Removal Rate Research Articles

Efficient Degradation of Methyl Violet 10B Dye by Different Light Sources using Boron-doped TiO2-ZnO Photocatalyst

Boron-doped TiO2-ZnO nanocomposite was prepared by sonochemically using boron trichloride, tetra n-butyl orthotitanate and zinc acetate in appropriate proportion. The as-prepared nanocomposite was successfully characterized by XRD, EDX, SEM and BET techniques The operational factors that affect the rate of photocatalytic degradation of methyl violet 10B present in wastewater were optimized, which include initial dye concentration, catalyst amount, pH level and different light intensities such as incandescent light bulb, UV lamp and sunlight. During sonication under sunlight, it was found that the most effective removal rate achieved was 95% when using 0.02 g of B doped TiO2-ZnO per 100 mL of methyl violet 10B solution. The impact of different dye concentrations on the photocatalytic degradation demonstrated the threshold at which concentrations may be readily eliminated. The most effective pollutant degradation was achieved at 5 ppm. The introduction of oxygen using sonophotocatalysis process into the polluted stream enhanced the photocatalytic breakdown of the pollutants. The photocatalyst can be recycled for four cycles without loss the catalyst stability and the degradation rate obeys first-order kinetics.

Optimization of polishing fluid composition for single crystal silicon carbide by ultrasonic assisted chemical-mechanical polishing

Silicon carbide (SiC) is renowned for its exceptional hardness, thermal conductivity, chemical stability, and wear resistance. However, the existing process is difficult to meet the high standards of uniform corrosion in its polishing process and surface roughness and flatness after polishing, new polishing fluids and technique optimization are crucial for development. The study optimized and validated the composition of the polishing fluid used in ultrasonic-assisted chemical-mechanical polishing (UACMP). Abrasives significantly influenced the material removal rate (MRR) and surface roughness (Ra), contributing 67.63% and 56.43%, respectively. Organic bases and pH buffers significantly affected Ra, accounting for 19.66% and 21.44%, respectively. The optimum composition was determined, consisting of triethylamine (3wt%), potassium hydrogen phthalate (1wt%), a composite of silica and alumina abrasive particles (5wt%), and hydrogen peroxide (6wt%), which reduced the Ra from 95 nm to 3 nm. The MRR achieved 25.96 nm/min. In comparison to the 7 nm minimum roughness from the orthogonal test, the optimal scheme’s Ra was reduced by 57.14%, leading to a significant enhancement in overall surface quality. In this paper, a new type of additive is added to prepare the polishing liquid, which provides a new idea for the UACMP of SiC and has a great impact.

Fundamental study on dielectric oil viscosity for high-performance wire EDM

AbstractDielectric oil has been recently used in wire electrical discharge machining (wire EDM) for achieving high-precision machining. However, the influence of dielectric oil properties on wire EDM characteristics has not been clarified sufficiently. This study fundamentally investigated the influence of dielectric oil viscosity on wire EDM characteristics. In this study, three types of dielectric oil differing only in viscosity were prepared and examined. Linear cutting experiment results showed that the removal rate and the machined surface roughness increase with dielectric oil viscosity. Then, the influence of viscosity on crater removal volume was investigated to discuss the cause of the change in removal rate, and it was found that crater removal volume increases with the viscosity. Furthermore, CFD (computational fluid dynamics) analysis results and discharge observation results showed that the debris exclusion becomes worse in higher viscosity oil, and the discharge concentration occurs frequently, resulting in the deterioration in machined surface roughness. Next, the difference in machining accuracy with dielectric oil viscosity was investigated. It was found that the corner shape accuracy deteriorates with the increase of viscosity while the machined surface waviness and straightness improve slightly. Structural analysis results showed that wire deflection increases with viscosity, resulting in the deterioration in corner shape accuracy. On the other hand, high-speed observation of wire vibration was carried out, and it was found that the wire vibration decreases in the case of higher viscosity, which leads to the improvement in machined surface waviness and straightness.

