Performance of a solar photocatalysis reactor as pretreatment for wastewater via UV, UV/TiO2, and UV/H2O2 to control membrane fouling

Advanced photocatalysis as a viable and sustainable wastewater treatment process: A comprehensive review

In our era, water pollution not only poses a serious threat to human, animal, and biotic life but also causes serious damage to infrastructure and the ecosystem. A set of physical, chemical, and biological technologies have been exploited to decontaminate and/or disinfect water pollutants, toxins, microbes, and contaminants, but none of these could be ranked as sustainable and scalable wastewater technology. The photocatalytic process can harmonize the sunlight to degrade certain toxins, chemicals, microbes, and antibiotics, present in water. For example, transition metal oxides (ZnO, SnO2, TiO2, etc.), when integrated into an organic framework of graphene or nitrides, can bring about more than 90% removal of dyes, microbial load, pesticides, and antibiotics. Similarly, a modified network of graphitic carbon nitride can completely decontaminate petrochemicals. The present review will primarily highlight the mechanistic aspects for the removal and/or degradation of highly concerned contaminants, factors affecting photocatalysis, engineering designs of photoreactors, and pros and cons of various wastewater treatment technologies already in practice. The photocatalytic reactor can be a more viable and sustainable wastewater treatment opportunity. We hope the researcher will find a handful of information regarding the advanced oxidation process accomplished via photocatalysis and the benefits associated with the photocatalytic-type degradation of water pollutants and contaminants.

Sandwich-structured continuous ZIF-8/Ti3C2 MXene/ZIF-8 for efficient sterilization: Enhanced photocatalytic activity, photothermal effect, and environmental safety

The development of effective water purification systems is crucial for controlling and remediating environmental pollution, especially in terms of sterilization. Herein, we demonstrate elaborately designed composite nanosheets with a sandwich structure, composed of two-dimensional (2D) Ti3C2 MXene nanosheet core and conformal ZIF-8 ultrathin outer layers, and their potential applications in photocatalytic sterilization. The study results indicate that the conformal ZIF-8-MXene nanosheet exhibits an expanded light absorption range (826 nm), improved photothermal conversion efficiency (6.2 °C s-1), and photocurrent response, thus boosting photocatalytic sterilization efficiency (6.63 log10 CFU mL-1) against Escherichia coli under simulated sunlight within 90 min. Interestingly, 2D ZIF-8 layers exhibit positive zeta potential (19 mV), good hydrophilicity (40.6°), and local photogenerated-hole accumulation, possessing efficient bacteria-trapping efficiency. Membrane filters fabricated from optimized composite nanosheets exhibit an outstanding bacteria-trapping and sterilization efficiency (almost 100 %) against Escherichia coli under simulated sunlight within 30 min of the flow photocatalytic experiments. This work not only presents a rational structural design of the conformal and ultrathin anchoring of ZIF-8 onto a 2D conductive material for bacteria-trapping and sterilization, but also opens new opportunities for using metal-organic frameworks in photocatalytic disinfection of drinking water.

Calcium-doped magnetic humic acid nano particles for the efficient removal of heavy metals from wastewater: the role of Ca

Ca doping is an effective method for improving the adsorption capacity of HA-Fe aggregates and regulating their structures. Understanding the structural characteristics of Ca-HA-Fe aggregates can help explore their microscopic adsorption effect on heavy metals. However, the heterogeneity of HA results in an incomplete understanding of the structural characteristics of the ternary system of Ca-HA-Fe aggregates and adsorption of the quaternary system of Ca-HA-Fe-Pb/Cu/Cd. In this study, interactions between Ca-HA-Fe ternary and Ca-HA-Fe-Pb/Cu/Cd quaternary systems were discussed from a molecular perspective. The structures of the basic structural units of HA were identified. Density functional theory (DFT) was employed to calculate the stable states of basic structural units of HA and Ca2+. The results showed that hydroxyl and carboxyl groups exhibited the highest capacity to bind with Ca2+. The interactions among Ca, HA, and Fe led to the formation of network aggregates. The binding energies of functional groups for heavy metals and the feasibility of ion exchange were calculated by the method of experiment and DFT. According to the contribution of functional group complexation and ion exchange, the ion exchange values for Pb2+, Cu2+, and Cd2+ were 66.71%, 62.87%, and 60.79%, respectively, which indicated that Ca2+ ion exchange showed considerable potential in enhancing the adsorption capacity of heavy metals.

