Pseudo-first Order Kinetic Equation Research Articles

Zero-valent iron on graphite-cellulose biochar catalysts for the Fenton degradation of tetracycline from water

Tetracycline (TC), an antibiotic widely used in the treatment of animal and human diseases and promotion of animal growth. However, its uncontrolled discharge to water sources can also cause the promotion of antibiotic resistant bacteria and genes. In this study, graphite and cellulose were used as raw materials to construct a graphite-biochar (G-BC) by carbothermal reactions. This graphite-biochar was subsequently mixed with ZVI with various mass ratios by ball milling to produce graphite-biochars supported ZVI (ZVI/G-BC) catalysts, further used in the heterogeneous Fenton degradation of tetracycline. The materials were fully characterized by different techniques. The removal of TC by BC, G-BC and ZVI/G-BC was tested under different reaction conditions. The best synthesis conditions were achieved at a heating temperature of 700 °C, a graphite content of 20 %, a ball milling speed of 500 rpm, a ball milling time of 5 h, as well as a G-BC and ZVI mass ratio of 1:3. Graphite improves the conductivity and micropore area of the material, which enhances the removal of TC by ZVI/G-BC catalysts in Fenton-like reactions. TC was first oxidized to intermediate products and then further mineralized to CO2 and H2O. The best TC removal performance was obtained with a catalyst dosage of 1.1 g·L1, a hydrogen peroxide concentration of 140 mM and an initial pH value of 3. The reaction data fitted properly a pseudo first-order kinetic equation. TC removal as high as 91 % was achieved even in the 3rd round of reuse. This study reports a novel ZVI material with high conductivity and good TC removal performance.

Effective photocatalytic degradation of sulfamethoxazole using PAN/SrTiO3 nanofibers

Freshwater scarcity driven by pollution and climate change necessitates the development of effective water purification methods. There is an urgent need for innovative solutions that can efficiently remove contaminants from water sources. A effective material for the photocatalytic degradation of organic sulfonamide antibiotics from water was developed in this study. A composite of electrospun strontium titanate (SrTiO3) and carbon fibers polyacrylonitrile/strontium titanate (PAN/SrTiO3) was employed for the photocatalytic degradation of sulfamethoxazole (SMX). Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM-EDS), Transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterise the composite. The fibers had a thickness of ~250 nm and uniformly dispersed PAN and SrTiO3 particles. A PAN/SrTiO3 composite with a 1:1 mass ratio (20 mg) demonstrated excellent performance, achieving over 90 % degradation at pH 7 and a contaminant concentration of 5 mg/L under ultraviolet (UV) light irradiation during 60 min. The composite was tested for the photodegradation of the major organic pollutant (SMX) in distilled and river water. In river water, the degradation efficiency exceeded 80 % at pH 7 because of the formation of secondary radicals involved in antibiotic degradation. SMX degradation was described using a pseudo-first order kinetic equation using the Langmuir-Hinshelwood model. These results underscore the novelty and significance of the PAN/SrTiO3 composite and demonstrate its high efficiency and potential for large-scale water purification applications.

Simple and modified chitosan gel beads from a natural source as a bio-sorbent for water defluoridation: Experimental and computational perspectives

Water contaminated with fluoride (F -) is widely acknowledged as a major global issue that poses serious health and environmental risks. Adsorption is one of the many fluoride removal treatment methods that has been widely and successfully investigated. In this work, we describe a simple process for making both cross-linked and uncross-linked chitosan gel beads from shrimp waste. SEM, FTIR, XRD and TGA analysis confirmed the successful synthesis of the non-cross-linked chitosan gel beads (Cs beads) and cross-linked chitosan gel (Cs-Ech beads) whose swelling behavior, stability and fluoride removal efficiency were studied. The adsorption conditions were also optimised. An adsorption capacity of 16.59 mg/g was achieved after just 30 min and at pH = 6.8, 10 mg/L and T = 25 °C. It was shown that chitosan gel beads cross-linked with epichlorohydrin removed more fluoride than non-cross-linked chitosan gel beads. The rate of adsorption of fluoride ions is determined by the pseudo-first order kinetic equation. On the other hand, equilibrium data was best described by Langmuir adsorption isotherms. Density functional theory calculations (DFT) based on quantitative analyses were used to explore the interfacial interaction mechanisms, offering valuable perspectives on the inter- and intra-molecular interactions. Further studies on weak interaction were conducted, focusing on the binding contribution of electrostatic interaction and vdW potential. DFT results confirmed the strong adsorption capacity and coordination behavior of F - ions on the cross-linked Cs-Ech, suggesting that the Ech group offers preferred adsorption sites.