Magnetic coal gangue-based catalysts for peroxymonosulfate activation and benzo[a]pyrene degradation: The construction of Fe and N dual active sites

The magnetic coal gangue (CG)-based catalysts were successfully prepared by impregnation-calcination method with iron (Fe) and nitrogen (N) co-doping for peroxymonosulfate (PMS) activation, illustrating excellent catalytic property with 100.00 % removal rate of benzo[a]pyrene (BaP). Additionally, Fe/N co-doped CG catalysts (Fe-N-CG) possess desirable performance against co-existing anions and organic matter (HA), with a nearly 80.00 % removal rate in actual water systems. The mechanism of activating PMS and removing BaP was comprehensively analyzed through a series of characterizations and experiments, proving that the Fe and N double reaction sites could enhance the contribution of radical paths and non-radical paths for BaP degradation. Finally, the safety and prospects for practical environmental remediation via Fe-N-CG for PMS activation were further evaluated by ECOSAR toxicity analysis software and mung bean growth experiments. In summary, the development of Fe-N-CG widened the high-value utilization of CG and supplied a deep insight into the restoration of organically polluted environments.

Preparation of Loess‐Clay Based Eco‐Friendly Geopolymer for Efficient Removal of Pollutants in Water

AbstractHeavy metals and dyes cause serious harm for water environment, geopolymer materials with the large pores and specific surface area, and easy modification of pore surface have received extensive attention in wastewater treatment. Herein, using loess‐clay (LC) as natural mineral materials, we developed an eco‐friendly geopolymer of loess‐clay (GpLC) with excellent adsorption properties and promotion plant growth was prepared by alkali excitement. Its morphology and structure were exhibited by scanning electron microscopy, Fourier transform infrared spectroscopy, XRD, and Brunauer–Emmett–Teller. Moreover, its adsorption property for removing metal ions and different dyes was measured, and the adsorption kinetics and thermodynamics were investigated. GpLC presented excellent adsorption ability for Pb2+, which the removal rate got to 98.7 %. It had the universality of removing organic pollutants, and the removal rate reached to 98.0 %. It was dominated chemisorption and single‐layer adsorption, which GpLC conformed to quasi‐second‐order adsorption kinetics, and being more consistent with Langmuir isothermal model. Furthermore, it was found that GpLC could promote growth of crops as it contain P and K element with essential element of plants. In summary, it provides insights and strategy for developing a kind of eco‐friendly functional materials with strong adsorption capacity and promoting plant growth, and it is an effective method for reusing loess resources.

Multi‐objective optimization of ultrasonic vibration‐assisted drilling in carbon fiber reinforced polyetherketoneketone laminate

AbstractCarbon fiber reinforced polyetherketoneketone (CF/PEKK) possess excellent mechanical properties and also meet low‐carbon environmental standards, leading to their increasingly widespread application in recent years. To ensure the strength of mechanical connections, it is crucial to minimize drilling damage. This paper utilizes Ultrasonic Vibration‐Assisted Drilling (UVAD) to enhance hole‐making quality, comparing multiple drilling performance indicators with Conventional Drilling (CD), including thrust force, drilling temperature, delamination factor, and burr factor. The results demonstrate that UVAD significantly reduces thrust force and drilling temperature, decreases delamination and burring damage, and effectively improves hole quality. To further optimize processing parameters, the Non‐dominated Sorting Genetic Algorithm II (NSGA‐II) was used, targeting thrust force, Material removal rate (MRR), and delamination factor as optimization goals. The reliability of the model was verified through experimentations. This paper provides an effective technical approach for high‐quality drilling in CF/PEKK materials, offering significant practical application value for material processing in aerospace and other fields.Highlights The quality of CF/PEKK processed by CD and UVAD was compared. UVAD can effectively improve the quality of drilling. The drilling parameters were optimized by NSGA‐II. The reliability of the prediction model was verified by experiments.