Influence of low-cost Thai leucoxene minerals on the growth, bioactive compounds, and antibacterial activities of Chrysanthemum indium L. cuttings in in vitro culture

The effects of low-cost Thai leucoxene mineral (LM) at different concentrations (10, 20, 30, 40, 50, and 60 mg/L) on the growth and antibacterial properties of Chrysanthemum indium L. cuttings under in vitro were evaluated. The primary chemical composition of LM was approximately 86% titanium dioxide (TiO2), as determined by dispersive X-ray spectroscopy. The crystalline structure, shape, and size were investigated by X-ray diffraction and scanning electron microscopy. LM at 40 and 50 mg/L significantly increased plant height, leaf number, node number, and fresh and dry weight. These growth-promoting properties were accompanied by improved chlorophyll and carotenoid contents and antioxidant enzyme activities and reduced malondialdehyde levels. Additionally, LM treatment at 40 and 50 mg/L had positive effects on antibacterial activity, as indicated by the lowest minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values. The high levels of phenolic compounds in the plants contributed to the MIC and MBC values. In conclusion, these findings provide evidence for the effectiveness of LM in enhancing the growth of Chrysanthemum plants in in vitro culture and improving their antibacterial abilities.

Eco-friendly natural mineral biotite as a cesium adsorbent: Utilizing low-concentration acid and hydrogen peroxide

Biotite, a phyllosilicate mineral, possesses significant potential for cesium (Cs) adsorption owing to its negative surface charge, specific surface area (SSA), and frayed edge sites (FES). Notably, FES are known to play an important role in the adsorption of Cs. The objectives of this study were to investigate the Cs adsorption capacity and behavior of artificially weathered biotite and identify mineralogical characteristics for the development of an eco-friendly geologically-based Cs adsorbent. Through various analyses, it was confirmed that the FES of biotite was mainly formed by mineral structural distortion during artificial weathering. The Cs adsorption capacity is improved by approximately 39% (from 20.53 to 28.63 mg g-1) when FES are formed in biotite through artificial weathering using a low-concentration acidic solution mixed with hydrogen peroxide (H2O2). Especially, the Cs selectivity in Cs-containing seawater, including high concentrations of cations and organic matter, was significantly enhanced from 203.2 to 1707.6 mL g-1, an increase in removal efficiency from 49.5 to 89.2%. These results indicate that FES of artificially weathered biotite play an essential role in Cs adsorption. Therefore, this simple and economical weathering method, which uses a low-concentration acidic solution mixed with H2O2, can be applied to natural minerals for use as Cs adsorbents.

Oxidant-mediated radical reactions of the azole fungicide TEB in aquatic media: Degradation mechanism and toxicity evolution

The degradation of tebuconazole (TEB) by UV/H2O2, UV/NaClO, and ozonation was investigated in this research. The experimental findings unveiled that under the specified conditions, the degradation percentages of TEB were raised to 99% within 40 s, 5 min, and 3 min for UV/H2O2, UV/NaClO and ozonation, respectively. The mineralization percentages within 1 h were 59%, 31% and 8% for the three AOPs. UV/H2O2 and UV/NaClO technologies mainly acted through OH·, while O3 treatment primarily relied on the free radicals such as 1O2 and O2·-. UV-based AOPs achieved almost complete dechlorination within 1 h, whereas O3 treatment had a less effective dechlorination, reaching only 27.61%. Notably, UV alone achieved a dechlorination percentage of 43.07%. By identifying the TPs, we found that the three AOPs shared three similar degradation pathways. The degradation mechanism of TEB mainly entailed the removal of the benzene ring, tert-butyl group and triazolyl group. Toxicity assessment revealed an initial increase followed by a gradual decrease in toxicity for UV/NaClO and O3 treatments, whereas UV/H2O2 treatment exhibited a sustained decrease. This was due to the presence of TP278 and TP303 by UV/NaClO and TP168 and TP153 by ozonation. After estimating the costs of the three AOPs, UV/H2O2 standed out as the best choice for achieving a 90% degradation percentage and exhibiting lower toxicity performance, while O3 treatment was favored for low TOC demands. These research findings provided valuable reference for understanding the degradation mechanism and developing a new technology of the removal of TEB.