Sustainable conversion of polyethylene plastic bottles into terephthalic acid, synthesis of coated MIL-101 metal–organic framework and catalytic degradation of pollutant dyes

Persistent environmental colored compounds, resistant to biodegradation, accumulate and harm eco-systems. Developing effective methods to break down these pollutants is crucial. This study introduces Ag-MIL-101 (Ag-MIL-101) as a composite and reusable catalyst that efficiently degrades specific colored organic pollutants (COPs) like Methylene blue (MB), 4-Nitrophenol (4-NP), and 4-Nitroaniline (4-NA) using sodium borohydride at room temperature. The MIL-101 was synthesized using Terephthalic acid (TPA) derived from the degradation of Polyethylene Terephthalate (PET) plastic waste, with the assistance of zinc chloride. To further investigation, the kinetics of degradation reaction was studied under optimized conditions in the presence of Ag-MIL-101 as catalyst. Our results demonstrated the remarkable efficiency of the degradation process, with over 93% degradation achieved within just 8 min. The catalyst was characterized using FTIR, XRD, FESEM, and TEM. In this study, the average particle size of Ag-MIL-101 was determined using SEM and XRD analysis. These methods allow us to accurately and precisely determine the particle size. We determined the reaction rate constants for the degradation of each COP using a pseudo first-order kinetic equation, with values of 0.585, 0.597 and 0.302 min−1 for MB, 4-NP, and 4-NA, respectively. We also evaluated the recyclability of the catalyst and found that it could be reused for up to three cycles with only a slight decrease in efficiency (10–15%). Overall, our findings highlight the promising application of Ag-MIL-101 as an effective catalyst for the degradation of COPs, emphasizing the importance of optimizing reaction conditions to achieve enhanced efficiency.

Precious metal-based Catalytic Membrane Reactors for continuous flow catalytic hydrodechlorination

This work is focused on the development of Catalytic Membrane Reactors (CMRs) comprising precious metals as active phases for a comparative assessment in continuous-flow catalytic hydrodechlorination (HDC). HDC has proved its remarkable potential for application as polishing step in drinking water treatment plants, but studies operating in continuous mode are scarce. Preliminary experiments were conducted in batch operation using Pd/Al2O3, Rh/Al2O3 and Pt/Al2O3 powder catalysts to evaluate the influence of the active phase on the removal of prochloraz (PCZ) (100 μg L−1), a pesticide listed on the EU Watch List (2022/1307), by HDC. PCZ removal was successfully described by a pseudo-first order kinetic equation and reaction pathways were proposed. Among the catalysts tested, Pt-based suffered a significant deactivation, not warranting the elimination of this micropollutant. Pd/Al2O3 exhibited a faster removal of PCZ than Rh/Al2O3, while this catalyst resulted in further hydrogenation of the non-chlorinated reaction product. Accordingly, different CMRs were developed by decorating cylindrical inert porous alumina membranes with Pd, Rh, and a combination of Pd-Rh as active phases (∼1% wt.). All CMRs showed a remarkable stability along 100 h on stream, being Pd/CMR be the most effective, with a pseudo-first order rate constant value of 0.062 min−1. An assessment of the impact of operating conditions (aqueous flow rate, PCZ initial concentration, temperature and H2 flow rate) was conducted using the Pd/CMR, which notably remained stable for 450 h on stream. The versatility of the system was finally demonstrated in tap water, achieving a steady-state PCZ conversion close to 95 %.