Peroxymonosulfate Activation by Rice-Husk-Derived Biochar (RBC) for the Degradation of Sulfamethoxazole: The Key Role of Hydroxyl Groups

In this work, rice-husk-derived biochar (RBC) was synthesized by using simple one-step pyrolysis strategies and served as catalysts to activate peroxymonosulfate (PMS) for degrading sulfamethoxazole (SMX). When the annealing temperature (T) = 800 °C, RBC800 exhibits the typical hardwood structure with several micropores and mesoporous. Furthermore, RBC800 obtains more defect sites than RBC600, RBC700, and RBC900. In the RBC800/PMS system, the removal rate of the SMX reached 92.0% under optimal conditions. The kinetic reaction rate constant (kobs) of the RBC800/PMS system was 0.009 min−1, which was about 1.50, 1.28, and 4.50 times that of the RBC600/PMS (kobs = 0.006 min−1), RBC700/PMS (kobs = 0.007 min−1), and RBC900/PMS (kobs = 0.002 min−1) systems, respectively. In the RBC800/PMS system, sulfate radical (SO4•−) is the main active species. Compared with other active sites, the hydroxyl group (C-OH) on the surface of RBC800 interacts more strongly with PMS, which is more likely to promote the stretching of the O-O bond of the PMS, thus breaking into the activated state and significantly reducing the activation energy required for reaction. The degradation intermediates of SMX were speculated, and the toxicity analysis was conducted. Generally, this work reveals in depth the interaction between reactive sites of biochar-based catalysts and PMS at the molecular level.

Effects of oxidizer concentration and abrasive type on interfacial bonding and material removal in 4H-SiC polishing processes.

Determination of chemical effects involved in material removal during the polishing process of 4H-SiC has been a challenge. In this study, the polishing processes of 4H-SiC under the action of diamond and SiO2 abrasive in different concentrations of H2O2 solutions are investigated by reactive force field molecular dynamics simulations. It is found that 4H-SiC can be oxidized by H2O2 solution at the atomic scale, but the chemical reaction alone does not lead to material removal. An increase in the concentration of H2O2 solution and the mechanical action of abrasives can promote the oxidation of 4H-SiC. Since the mechanical removal dominates material removal when polishing 4H-SiC with diamond abrasive, there is no clear pattern in the effect of H2O2 solution concentration on material removal. Nevertheless, the removal of atoms associated with chemical bonds dominates material removal when polishing 4H-SiC with SiO2 abrasive. Therefore, the damage and atomic removal of 4H-SiC are lower. Since the H2O2 solution can increase the total number of bonds between 4H-SiC and SiO2 abrasive, an increase in the concentration of H2O2 solution can improve the material removal rate. These findings can provide guidance for the 4H-SiC polishing process in terms of abrasive and oxidizer selection.

Multiobjective optimization of magnetic abrasive finishing process with periodic re-distribution of magnetic abrasive particles on 17-4PH stainless steel

Magnetic abrasive finishing (MAF) exhibits considerable potential as a promising process for enhancing surface finish quality for softer as well as harder materials. This work proposes a novel approach to harness the potential of MAF for obtaining superior surface quality of precipitation-hardening martensitic steel (17-4PH steel) while performing periodic re-distribution of magnetic abrasive particles. The experiments were conducted using the Box-Behnken design of experiments and response surface methodology (RSM). RSM-based desirability function approach and genetic algorithms were used for multiobjective optimization. The set of pareto-optimal solutions obtained through multiobjective optimization were ranked using the Technique for Order of Preference by Similarity to an Ideal Solution (TOPSIS) by assigning equal importance to the selected performance parameters (percentage change in surface roughness (PCSR) and material removal rate (MRR)). The optimized values of PCSR and MRR obtained through the desirability function of RSM and genetic algorithm were validated experimentally and compared with the predicted values obtained through the regression model. Results showed that the desirability function of RSM provided better results than the genetic algorithm for the selected conditions and confirmed the effectiveness of the proposed approach.