Innovations in textile wastewater management: a review of zero liquid discharge technology

Zero liquid discharge (ZLD) technology emerges as a transformative solution for sustainable wastewater management in the textile industry, emphasizing water recycling and discharge minimization. This review comprehensively explores ZLD's pivotal role in reshaping wastewater management practices within the textile sector. With a primary focus on water recycling and minimized discharge, the review thoroughly examines the economic and environmental dimensions of ZLD. Additionally, it includes a comparative cost analysis against conventional wastewater treatment methods and offers a comprehensive outlook on the global ZLD market. Presently valued at US $0.71 billion, the market is anticipated to reach US $1.76 billion by 2026, reflecting a robust annual growth rate of 12.6%. Despite ZLD's efficiency in wastewater recovery, environmental challenges, such as heightened greenhouse gas emissions, increased carbon footprint, elevated energy consumption, and chemical usage, are discussed. Methodologies employed in this review involve an extensive analysis of existing literature, empirical data, and case studies on ZLD implementation in the textile industry worldwide. While acknowledging existing adoption barriers, the review underscores ZLD's potential to guide the textile industry toward a more sustainable and environmentally responsible future.

Fixed-bed adsorption studies of endocrine-disrupting compounds from water by using novel calcium-based metal-organic frameworks

The presence of emerging water pollutants such as endocrine-disrupting compounds (EDCs), including 17-ethynylestradiol (EE2), bisphenol A (BPA), and perfluorooctanoic acid (PFOA), in contaminated water sources poses significant environmental and health challenges. This study aims to address this issue by investigating the efficiency of novel calcium-based metal-organic frameworks, known as mixed-linker calcium-based metal-organic frameworks (Ca-MIX), in adsorbing these endocrine-disrupting compounds. This study analyzed the influence of influent concentration, bed height, and flow rate on pollutant removal, with bed height emerging as a crucial factor. From the breakthrough curves, it was determined that the column maximum adsorption capacities followed the order of 17-ethynylestradiol (101.52 μg/g; 40%) > bisphenol A (99.07 μg/g; 39%) > perfluorooctanoic acid (81.28 μg/g; 32%). Three models were used to predict the adsorption process, with the Yan model outperforming the other models. This suggests the potential of mixed-linker calcium-based metal-organic frameworks for removing endocrine-disrupting compounds from water, using the Yan model as an effective predictor. Overall, this study provides valuable insights for the development of effective water treatment methods using mixed-linker calcium-based metal-organic frameworks to remove endocrine-disrupting compounds from contaminated water sources.

Robust iron-doped manganese oxide nanoparticles from facile fabrication to photo-catalytic degradation application of binary dyes mixture

The manganese oxide (MnO2 and iron-doped manganese oxide (Fe-MnO2) nanoparticles (NPs) with reduced band gap (Eg) were fabricated through the co-precipitation process. They used to degrade Indigo Carmine (IC) and Rhodamine B (RB) binary mixture in an aqueous medium under solar light irradiation. From FT-IR, the twisting modes of the Mn-O bond and the stretching vibrations of the Fe-Mn-O2 bond were confirmed from the peaks observed at 480 cm-1,584 cm-1,675 cm-1, and 900 cm-1, 1150 cm-1, and 1200 cm-1 respectively. The MnO2 has an optical band gap of 3.2 eV, which was decreased to 3 eV in Fe-MnO2. The zero charge (PZC) point was 8 for Fe-MnO2 and 7 for MnO2. The BET surface area for Fe-MnO2 was 398 m2/g, relatively higher than MnO2 particles, having a surface area of 384 m2/g. The average crystallite sizes calculated from Scherer formulae were 37 nm for MnO2 and 31 nm for Fe-MnO2 NPs. SEM confirmed the irregular morphology of the prepared particles. It was analyzed that agglomeration occurs in MnO2 than the Fe-MnO2. The maximum degradation of IC dye was 99%, and that of RB was 98% at the optimum conditions. The data were best fitted to second-order kinetics.

