modified montmorillonite increased by about 224.75%, reaching 63.49 mg/g. The adsorption model of montmorillonite conforms to Langmuir monolayer adsorption model, while modified montmorillonite samples exhibit Freundlich adsorption model and S-type isothermal adsorption curve characteristics of resin. The preparation method of neutralizing after polymerization of acrylic acid was proposed to be better, which provides technical guidance for scientific and efficient application.