Removal Process Research Articles

Nano-Perforated Silicon Membrane with Monolithically Integrated Buried Cavity

A wafer-scale process for fabricating monolithically suspended nano-perforated membranes (NPMs) with integrated support structures into silicon is developed. Existing fabrication methods are suitable for many desired geometries, but face challenges related to mechanical robustness and fabrication complexity. We demonstrate a process that utilizes the cyclic deposit, remove, etch, and multi-step (DREM) process for directional etching of high-aspect-ratio (HAR) 300 nm in diameter nano-pores of 700 nm pitch. Subsequently, a buried cavity beneath the nano-pores is formed by switching to an isotropic etch, which effectively yields a thick NPM. Due to this architecture’s flexibility and process robustness, structural parameters such as membrane thickness, diameter, integrated support structures, and cavity height can be adjusted, allowing a wide range of NPM geometries. This work presents NPMs with final thicknesses of 4.5 µm, 6.5 µm, and 12 µm. Detailed steps of this new approach are discussed, including the etching of a through-silicon-via to establish the connection of the NPM to the macro-world. Our approach to fabricating NPMs within single-crystal silicon overcomes some of the limitations of previous methods. Owing to its monolithic design, this NPM architecture permits further enhancements through material deposition, pore size reduction, and surface functionalization, broadening its application potential for corrosive environments, purification and separation processes, and numerous other advanced applications.

Parametric optimization of abrasive waterjet machining for aluminum 7075/boron carbide/zirconium silicate hybrid composites

In the present work, an attempt was made to study the machining characteristics of Hybrid Metal Matrix Composites (HMMCs) using Abrasive Waterjet Machining (AWJM). For preparing the composites, Aluminum alloy 7075 is cast with boron carbide (B4C) and zirconium silicate (ZrSiO4) reinforcement by the method of stir casting. Experimental investigation of the machining parameters on Depth of Cut (DoC), Material Removal Rate (MRR), and Surface Roughness (SR) was done. The independent parameters include Abrasive Mesh Size (AMS), Abrasive Flow Rate (AFR), Water Jet Pressure (WJP), and Traverse Rate (TR). The results of experiments reveal that low TRs increase SR, while short AMSs, high flow rates, and large WJPs increase DoC and MRR. Surface maps made by SEM exposed information about the surface texturing and the material removal processes. It was found that the optimal DoC was achieved at an AMS 80#, AMS of 340 g/min, WJP of 200 MPa, and TR of 60 mm/min for both unreinforced Al and the composite of Al + 5% B4C + 5% ZrSiO4. The results enable the development of proper AWJM procedures for HMMCs to ensure better surface finish and workability. From the experiments, it was observed that while smaller mesh sizes and greater AFR will improve MRR and DoC, it can at the same time have a negative effect on the overall performance of Kerf Taper angle (KT) and Surface Roughness (SR).

Single-cell phenotyping of extracellular electron transfer via microdroplet encapsulation.

Electroactive organisms contribute to metal cycling, pollutant removal, and other redox-driven environmental processes via extracellular electron transfer (EET). Unfortunately, developing genotype-phenotype relationships for electroactive organisms is challenging because EET is necessarily removed from the cell of origin. Microdroplet emulsions, which encapsulate individual cells in aqueous droplets, have been used to study a variety of extracellular phenotypes but have not been applied to investigate EET. Here, we describe the development of a microdroplet emulsion system to sort and enrich EET-capable organisms from complex populations. We validated our system using the model electrogen Shewanella oneidensis and described the tooling of a benchtop microfluidic system for oxygen-limited conditions. We demonstrated the enrichment of strains exhibiting electroactive phenotypes from mixed wild-type and EET-deficient populations. As a proof-of-concept application, we collected samples from iron sedimentation in Town Lake (Austin, TX) and subjected them to microdroplet enrichment. We measured an increase in electroactive organisms in the sorted population that was distinct compared to a population growing in bulk culture with Fe(III) as the sole electron acceptor. Finally, two bacterial species not previously shown to be EET-capable, Cronobacter sakazakii and Vagococcus fessus, were further cultured and characterized for electroactivity. Our results demonstrate the utility of microdroplet emulsions for isolating and identifying EET-capable bacteria.IMPORTANCEThis work outlines a new high-throughput method for identifying electroactive bacteria from mixed populations. Electroactive bacteria play key roles in iron trafficking, soil remediation, and pollutant degradation. Many existing methods for identifying electroactive bacteria are coupled to microbial growth and fitness-as a result, the contributions from weak or poor-growing electrogens are often muted. However, extracellular electron transfer (EET) has historically been difficult to study in high-throughput in a mixed population since extracellular reduction is challenging to trace back to the parent cell and there are no suitable fluorescent readouts for EET. Our method circumvents these challenges by utilizing an aqueous microdroplet emulsion wherein a single cell is statistically isolated in a pico- to nano-liter-sized droplet. Then, via fluorescence obtained from copper reduction, the mixed population can be fluorescently sorted and gated by performance. Utilizing our technique, we characterize two previously unrecognized weak electrogens Vagococcus fessus and Cronobacter sakazakii.