Olive stone as an eco-friendly bio-adsorbent for elimination of methylene blue dye from industrial wastewater

Adsorbents synthesized by activation and nanoparticle surface modifications are expensive and might pose health and ecological risks. Therefore, the interest in raw waste biomass materials as adsorbents is growing. In batch studies, an inexpensive and effective adsorbent is developed from raw olive stone (OS) to remove methylene blue (MB) from an aqueous solution. The OS adsorbent is characterized using scanning electron microscopy (SEM), Fourier Transform Infra-Red (FTIR), and Brunauer-Emmett-Teller (BET) surface area. Four isotherms are used to fit equilibrium adsorption data, and four kinetic models are used to simulate kinetic adsorption behavior. The obtained BET surface area is 0.9 m2 g-1, and the SEM analysis reveals significant pores in the OS sample that might facilitate the uptake of heavy compounds. The Langmuir and Temkin isotherm models best represent the adsorbtion of MB on the OS, with a maximum monolayer adsorption capacity of 44.5 mg g-1. The best dye color removal efficiency by the OS is 93.65% from an aqueous solution of 20 ppm at the OS doses of 0.2 g for 90 min contact time. The OS adsorbent serves in five successive adsorption cycles after a simple filtration-washing-drying process, maintaining MB removal efficiency of 91, 85, 80, and 78% in cycles 2, 3, 4, and 5, respectively. The pseudo second-order model is the best model to represent the adsorption process dynamics. Indeed, the pseudo second-order and the Elovich models are the most appropriate kinetic models, according to the correlation coefficient (R2) values (1.0 and 0.935, respectively) derived from the four kinetic models. The parameters of the surface adsorption are also predicted based on the mass transfer models of intra-particle diffusion and Bangham and Burt. According to the thermodynamic analysis, dye adsorption by the OS is endothermic and spontaneous. As a result, the OS material offers an efficient adsorbent for MB removal from wastewater that is less expensive, more ecologically friendly, and economically viable.

Effective adsorption of Pb(II) ion from aqueous solution onto ZSM-5 zeolite synthesized from Vietnamese bentonite clay

ZSM-5 zeolite was successfully synthesized from bentonite clay sourced from Lam Dong Province, Vietnam, using the hydrothermal method at 170 °C for 18 h. The synthesized ZSM-5 (SiO2/Al2O3 ratio ~ 34) exhibited a single phase with high crystallinity (91.8%), and a clear and uniform shape. In a detailed examination of the synthesized material's Pb(II) adsorptive capacity, various factors were taken into account, including pH, interaction time, ionic strength, and the amount of adsorbent. Isotherms and kinetics were examined to elucidate the uptake behavior. Study results suggested that Pb(II) ion uptake by ZSM-5 was most appropriately described by the Sips isotherm and intraparticle diffusion kinetic models. The calculated maximum monolayer adsorption capacity according to the Langmuir isotherm model was 48.36 mg/g. Furthermore, the adsorption mechanisms of Pb(II) on ZSM-5 involving electrostatic interactions, ion exchange, and diffusion into pores were demonstrated using the analytical techniques before and after Pb(II) adsorption. These findings demonstrate that ZSM-5 synthesized from bentonite clay exhibits an excellent adsorption capacity for Pb(II), resulting in promising applications for treating drinking water or aqueous industrial waste containing Pb(II) ions.

Adsorption characteristics of SO2 onto novel activated carbon fixed bed: kinetics, isotherms, thermodynamics and washing regeneration

The problem of SO2 pollution in industrial flue gas has brought great pressure to environmental governance. In this study, a new type of activated carbon fixed bed device was designed and built for flue gas desulfurization. The results showed that activated carbons (AC1-AC5) were microporous activated carbons with abundant functional groups on the surface, and the desulfurization performance was ranked as AC1 > AC2 > AC3 > AC4 > AC5. The specific surface area of AC1 was as high as 624.98 m2/g, and the maximum adsorption capacity was 29.03 mg·g-1 under the optimum reaction conditions. The Freundlich adsorption isotherm model and Bangham pore diffusion model are more suitable for describing the dynamic adsorption process of SO2 on AC1. Combined with thermodynamic research, it is shown that the adsorption process of SO2 is a spontaneous, exothermic, and chaotic reduction process, which is mainly a physical adsorption between single-layer adsorption and multi-layer adsorption. Finally, the desulfurization-washing regeneration cycle experiment results showed that the regeneration rate of AC1 increases with the washing time and washing temperature, up to 95%, which provides data reference for industrial application.