Sulu Çözeltide Tetrasiklin Giderimi için Fındık ve Antep Fıstığı Kabuklarının Eş-karbonizasyonundan Elde Edilen Yeni Hidrokömürün Kullanımı

In present work, the use of a new hydrochar (HSPSHC) produced by the combined hydrothermal carbonization (co-HTC) of hazelnut and pistachio shells (HS and PS) as a sorbent material in tetracycline (TC) antibiotic removal from water was investigated. It was obtained from hydrothermal carbonization of HSPSHC, hazelnut and pistachio shells by mixing 1:1 by mass at 220 oC for 6 h. Mass yield, energy density and higher heating value parameters were calculated for HSPSHC, and the surface chemistry was characterised using Fourier transform infrared spectroscopy (FTIR). TC adsorption on HSPSHC was carried out by kinetic and isotherm studies using batch method. The experimental kinetic results were qualified in pseudo first-order (PFO) and second-order (PSO) kinetic equations and it was observed that the adsorption complied with the PSO kinetics. The experimentally obtained results were applied to Langmuir and Freundlich model equations and isotherm modeling was performed. The adsorption isotherm of TC on the prepared hydrochar was well fitted by the Langmuir equation, which yielded a maximum monolayer adsorption capacity of TC of qm: 137.06 mg/g at 323 K and pH 4.0 on the HSPSHC hydrochar. In addition, thermodynamic studies revealed that the adsorption of TC by HSPSHC is spontaneous and is an endothermic process.

Leaf extract of Cimbopogan citratus supported CuO/ZnO nanocomposite and their applications in photocatalytic and antibacterial activities

We have focused on the green synthesis of copper oxide nanoparticles (CuONPs) and zinc oxide nanoparticles (ZnONPs) and CuO coated with ZnO nanocomposite (CuO/ZnO) by using leaf extract of Cimpobogan citrates (CC) as reducing and stabilizing agent. Copper sulfate pentahydrate (CuSO4.5H2O) and zinc acetate dihydrate (Zn(CH3COO)2.2H2O) are the forerunners in the hydrothermal synthesis. The prepared ZnONPs, CuONPs and CuO/ZnO nanocomposite were characterized using various instrument techniques such as Fourier Transform-Infrared spectroscopy (FT-IR), UV-visible spectroscopy (UV-Vis), X-ray diffraction pattern (XRD), Scanning electron microscope (SEM), Energy dispersive X-ray analysis (EDAX) and High Resolution-Transmission Electron microscope (HR-TEM). The results showed that the average size of CuO/ZnO nanocomposite was 20-50 nm. The Tauc plot of CuO/ZnO nanocomposite shows low band gap (1.56ev). Under visible light illumination, methylene blue (MB) was degraded photocatalytically using ZnONPs, CuONPs and CuO/ZnO nanocomposite which was then examined using UV-visible spectroscopy. In comparison to ZnONPs (65%) and CuONPs (80%), CuO/ZnO nanocomposite showed superior photocatalytic activity for the breakdown of MB with a high percentage degradation efficiency (85%). The photocatalytic degradation rate constant was evaluated by using a pseudo-first order kinetic equation. Additionally, the agar disc diffusion method was used to examine the antibacterial activity against two bacterial strains (Escherichia coli and Staphylococcus aureus) and a sizable zone of inhibition against the bacterial strains was found.