Validated kinetic modelling of ladle furnace process for predicting inclusions in API steel grade

A kinetic model of ladle furnace (LF) process is developed in C++ format using the FactSage database and ChemApp subroutines. The model considers all the process parameters such as ferroalloy and slag dissolution, wire additions, electrical arcing, steel/slag reactions, reoxidation due to slag eye opening, heat exchange between metal/slag, and refractory dissolution. Further, a correlation for inclusion removal rate was developed as a function of argon flow rate, using discrete phase method (DPM) in Computational Fluid dynamics (CFD). Lollypop samples from steel bath and slag samples were collected from the plant for API steel grade for chemical analysis and inclusion characterisation. At LF_in, the inclusions found were mostly alumina spinel with very low amount of Mg (∼3%), followed by spinel at intermediate stage having ∼15 wt. % of Mg and after Ca treatment, inclusions transformed into CaS and Calcium Aluminate type of inclusions. Overall inclusion weight fraction varied from 136 ppm at LF_in to 93 ppm at LF_out. The model calculations were found to give very good prediction for steel and slag chemistry, and inclusion global composition as compared to the plant results. Predicted temperature was found with an accuracy of ± 5 oC, while the calculated inclusion weight fraction was having an accuracy of ±12 ppm.

Mutations of methionine 444 interacting with T1Cu-coordinating amino acids affect the structure and function of multicopper oxidase CopA.

Manganese is an essential trace element for humans, animals, and plants, but excessive amounts of manganese can cause serious harm to organisms. The biological manganese oxidation process mainly oxidizes Mn(II) through the secretion of unique manganese oxidase by manganese-oxidizing bacteria. The T1 Cu site of multicopper oxidase is the main site for substrate oxidation, and its role is to transfer electrons to TNC, where dioxygen reduction occurs. In this study, methionine (Met) No. 444 interacting with the T1Cu-coordinating amino acid in the multicopper oxidase CopA from Brevibacillus panacihumi MK-8 was mutated to phenylalanine (Phe) and leucine (Leu) by the enzyme. Based on the analysis of enzymatic properties and the structural model, the mutant protein M444F with 4.58 times the catalytic efficiency of the original protein CopA and the mutant protein M444L with 1.67 times the catalytic efficiency of the original protein CopA were obtained. The study showed that the manganese removal rate of the manganese-oxidizing engineered bacterium Rosetta-pET-copAM444L cultured for 7 days was 88.87%, which was 10.77% higher than that of the original engineered bacterium. Overall, this study provides a possibility for the application of genetic engineering in the field of biological manganese removal.

Activation of peroxomonosulfate by manganese-containing non-homogeneous catalysts prepared via a soft template calcination strategy for efficient degradation of carbamazepine

Manganese (Mn)-containing inhomogeneous catalysts have demonstrated potential to activate peroxymonosulfate (PMS), but may be constrained by low efficiency and poor resistance to environmental disturbances. According to the soft template calcination strategy, g-C3N4 with Mn doping was synthesized to improve PMS activation through an effective Mn(II)/Mn(III)/Mn(IV) cycle. The constructed Mn25@CN/PMS system achieved complete and rapid removal of carbamazepine (CBZ) at 0.3 g/L catalyst and 2 mM PMS. Its corresponding rate constant of pseudo-first-order was 0.3424 min−1, and it was 3424 and 16.15 times higher than that of pure g-C3N4/PMS system and CN/PMS system, respectively. More strikingly, the catalysts exhibited excellent resistance to environmental impacts, with CBZ removal rates exceeding 95% under the influence of different anions, cations, aqueous pH values, and humic acid (HA) concentrations. Subsequently, it was proposed a reliable catalytic mechanism for CBZ removal and PMS activation derived from electron paramagnetic resonance (EPR) tests and quenching experiments. The O2·- and 1O2 played a major role in the CBZ removal process. This research provides a perspective soft template strategy for PMS activation using highly efficient catalysts with high resistance to environmental impacts, which provides new ideas to alleviate environmental issues.