In Situ Synthesis of Doped Bio-Graphenes as Effective Metal-Free Catalysts in Removal of Antibiotics: Effect of Natural Precursor on Doping, Morphology, and Catalytic Activity

Wastewater contaminated with antibiotics is a major environmental challenge. The oxidation process is one of the most common and effective ways to remove these pollutants. The use of metal-free, green, and inexpensive catalysts can be a good alternative to metal-containing photocatalysts in environmental applications. We developed here the green synthesis of bio-graphenes by using natural precursors (Xanthan, Chitosan, Boswellia, Tragacanth). The use of these precursors can act as templates to create 3D doped graphene structures with special morphology. Also, this method is a simple method for in situ synthesis of doped graphenes. The elements present in the natural biopolymers (N) and other elements in the natural composition (P, S) are easily placed in the graphene structure and improve the catalytic activity due to the structural defects, surface charges, increased electron transfers, and high absorption. The results have shown that the hollow cubic Chitosan-derived graphene has shown the best performance due to the doping of N, S, and P. The Boswellia-derived graphene shows the highest surface area but a lower catalytic performance, which indicates the more effective role of doping in the catalytic activity. In this mechanism, O2 dissolved in water absorbs onto the positively charged C adjacent to N dopants to create oxygenated radicals, which enables the degradation of antibiotic molecules. Light irradiation increases the amount of radicals and rate of antibiotic removal.

Comparison of pesticide adsorption efficiencies of zeolites and zeolite-carbon composites and their regeneration possibilities

The presence of pesticides in our environment is a consequence of intensive industrial and civilizational development, necessitating the search for effective and safe methods to remove them. We suggest utilizing zeolite X and a zeolite-carbon composite, obtained through the chemical transformation of fly ash, as pesticide sorbents. To increase the sorption efficiency of 2,4-dichlorophenoxyacetic acid (2,4-D), 2-methyl-4-chlorophenoxyacetic acid (MCPA), carbendazim, and simazine, we functionalized the zeolite materials with cationic (hexadecyltrimethylammonium) and nonionic (Triton X-100) surfactants. We used transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric/differential thermal analysis (TG/DTA) and point of zero charge (pHpzc) analysis to characterize the functionalized sorbent materials. Our results indicate that cationic surfactants significantly enhance the adsorption of 2,4-D and MCPA. In contrast, carbendazim and simazine exhibit maximum sorption on the unmodified zeolite-carbon composite. The sorption mechanism is intricate, with physical sorption predominating, primarily due to electrostatic interactions between the protonated binding sites of the adsorbents and the negatively charged pesticide molecules. Regeneration tests demonstrated that ethanol is the most effective in regenerating zeolite-carbon composite with adsorbed MCPA and 2,4-D, while thermal regeneration was not possible. Adsorbents with simazine and carbendazim can be regenerated using both thermal and ethanol methods, but the thermal regeneration of zeolite with adsorbed simazine is more efficient. Utilizing functionalized zeolite materials obtained from industrial waste, such as fly ash, could provide an efficient way to remove pesticides from the environment.

Toward systematic understanding of adsorptive removal of legacy and emerging per-and polyfluoroalkyl substances (PFASs) by various activated carbons (ACs)

Per-and polyfluoroalkyl substances (PFASs) have received great attention due to their persistence, bioaccumulation and toxicity. Various activated carbons (ACs) exhibit wide variability in adsorptive performance towards PFASs. In order to gain a systematic understanding of adsorptive removal of legacy and emerging PFASs by ACs, the adsorption of ten PFASs on various ACs was comprehensively investigated. Results showed that granular activated carbon-1 (GAC-1) and powdered activated carbon-1 (PAC-1) removed more than 90% of all target PFASs. Particle size, surface charge, and micropores quantity of ACs were closely related to their performance for PFASs removal. Electrostatic interaction, hydrophobic interaction, surface complexation and hydrogen bonding were the adsorption mechanisms, with hydrophobic interaction being the predominant adsorptive force. Physical and chemical adsorption were both involved in PFAS adsorption. The removal rates of PFASs by GAC-1 decreased from 93%-100% to 15%-66% in the presence of 5 mg/L fulvic acid (FA). GAC was able to remove more PFASs under acidic medium, whereas PAC removed hydrophobic PFASs better under the neutral medium. The removal rates of PFASs by GAC-3 increased significantly from 0%-21% to 52%-97% after being impregnated with benzalkonium chlorides (BACs), demonstrating the superiority of this modification method. Overall, this study provided theoretical support for removing PFASs from water phase with ACs.