Application of catalytic hydrodechlorination for the fast removal of chlorinated azole pesticides in drinking water

Catalytic hydrodechlorination (HDC) is regarded as a promising purifying technology for drinking water treatment. So far, it has proved to be highly effective for the removal of different groups of chlorinated micropollutants including pharmaceuticals, neonicotinoid pesticides, personal care products or chloroacetic acids. The azole pesticides, recently included in the EU Watch Lists (Decisions 2020/1161 and 2022/1307), are a group of micropollutants of particular concern for drinking water given their high toxicity, persistence, and bioaccumulation potential. In this work, the feasibility of HDC for the removal of a representative group of chlorinated azole pesticides tebuconazole (TEB), tetraconazole (TET), prochloraz (PCZ), penconazole (PEN), metconazole (MET) and imazalil (IMZ)) is demonstrated, and their reactivity is compared with that observed for other halogenated micropollutant groups. Notably, all the pesticides investigated in this work (100 μg L−1) were completely dechlorinated within 30 min under ambient conditions using a 1 wt% Pd/Al2O3 catalyst concentration of 0.25 g L−1 and a H2 feeding of 50 mL N min−1. The experimental data were accurately described by a pseudo-first order kinetic equation and rate constant values in the range from 1.08 to 2.60 L gcat−1 min−1 were obtained. These values are quite close to those achieved for the most reactive neonicotinoid pesticides and significantly higher than the obtained for chloroacetic acids and most pharmaceuticals (e.g. diclofenac, sertraline or chlorpromazine). From the identification of the generated reaction intermediates and the final non-chlorinated products, sequential reaction pathways were proposed for each pollutant. Remarkably, despite the high toxicity exhibited by the azole pesticides tested, with LC50 values within the 0.4–7.0 mg L−1 range using A. salina, HDC effluents were non-toxic in all cases. Furthermore, the catalyst showed a remarkable stability upon three consecutive runs. Finally, the versatility of the process was demonstrated in the treatment of real aqueous matrices such as DWTP and tap water, where no significant differences were found either in terms of activity or stability.

Interfacial charge transfer of hybrid (Fe3+/Fe2+)/SnO2/TiO2 composites for highly efficient degradation of chromium (VI) under ultra-violet light illumination via Z-scheme

A series of heterostructures (Fe3+/Fe2+) incorporated on SnO2/TiO2, SnO2 and TiO2 were prepared by the photochemical reduction method in neat water and 30% PriOH in water as a solvent medium and were characterized. XPS analysis confirmed the reduced state of Fe3+/Fe2+ on composite materials and introduced new additional energy level to diminish the recombination rate of photo-generated electron-hole pairs to photocatalytic reaction. The synergistic effect of SnO2/(Fe3+/Fe2+)/TiO2 composites is more efficient in pH 3, and the presence of organic sacrificial reagents like EDTA and citric acid to trap centre of holes created on the catalyst surface to degrade the Cr(VI) ion. The photocatalytic reduction of potassium dichromate is described by the pseudo-first order kinetic equation. Ternary SnO2/(Fe3+/Fe2+)/TiO2 composites were speculated to accelerate the effective separation of electron-hole (e‒/h+) pairs, and enhanced the transportation rate of ecb− to the pollutants improved the photocatalytic activity than the (Fe3+/Fe2+)/SnO2 and (Fe3+/Fe2+)/TiO2 binary components.

Investigation on the adsorption desulfurization effect of carboxyl and phosphotungstic acid modified UiO-66

UiO-66 loading carboxyl and phosphotungstic acid has a good affinity to thiophene (TH). The synthesized catalyst, changed its original structure, which can increase its reactive site and enhance the interaction with thiophene (TH) in order to improve the adsorption performance. Then the structural changes were analyzed by XRD, FT-IR, SEM, BET, EDS and other characterization methods. Through static experiments of adsorption desulfurization, it is found that when the adsorption time is 240 min, the adsorption temperature is 30 ℃ and the oil-to-agent ratio is 100:1, the adsorption effect: UiO-66-(COOH)2 (UC2) > UiO-66, the highest adsorption capacity can reach 89.99 mg/g; while PTA@UiO-66 (PAU) can reach adsorption equilibrium at 210 min, it has better desulfurization performance than UiO-66. After being recycled for 5 times, the adsorption effect is only slightly decreased: the adsorption capacity of UC2 was still 78.02% of the initial adsorption capacity, while that of PAU was 76.07% of the initial adsorption capacity. According to the adsorption kinetics, the adsorption process of thiophene on the adsorbent UC2 is more consistent with W-M model, and the adsorption of PAU is more in line with the pseudo-first order kinetic equation. In addition, it also includes the process of intraparticle diffusion and liquid film diffusion.