Upcycling of steel slag to activate persulfate for the degradation of chlortetracycline hydrochloride: Performance and mechanism

ABSTRACT Steel slag has great potential as an Fe-based heterogeneous Fenton-like catalyst because of its high iron content and low cost. However, the iron compounds are often encapsulated by calcium or silicon compounds in the steel slag. Herein, steel slag powder was acid-modified with salicylic acid to remove some Ca–Si compounds and thus expose more iron active sites. The results showed that the calcium content significantly decreased from 36.33 to 20.54% after modification, and more transition metals of Fe and Mn with catalytic activities were exposed simultaneously. During the activation of peroxysulphate, the conversion of Fe(Ⅱ) to Fe(Ⅲ) occurs and large amounts of •OH and 1O2 are produced as the main reactive oxygen species. The removal rates of CTC and TOC are 93.42 and 46.05%, respectively, and a degradation process may also be inhibited by CO32−, H2PO4−, and humic acid (HA). The degradation pathways of CTC mainly include both dechlorination and demethylation. In addition, salicylic acid-modified steel slag shows good repeated usability, and its removal ability is maintained at higher than 80% after four times of recycling. This study provides a new idea for designing an efficient and cheap catalyst to treat organic wastewater.

Ornamental Plant Growth in Different Culture Conditions and Fluoride and Chloride Removals with Constructed Wetlands

Natural water resources often contain fluorides and chlorides due to wastewater discharge; however, excessive exposure to fluorides can pose health risks to humans. Elevated chloride levels can negatively affect aquatic fauna and disrupt the reproductive rates of plants. This study assessed constructed wetlands (CWs) featuring monocultures (including Canna hybrid, Alpinia purpurata, and Hedychium coronarium) and polycultures (combinations of species from the monoculture systems) of ornamental plants (OPs) to evaluate their efficiency in removing fluorides and chlorides. The results revealed that the ornamental plants flourished in the CW conditions without sustaining any physical damage. C. hybrid demonstrated the longest roots and the highest volume, as well as greater height compared to other species. However, this did not affect the ion removal efficiency. In polyculture systems, 42.2 ± 8.8% of fluoride was removed, a result that was not significantly different (p > 0.05) from the removal rates observed in monocultures of C. hybrid (42.5 ± 7.5%), H. coronarium (36.8 ± 7.0%), or A. purpurata (30.7 ± 7.9%). For chloride, a similar pattern emerged, with 32.4 ± 4.8% removed in constructed wetlands (CWs) using a polyculture of ornamental plants, a figure that was also not significantly different (p > 0.05) from the removal percentages in monocultures of C. hybrid (29.1 ± 5.3%), H. coronarium (28.1 ± 5.0%), or A. purpurata (32.0 ± 5.7%). Our results indicate that CWs with polyculture species contribute to pollutant removal at levels comparable to those found in monoculture systems. However, polyculture systems offer enhanced aesthetic appeal and biodiversity, incorporating various ornamental flowering plants. The use of this eco-technology for removing fluoride and chloride pollutants helps prevent river contamination and associated health issues.

Bioremediation of metal cyanide complexes from electroplating wastewater for long-term application using Agrobacterium tumefaciens SUTS 1 and Pseudomonas monteilii SUTS 2.