Adsorptive removal of malachite green dye from aqueous solution using Rumex abyssinicus derived activated carbon

The potential for malachite green dye saturated effluent to severely affect the environment and human health has prompted the search for effective treatment technologies. Thus, this study was conducted with the goal of developing activated carbon from Rumex abyssinicus for the adsorptive removal of malachite green dye from an aqueous solution. Unit operations such as drying, size reduction, impregnation with H3PO4, and thermal activation were used during the preparation of the activated carbon. An experiment was designed considering four main variables at their respective three levels: initial dye concentration (50, 100, and 150 mg/L), pH (3, 6, and 9), contact period (20, 40, and 60 min), and adsorbent dosage (0.05, 0.01, and 0.15 g/100 mL). Optimization of the batch adsorption process was carried out using the Response Surface methodology's Box Behnken approach. The characterization of the activated carbon was described by SEM for surface morphology with cracks and highly porous morphology, FTIR for multi-functional groups O-H at 3506.74 cm-1 and 3290.70 cm-1, carbonyl group stretching from aldehyde and ketone (1900-1700 cm-1), stretching motion of aromatic ring C=C (1543.12 cm-1), stretching motion of -C-H (1500-1200 cm-1), vibrational and stretching motion of -OH (1250.79 cm-1), and vibrational motion of C-O-C (1049.32 cm-1), pHpzc of 5.1, BET for the specific surface area of 962.3 m2/g, and XRD for the presence of amorphous structure. The maximum and minimum dye removal efficiencies of 99.9% and 62.4% were observed at their respective experimental conditions of (100 mg/L, 0.10 mg/100 mL, pH 6, and 40 min) and (100 mg/L, 0.15 mg/100 mL, pH 3, and 20 min), respectively. Langmuir, Freundlich, Toth, and Koble-Corrigan models were used to evaluate the experimental data, in which Koble-Corrigan model was found to be the best fit with the highest value of R2 0.998. In addition to this, the kinetic studies were undertaken using pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Boyd models, and as a result, the pseudo-second-order model proved to have a better fit among the kinetic models. The kinetics and isotherm analysis revealed that the nature of the adsorption to be homogenous and monolayer surfaces driven by chemosorption. Furthermore, the thermodynamics study revealed the nature of adsorption to be feasible, spontaneous, and endothermic. On the other hand, the reusability study depicted the fact that the adsorbent can be utilized for five cycles with a negligible drop in the removal efficiencies from 99.9 to 95.2%. Finally, the low-cost, environmentally benign, and high adsorption capacity of the adsorbent material derived from Rumex abyssinicus stem could be used to treat industrial effluents.

As(V) adsorption by FeOOH@coal gangue composite from aqueous solution: performance and mechanisms

Arsenic (As) pollution in water poses a significant threat to the ecological environment and human health. Meanwhile, the resource utilisation of coal gangue is of utmost importance in ecologically sustainable development. Thus, the FeOOH@coal gangue composite (FeOOH@CG) was synthesised for As(V) adsorption in this study. The results showed that α-FeOOH, β-FeOOH and Schwertmannite loaded on the surface of FeOOH@CG. Moreover, the adsorption behaviour of As(V) by FeOOH@CG was investigated under different reaction conditions, such as pH, contact time, initial concentration and co-existing anions. The optimum adsorption conditions were as follows: initial As(V) concentration of 60 mg/L, pH of 3.0 and adsorption time of 180-240 h. The adsorption capacity of FeOOH@CG for As(V) was pH-dependent and the maximum adsorption capacity was 185.94 mg/g. The presence of anions (H 2 PO 4 - , HCO 3 - and C l - ) decreased the adsorption efficiency of FeOOH@CG for As(V). The adsorption process of FeOOH@CG for As(V) could be well-described by the pseudo-second-order model and Langmuir model, indicating that the adsorption process mainly depended on chemical adsorption. The thermodynamic analysis suggested that the adsorption was a spontaneous and endothermic process. In addition, according to the analyses of XRD, FTIR and XPS, the dominant mechanisms of As(V) adsorption by FeOOH@CG were electrostatic attraction, complexation and precipitation. In conclusion, FeOOH@CG has great potential as an efficient and environmentally friendly adsorbent for As(V) adsorption from aqueous solution.