Green synthesis of Ag nanoparticles using elm pod polysaccharide for catalysis and bacteriostasis

The green synthesis of silver nanoparticles (Ag NPs) for catalysis and biological applications has gained great interest. Natural elm pods are a type of food that possesses anti-inflammatory and pain-relieving effects. In this study, elm pod polysaccharide (EPP) was extracted from elm pods using hot water extraction for the first time. Biocompatible EPP-stabilized silver nanoparticles (EPP-Agn NPs) were prepared by using a green synthesis method. The EPP-Ag25 NPs had a hydrodynamic size of 40.9 nm and a highly negative surface charge of −27.4 mV. Furthermore, EPP-Ag25 NPs exhibited high catalytic activity for the reduction of 4-nitrophenol, and the catalytic reaction followed a pseudo-first order kinetic equation. More importantly, the inhibition rate of EPP-Ag25 NPs on Escherichia coli was 71 % when samples were treated with an 808 nm laser. Besides, EPP-Agn NPs effectively inhibited the proliferation of tumor cells irradiated by an 808 nm laser. The improved performance of EPP-Agn NPs was due to the good stability of EPP. Taken together, EPP-Agn NPs had good stability, catalytic activity, antibacterial and antitumor ability under laser irradiation. EPP is a good stabilizer for many nanoparticles which have broad applications in the field of catalysis and biomedicine in the future.

Accumulation, chemical speciation and ecological risks of heavy metals on expanded polystyrene microplastics in seawater

Expanded polystyrene (EPS) microplastics (MPs) have become a major component of plastic debris both on land and in marine systems globally. However, the accumulation and speciation distribution of heavy metals on EPS MPs and their potential hazards to marine organisms are still unknown. In this study, a 12-month field experiment investigating EPS exposure to seawater was conducted, and concentrations and speciation of six heavy metals (Cu, Zn, Cd, Pb, As, and Ni) on the EPS MPs were studied along with an evaluation of their ecological risks. Results showed that the accumulation of heavy metals on the EPS MPs increased over the exposure time, which conformed to a pseudo first-order kinetic equation. Speciation analysis suggested that Cu, Zn, Cd, and Ni principally distributed in the acid soluble fraction, while Pb and As primarily existed in the reducible fraction. There were significant correlations among the reducible fraction, the oxidizable fraction, the residual fraction, and the carbonyl index (p < 0.05). Compared with heavy metals in sediments, the migration and bioavailability of heavy metals on the aged EPS MPs were higher. By comprehensively considering the accumulation amount, chemical speciation and toxicity, the risk levels of heavy metals on the EPS MPs were in the decreasing orders of Cd > Pb > As > Ni > Cu > Zn. The ecological risk of heavy metals on the EPS MPs increased over the exposure time, and Cd, Pb, As, and Ni were the primary contributing factors. Our study results will be helpful for better understanding the ecological risk level of heavy metals on MPs, and will provide a reference for further research on the ecological toxicity of MPs.

Synthesis of 4-(benzyloxy)biphenyl under a multi-site phase-transfer catalyst along with ultrasonication – A kinetic study

In this present study, the synthesis of 4-(benzyloxy)biphenyl has been successfully carried out using 4-phenylphenol and benzyl chloride in the presence of ultrasonic power (40 kHz, 300W) along with synthesized multi - site phase - transfer catalyst viz., N1,N2-dibenzyl-N1,N1,N2,N2-tetramethylethane-1,2-diaminium dibromide (MPTC). The pseudo first-order kinetic equation has been applied to describe the organic reaction. The various kinetic parameters on the preparation of 4-(benzyloxy)biphenyl has been carried out under ultrasonic frequency condition and synthesized multi - site phase transfer catalyst. Sonication has resulted in better selectivity, high yield, avoids the use of the high temperature, side products and reduces the time consumption. The activation energy (Ea) has been calculated from the experimental results.