The purpose of this study was to investigate the optimum conditions, including aerobic and anoxic conditions, for operating a long-term bioreactor system to decrease the toxicity of industrial electroplating wastewater effluents containing metal cyanide using Agrobacterium tumefaciens SUTS 1 and Pseudomonas monteilii SUTS 2. The initial results revealed that bacteria performed better under aerobic conditions than under anoxic conditions. An aerobic bioreactor system was subsequently set up in a long-term study lasting 30days under optimum operating conditions. Both mixed-culture bacteria and indigenous bacteria promoted the high-efficiency treatment of cyanide and metals in the first 7days of the study. When the system had high removal rates, cyanide removal was greater than that of zinc, copper, nickel, and chromium (CN- > Zn > Cu > Ni > Cr), with removal efficiencies of 96.67%, 93.93%, 74.17%, 63.43%, and 44.65%, respectively, with residual concentrations of 0.15 ± 0.01, 0.24 ± 0.005, 0.03 ± 0.002, 18.41 ± 0.06 and 14.26 ± 0.15mg/L, respectively. The cell concentration in the bioreactor increased to approximately 107CFU/mL over 30days from initial cell concentrations of 6.15 × 105 CFU/mL and 1.05 × 103CFU/mL for the mixed culture and indigenous inoculation, respectively. These results implied that the bacteria were resistant to heavy metal toxicity. The addition of an appropriate carbon source with sufficient aeration to a bioreactor resulted in increased cyanide degradation.

Combined effect of flocculation and ammonia stripping on different biogas slurries

The combined use of flocculation and ammonia stripping could be an efficient method for treating biogas slurry (BS). In this study, the operating parameters of ammonia stripping after flocculation were optimized. Swine manure biogas slurry (SMBS) and chicken manure biogas slurry (CMBS) were used as raw materials, and the flocculation efficiency and ammonia nitrogen removal rate (ANRR) were the main indices to evaluate the process performance. The bioflocculant (BF), polyaluminium chloride (PAC), ferric chloride (FC), and calcium oxide (CaO) were used as flocculants for the different biogas slurry flocculation. The results showed that CaO was more suitable for SMBS; the flocculation efficiency reached 56.63 % at the additive concentration of 5 g/L. Moreover, the ANRR was significantly improved by over 80 % after flocculation. However, the best flocculation potential on CMBS was achieved at an additive concentration of 0.3 g/L, and the flocculation efficiency reached 44.44 %. The ANRR reached 94.42 % at 45 ℃. This study provides a scientific basis and feasible scheme for treating different BS.

Experimental Study on the Removal of Pollutants from Domestic Wastewater in a Strongly Constructed Wetland with an Applied Electric Magnetic Field

The addition of physical field enhancement measures to improve the purification effect of vertical flow artificial wetlands has gradually become popular. In this study, a vertical flow artificial wetland system reinforced by electric and magnetic fields was constructed. These fields were first optimized using finite element 3D simulation software to obtain the optimal electric and magnetic field parameters. Then, the pollutant removal effects and changes in microbial community structure were comparatively analyzed. The optimal electromagnetic field parameters (applied voltage of 15 V and applied magnetic field of 20 mT) resulted in significantly enhanced removal rates of chemical oxygen demand (COD), nitrate nitrogen (NH4+-N), total phosphorus (TP), and orthophosphorus (PO43−-P) in wastewater, with rates of 74.47%, 45.44%, 89.85%, and 90.04%, respectively. These rates were notably higher than those observed in the vertical flow artificial wetland system. The microbial community structure analysis revealed that the vertical flow constructed wetland with enhanced electric and magnetic fields exhibited (EM-VFCW) a more diverse and complex microbial community structure. Notably, the abundance of bacteria capable of removing NH4+-N and COD, including Aspergillus, Fusarium, and Actinobacteria, was significantly elevated.

Optimizing dry milling of stir-cast and heat-treated AZ80 magnesium alloy using multiple criteria optimization technique: an experimental study.