Photosensitization of TiO2 microspheres by novel Quinazoline-derivative as visible-light-harvesting antenna for enhanced Rhodamine B photodegradation

Water pollution is one of the global threats severely affecting our planet and human health. Organic textile dyes are one of the common organic water pollutants that are presentient to degradation by traditional physical methods. Semiconductor-assisted photocatalysis is considered a green, efficient, and sustainable technology for wastewater treatment. To maximize the efficient utilization of solar radiation, it is of pivotal significance to explore novel organic molecules to be employed as efficient dye sensitizers for wide-bandgap semiconductors to extend their performance to the Visible-light region. Hence, in this work, we are proposing the design and synthesis of novel structures of QAD molecule as a dye photosensitizer with extended visible light absorptivity due to the extended π-π/n-π conjugations, to promote the performance of TiO2 nanoparticles to the visible-light region and enhance the charge separation. The physicochemical characterizations confirmed the successful synthesis of QAD, TiO2, and QAD/TiO2 samples with the proposed structures. The anchoring of QAD molecules on the surface of TiO2 caused a substantial improvement in the optical characteristics of TiO2 as well as overcoming its common drawbacks by decreasing its bandgap energy to 2.6 eV, a remarkable reduction of PL intensity indicating reducing the e-h recombination and enhancing the charge separation, and creation of efficient visible light-harvesting antenna in the range of 400-600 nm. Besides, the QAD/TiO2 sample achieved a 3-fold enhancement in the observed rate constant of the photodegradation of Rhodamine B dye compared to the bare TiO2. The parameters affecting the photodegradation process were optimized and the sample displayed outstanding stability after 4 consecutive cycles. Finally, the effect of the scavengers was investigated and [Formula: see text] was proposed to be the most reactive species and the mechanism of the enhancement was suggested based on the electron injection from the QAD's HOMO level to the TiO2's CB. Finally, this work opens the door for various studies for the investigation of the proposed structures or similar structures in various photocatalytic/biomedical applications.

Evaluation of the effectiveness of amendments derived from vermicompost combined with modified shell powder on Cd immobilization in Cd-contaminated soil by multiscale experiments

The widespread heavy metal contamination of agricultural soils poses an enormous challenge to food safety. To evaluate the Cd immobilization potential of vermicompost combined with modified shell powder (VMSP) on Cd-contaminated soil, batch adsorption tests and field experiments were conducted. First, the Cd²⁺ removal characteristics and adsorption mechanisms of vermicompost (V), vermicompost combined with shell powder (VSP), and VMSP in an aqueous solution were investigated by batch tests. Then, 3 kg·m² V, VSP, and VMSP doses were applied to Cd-contaminated farmland soils as soil amendments to plant green garlic (Allium sativum L.) and investigate their Cd immobilization effects in Cd-contaminated soils. Batch adsorption tests showed that VMSP was most effective for Cd²⁺ removal, with adsorption rates as high as 85.7-99.79% and desorption rates of approximately 1.25-1.34%. Combining further characterization analysis of VMSP, it was demonstrated that the adsorption mechanism of Cd²⁺ was monolayer chemisorption, mainly involving the complexation reaction of Cd²⁺ with organic functional groups and the precipitation reaction of Cd²⁺ with mineral elements. The field experiment showed that adding V, VSP, and VMSP effectively inhibited the enrichment of Cd in green garlic, and the Cd content was reduced by 42.18%, 46.88%, and 68.75%, respectively. However, only the Cd content of green garlic treated with VMSP was lower than the national standard for food safety in China (Cd≤ 0.2 mg·kg^-1). V, VSP, and VMSP additions improved soil fertility and reduced Cd bioavailability in the soil by 15.5%, 18.9%, and 36.3%, respectively. In addition, V, VSP, and VMSP addition increased bacterial diversity and improved bacterial communities and functions in the soil by improving basic soil properties and reducing Cd-related toxicity. The results indicated that VMSP is a promising amendment for Cd immobilization in Cd-contaminated farmland soils.