Fabrication of Epigallocatechin-3-gallate (EGCG) functionalized Mn3O4 for enhanced degradation of carbamazepine with peroxymonosulfate activation

Peroxymonosulfate activation via heterogeneous catalyst was broadly applied for the treatment of PPCPs. In this work, a novel material of Epigallocatechin-3-gallate (EGCG) fuctionalized Mn3O4 nano-octahedra (E@MO) was synthesized and utilized for the degradation of carbamazepine. Various technologies such as X-ray diffraction, Fourier transform-infrared spectroscopy, Scanning electron microscope, Transmission electron microscope, Brunauer-Emmett-Teller and X-ray photoelectron spectroscopy were employed for the characterization of the as-synthesized catalyst. The results depicted that under the conditions of CBZ concentration 5 mg/L, PMS concentration 1 mM, catalyst dosage 0.2 g/L, initial pH 5.8 and 25 °C, the targeted pollutant could be totally degraded in 60 min with a rate constant of 0.0622 min−1. When temperature raised to 45 °C, CBZ was removed completely in 20 min and the rate constant (0.1668 min−1) was 2.59 times than that of 25 °C, implying the degradation process was an endothermic reaction. Scavenging experiments and EPR analysis confirmed the main reactive oxygen species generated in the reaction were sulfate radical (SO4•) and hydroxyl radical (•OH), while SO4• serviced as the leading role. Due to the reduction property of EGCG, compared with bare Mn3O4, the CBZ degradation was markably enhanced and the degradation reaction were accurately matched with the pseudo first-order kinetics equation. The possible twelve intermediates produced in the decomposition of CBZ were identified by HPLC-MS/MS, their ecotoxicity were evaluated and compared by ECOSAR model. Together with the consequences, the degradation mechanism of CBZ in the E@MO/PMS system was propounded.

MOFs-derived magnetic hierarchically porous CoFe2O4-Co3O4 nanocomposite for interfacial radicals-induced catalysis to degrade chloramphenicol: Structure, performance and degradation pathway

Bimetallic organic frameworks derived bimetallic oxides as novel heterogeneous catalysts have been admitted to enhance catalytic capacity to great extent for peroxymonosulfate (PMS) activation. Herein, a magnetic hierarchically porous CoFe2O4-Co3O4 nanocomposite derived from heterometallic MIL-100 was one-step synthesized via manipulation of Fe/Co ratio and used to degrade chloramphenicol (CAP) in water. The structure of CoFe2O4-Co3O4 nanocomposite was evaluated by various characterization modes. The catalytic activity of CoFe2O4-Co3O4 nanocomposite was evaluated according to removal efficiency of CAP. Furthermore, the interfacial activation mechanism was deduced by a series of analysis. The results revealed CoFe2O4-Co3O4 nanocomposite was sphere-like nanoparticles with hierarchically micro/mesoporous structure. The nanocomposites had well-performed degradation efficiency toward 200 mL CAP of initial concentration of 10 mg/L (100% within 60 min). All of degradation followed the pseudo-first order kinetic reaction equation (kobs = 0.091 min−1). The whole degradation relied on interfacial radical generation via synergistic catalysis and sulfate radical (SO4•−) as well as hydroxyl radical (HO•) were ascertained as main reactive oxygen species (ROS). The possible degradation pathways involving dehydration, hydroxylation, substitution, oxidation, ring opening were proposed accordingly. This paper paid much attention to synergistic catalytic activity of Fe/Co and interfacial electron-transfer mechanism between CoFe2O4-Co3O4 nanocomposite and PMS, shedding a light on in-depth exploration of MOFs-derivates induced heterogeneous catalysis.