The primary aspects of this research are to evaluate surface roughness, cutting force, and material removal rate and optimize it with dry milling process parameters for heat-treated and stir-cast AZ80 magnesium alloy. Multiple methodologies are utilized in the research, which includes the Integration of design of experiments-response surface methodology for experimental design with the technique for order of preference by similarity to ideal solution for multi-criteria optimization. In order to evaluate the effect of process parameters on the response, the experimental design manipulates the depth of cut, feed rate, and cutting speed in a systematic manner. An evaluation of the machined surface's quality is conducted via surface roughness measurements. Likewise, insights into the forces exerted during milling can be obtained through continuous monitoring of cutting forces. The calculation of material removal rate is predicated on weight reduction. The interaction between the depth of cut and feed rate has a significant impact on the critical-to-quality characteristics of the alloy, which has contribution percentage greater than 25%. This finding validates that despite the heat-treated alloy having a similar composition to the as-cast alloy (where the closeness coefficient is 0.9843), the optimal process parameters of the former are not applicable to the latter. Nevertheless, the technique used to prepare the specimen has no bearing on the material removal rate, which is a process parameter-specific effect.

Investigation of EDM erosion behavior for Ni-based superalloy using experimental and machine learning approach

The rapid growth of the global population and the consequent increase in manufacturing activities have heightened the need for sustainable practices to protect the environment. Non-traditional manufacturing processes, such as electric discharge machining (EDM), often use oil-based dielectric fluids like kerosene, which emit toxic fumes and aerosols, contributing to environmental pollution. To address this, the reuse of waste cooking oil (WCO) as a dielectric fluid in EDM presents a promising solution. This method not only tackles the issue of waste oil disposal but also supports the circular economy by repurposing waste materials. EDM, frequently criticized for its low cutting rates, can be enhanced by using nitrogen assisted modified Cu electrodes (cryogenically treated (CT)). This study focused on machining the difficult-to-cut nickel-based superalloy, IN718 by incorporating Sillimanite nano-powder with Span-60 (S-60). The erosion performance characteristics such as material removal rate (MRR), electrode wear rate (EWR), and accuracy index (AI) were evaluated. An artificial neural network (ANN) was employed to predict and correlate experimental and predicted values. Significant improvements were achieved using the non-dominated sorting genetic algorithm (NSGA-II) in the confirmation investigations. With a non-treated (NT) Cu electrode, the confirmatory experiments showed a 79.81 % increase in MRR, an 18.99 % decrease in EWR, and a 0.89 % improvement in AI. For the CT Cu electrode, MRR increased by 85.48 %, EWR decreased by 32.90 %, and AI improved by 0.53 % when using optimal processing parameters. This study demonstrates the potential for significant environmental and performance benefits in EDM by reusing WCO and optimizing electrode treatments.

Remediation of hexavalent chromium in water and soil by pristine and chemically modified pine barks: Effects and mechanisms

Chemical modification can greatly improve the adsorption performance of materials. In this study, pristine pine bark (PB) was modified by phosphoric acid (PA-PB), dodecyl trimethylammonium bromide (DTAB-PB) and cetyl trimethylammonium bromide (CTAB-PB) to test their influence on remediating hexavalent chromium [Cr(Ⅵ)] contamination in water and soil systems. Under the optimal experimental conditions in solution, the reduction/adsorption capacities and removal rates of Cr(Ⅵ) follow the order of CTAB-PB > PA-PB > DTAB-PB > PB, with CTAB-PB showing the highest capacity of 88.1 mg g−1. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) indicated that adsorption coupled with reduction were the responsible mechanisms for Cr(Ⅵ) removal by pristine and modified PB, and modification with CTAB greatly improved Cr(Ⅵ) removal, especially the reduction of Cr(Ⅵ). When CTAB-PB and PB were applied in soil for a 30-day microcosm experiment, more than 93 % of Cr(Ⅵ) was converted into Cr(Ⅲ) at four different addition levels (2, 5, 10, and 15 wt%) with CTAB-PB exhibiting a faster immobilization rate than PB. In conclusion, CTAB-PB showed better performance than PB and is a promising material for the remediation of Cr(Ⅵ) contamination in water and soil.