Applying MCM-48 mesoporous material, equilibrium, isotherm, and mechanism for the effective adsorption of 4-nitroaniline from wastewater

In this work, the MCM-48 mesoporous material was prepared and characterized to apply it as an active adsorbent for the adsorption of 4-nitroaniline (4-Nitrobenzenamine) from wastewater. The MCM-48 characterizations were specified by implementing various techniques such as; scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, pore size distribution (PSD), and Fourier transform infrared (FTIR). The batch adsorption results showed that the MCM-48 was very active for the 4-nitroaniline adsorption from wastewater. The adsorption equilibrium results were analyzed by applying isotherms like Langmuir, Freundlich, and Temkin. The maximum experimental uptake according to type I Langmuir adsorption was found to be 90 mg g^-1 approximately. The Langmuir model with determination coefficient R² = 0.9965 is superior than the Freundlich model R² = 0.99628 and Temkin model R² = 0.9834. The kinetic adsorption was investigated according to pseudo 1st order, pseudo 2nd order, and Intraparticle diffusion model. The kinetic results demonstrated that the regression coefficients are so high R² = 0.9949, that mean the pseudo 2nd order hypothesis for the adsorption mechanism process appears to be well-supported. The findings of adsorption isotherms and kinetics studies indicate the adsorption mechanism is a chemisorption and physical adsorption process.

Critical parameters influencing the continuous performance of upflow microbubble airlift photocatalytic process treating pharmaceutical pollutants

The advances in heterogeneous photocatalysts are still confined to evaluating the functional photocatalytic activity of catalysts in simple batch-mode operation. Nevertheless, the long-term stability, recovery-reusability, and cost-effectiveness of photocatalysts are critical issues in practical applications for pollution control. This study examined the critical parameters to improve the photocatalytic degradation activity of the antibiotic tetracycline and strategized successful continuous performance in a two-stage photocatalytic process adopting sequencing batch-mode microbubble upflow airlift reactor (UALR) followed by the centrifugal separation of CdS nanoparticles (NPs). The most effective strategy for NPs separation was a sequential combination of gravity separation (10 min settling) in the settling phase and subsequent high-speed centrifugation (5 min at 25,000×g) of the settled NPs sediments, providing an economic benefit by reducing the centrifugation capacity. During steady state operation under the optimal conditions, the UALR showed reliable performance, resulting in 97-91% and 85-81% degradation efficiency at 60- and 30-min reaction time per cycle, respectively. A weak basic condition (pH 8) and dissolved oxygen (DO) supplementation increased the photocatalytic activity by 12% (0.0292 min^-1) and 30% (0.0363 min^-1) compared to the control. Trapping studies confirmed the enhanced performance using various reactive oxygen species scavengers, revealing an increase in ^•OH generation (6.5%).

Adsorption of crystal violet on activated bamboo fiber powder from water: preparation, characterization, kinetics and isotherms

Biomass-activated carbon has made a great contribution as an adsorbent in the field of dye wastewater treatment. In this study, the response surface method (RSM) based on the Box-Behnken design was used to optimize the preparation process. Bamboo fiber activated carbon (BAC) with a specific surface area of 2892 m² g^-1 and a pore volume of 1.80 cm³ g^-1 was prepared. Various characterization methods (SEM, XPS, XRD, and Raman spectroscopy) were used to analyze the micro-structure of BAC. In the microscopic state, the BAC is fibrous and maintains the originally connected pores of the bamboo fiber. After high-temperature activation, the microcrystallinity of BAC decreases, and the degree of graphitization is low, indicating the presence of amorphous carbon. The adsorption capacity of BAC to crystal violet in simulated wastewater was evaluated via an adsorption experiment. Under the following conditions: the dosage of BAC was 0.04 g, the concentration was 600 mg L^-1, the adsorption temperature and time were 25 °C and 30 min, respectively, and the as-prepared BAC had a 99.96% removal rate. The adsorption process conformed to the pseudo-second-order kinetic model and Langmuir adsorption isotherm model, indicating that the adsorption process of CV on BAC belonged to monomolecular layer adsorption. The adsorption process occurs spontaneously and is accompanied by heat release, and the maximum adsorption capacity of BAC within a given concentration range could reach 1353.09 mg g^-1. SEM-EDS characterization before and after adsorption showed that ion exchange and the presence of oxygen-containing functional groups played an important role in promoting the adsorption process. The results show that BAC considerably affects CV removal, which has great application prospects.