Fate of sulfamethoxazole and potential formation of haloacetic acids during chlorine disinfection process in aquaculture water

There exist two common processes in fishery culture, i.e. antibiotic addition to reduce disease in fishery, and chlorination disinfection to inhibit infectious pathogenic microorganisms. However, antibiotic residues might play important reverse side roles for both aquaculture water pollution and potential formation of chlorination side products. Herein, the transformation behaviour, intermediates analyses and conversion pathway of antibiotic sulfamethoxazole (SMX), and potential generation of halogenated acetic acids (HAAs) in the process of chlorination in fishery water were examined, and the results revealed that the decomposing of SMX satisfied a pseudo first-order kinetic equation. Both the addition of available chlorine and high temperature had affirmative influences on the decontamination of SMX and production of HAAs, and the near-neutral pHs promoted the removal of SMX and generation of HAAs. Br− was favorable for the removal of SMX and yields of brominated acetic acids (Br-AAs). Based on the identified intermediate products, the transformation path of SMX in chlorination process was propounded, to wit, the C–S and S–N bonds in the SMX molecules were firstly cracked, and the primeval intermediate groups are then transformed to form chloroanilines, chlorophenols, etc., and subsequently, chlorophenols were chlorinated and ring-opened to generate toxic HAAs. This study might be meaningful to evaluate the effective removal of sulfonamide antibiotic residues and the potential generation of halogenated DBPs (H-DBPs) when chlorinated in aquaculture water.

Highly efficient debromination of 4,4'-dibrominated diphenyl ether by organic palygorskite-supported Pd/Fe nanoparticles.

Organic palygorskite (OP)-supported Pd/Fe nanoparticles composite (OP-Pd/Fe) was prepared by stepwise reduction method. The removal capacity of 4,4'-dibrominated diphenyl ether (BDE15) by OP-Pd/Fe was compared with other various materials. For better understanding the possible mechanism, the synthesized and reacted OP-Pd/Fe materials were characterized by TEM, SEM, XRD, and XPS, respectively. The effects of major influencing parameters on the degradation of BDE15 were also studied. Benefit from the synergistic effect of the carrier and bimetallic nanoparticles, BDE15 could be completely debrominated into diphenyl ether (DE) under suitable conditions. A two-stage adsorption/debromination removal mechanism was proposed. The degradation of BDE15 with OP-Pd/Fe was mainly stepwise debromination reaction, and hydrogen transfer mode was assumed as the dominated debromination mechanism. The removal process fitted well to the pseudo first-order kinetic equation. The observed rate constants increased with increasing Pd loading and OP-Pd/Fe dosage while decreased with increasing initial BDE15 concentration, the tetrahydrofuran/water ratio, and the initial pH of the solution. The work provides a new approach for the treatment of PBDEs pollution.

Removal of Lead Ions From Aqueous Solutions Using Melamine-Modified Nano Graphene Oxide

Today, due to the industrialization of societies, the existence of heavy metals has created many problems for humans, other organisms, and the environment. Lead (Pb) is highly toxic and the second most commonly used metal. The aim of this study was to evaluate the efficiency of melamine-modified nanographene oxide in the removal of Pb from aqueous media. To increase the efficiency of graphene oxide, it was mechanically converted to nano graphene oxide and melamine (4, 2 and 6-triazine, 3, 1 and 5 triamine). Experiments were performed at pH value of 3-8, temperature of 15-50°C, Pb concentration of 5-200 mg/g, adsorbent dose of 0.01-0.06 g, and contact time of 15- 150 minutes. The mechanism of the adsorption process was investigated using two Langmuir and Freundlich isotherm models, pseudo-first order and pseudo-second order kinetic equations, and thermodynamic equations. The results showed that the adsorption rate corresponds to the Freundlich isotherm model and pseudo-second order kinetic equation. Thermodynamic studies also showed that the adsorption process is associated with increasing irregularities and it is endothermic. In constant conditions (pH of 6, contact time of 60 minutes, ambient temperature of 22°C, Pb concentration of 20 mg/L, and adsorbent dose of 0.01 g), the adsorption capacity was 191.65 mg/g. The highest adsorption occurs at the concentration of 5 mg/L and the highest adsorption capacity and removal percentage was observed at a concentration of 200 mg/L, which were 1896.3 mg/g and 98.8%, respectively. Due to the high adsorption capacity, the adsorbent was able to remove lead from the contaminated environment.

Photocatalysis of Tris-(2-chloroethyl) phosphate by ultraviolet driven peroxymonosulfate oxidation process: Removal performance, energy evaluation and toxicity on bacterial metabolism network

Tris(2-chloroethyl) phosphate (TCEP) as a typical chlorinated-organophosphate esters (OPEs) are identified to be contaminants of emerging concern owing to its health risk and resistance to conventional biological remediation in water matrix. Although ultraviolet-driven radical-based advanced oxidation processes exhibited a well performance in terms of removing refractory emerging organic pollutants, residual biotoxicity and potential environment risks induced by their intermediates products have become a new concern. A comprehensive assessment regarding TCEP elimination using UV-activated peroxymonosulfate (PMS) was performed, which was attempted to provide detailed information about security and fesibility of UV/PMS technology for OPEs control. Degradation of TCEP can be described by a pseudo-first order kinetics equation with a apparent rate constant (0.1311 min−1) and three steady degradation products including C4H9Cl2O4P (m/z 222.969), C2H6ClO4P (m/z 160.976), C6H11Cl2O6P (m/z 280.974) were generated via hydroxylation and dechlorination reactions. The removal efficiency was inhibited in presence of inorganic anions (Cl−, CO32− and H2PO4−), moreover, the inhibitory effects induced by Cl− was more powerful than the other two. Compared to intact TCEP, metabolic pathways were up-regulated expression associated with carbohydrate metabolism, lipid biosynthesis, vitamin metabolism, pyrimidine and purine metabolism, whereas oxidative phosphorylation metabolism, biotin metabolism, oxidation stress response were down-regulated in Escherichia coli exposed to intermediates mixture. The proteomics results confirmed that detoxification of TCEP was achieved in case of an incomplete mineralization, and UV/PMS will be employed as a promising treatment method for controlling micro-pollutants from aquatic environment.

Persulfate-enhanced degradation of ciprofloxacin with SiC/g-C3N4 photocatalyst under visible light irradiation

SiC/g-C3N4 composite (SCN) showed the potential for photocatalytic degradation of synthetic dyes, it is deserved to study whether it is effective for the photocatalytic degradation of ciprofloxacin (CIP). In this work, persulfate-enhanced CIP degradation was investigated with SCN under visible light irradiation. The results showed that the degradation efficiency of 10 mg L−1 CIP could reach 95% for 30 min under the conditions of 0.4 g L−1 SCN, 2 mM persulfate (PS) and solution initial pH 6. The degradation process abided by pseudo first-order kinetic equation, and the observed rate constant (kobs) with SCN/PS (0.132 min−1) was 13 times of that with SCN (0.0102 min−1), and twice of that with g-C3N4/PS (0.0649 min−1). The quenching experiments and electron paramagnetic resonance analysis indicated that O2−· and 1O2 played the main role and other active species (e.g., h+, SO4−· and ·OH) also participated in CIP degradation. The possible degradation pathways were proposed through identifying the intermediate products, and the main reactions may include the ring opening of piperazine, decarbonylation, decarboxylation and defluorination. Bacterial toxicity test showed that the toxicity of the reaction solution decreased dramatically after 30 min degradation. Overall, this work could provide an efficient and environmentally friendly technology for eliminating CIP.