A Pore-Scale Investigation of Oil Contaminant Remediation in Soil: A Comparative Study of Surfactant- and Polymer-Enhanced Flushing Agents

Pore-scale remediation investigation of oil-contaminated soil is important in several environmental and industrial applications, such as quick responses to sudden accidents. This work aims to investigate the oil pollutant removal process and optimize the oil-contaminated soil remediation performance at the pore scale to find the underlying mechanisms for oil removal from soil. The conservative forms of the phase-field model and the non-Newtonian power-law fluid model are employed to track the moving interface between two immiscible phases, and oil pollutant flushing removal process from soil pores is investigated. The effects of viscosity, interfacial tension, wettability, and flushing velocity on pore-scale oil pollutant removal regularity are explored. Then, the oil pollutant removal effects of two flushing agents (surfactant system and surfactant–polymer system) are compared using an oil content prediction curve based on UV-Visible transmittance. The results show that the optimal removal efficiency is obtained for a weak water-wetting system with a contact angle of 60° due to the stronger two-phase fluid interaction, deeper penetration, and more effective entrainment flow. On the basis of the dimensionless analysis, a relatively larger flushing velocity, resulting in a higher capillary number (Ca) in a certain range, can achieve rapid and efficient oil removal. In addition, an appropriately low interfacial tension, rather than ultra-low interfacial intension, contributes to strengthening the oil removal behavior. A reasonably high viscosity ratio (M) with a weak water-wetting state plays synergetic roles in the process of oil removal from the contaminated soil. In addition, the flushing agent combined with a surfactant and polymer can remarkably enhance the oil removal efficiency compared to the sole use of the surfactant, achieving a 2.5-fold increase in oil removal efficiency. This work provides new insights into the often-overlooked roles of the pore scale in fluid dynamics behind the remediation of oil-contaminated soil via flushing agent injection, which is of fundamental importance to the development of effective response strategies for soil contamination.

Composite Treatment Module for Removing Acidity and Metal (Loid)S from Acid Rock Drainage

This study evaluates a two-stage approach for remediating acid rock drainage (AMD) generated from an abandoned coal mine site. The method combines the adsorption and chemical precipitation properties of drinking water treatment residue (WTR) in a continuous flow-through fluidized filter bed with hydroponic phytoremediation using Vetiver grass to remove dissolved metal(loid)s. In the first stage, the filter demonstrated exceptionally high removal efficiencies for several metals, including up to 99.67% of Al (<1 mg/L), 99.46% of Fe (<2 mg/L), and 92.48% of As. Significant removal efficiencies were also achieved for Zn (69.24%) and Cu (62.85%). However, relatively low removal efficiencies were observed for Mn (12.50%), Ni (26.74%), and Co (21.36%). Additionally, the system effectively reduced acidity, increasing the pH from 2.67 to a near-neutral level of 6.13. The second stage, a 30-day Vetiver grass treatment, further reduced Mn concentrations by 56.9%, improving upon the limited Mn removal observed in the fluidized filter column. This underscores the complementary role of hydroponic phytoremediation in enhancing the overall metal removal process. This innovative and cost-effective system demonstrates significant potential for AMD remediation, achieving simultaneous removal of metal(loid)s and neutralizing acidity in contaminated mine water.

Design and Realization of a Cutting Force Measuring System to Analyze the Chip Removal Process in Rotational Turning

This study focuses on a detailed analysis of the cutting forces in rotational turning, a novel machining process designed to achieve high surface quality and productivity. Unlike traditional longitudinal turning, rotational turning employs a helical cutting-edged tool that performs a circular feeding movement, introducing complex kinematics that complicates the accurate measurement of the cutting forces. To address this, the theoretical background was described for modeling the cutting force removal. The process was experimentally simulated on a CNC milling machine using a custom-designed measurement system. The major cutting force, passive force, and feed force were successfully measured and analyzed under varying feed conditions for both rotational and longitudinal turning. The results demonstrate a significant reduction in the passive force during rotational turning compared to longitudinal turning, which directly contributes to lower elastic deformation in the radial direction of the workpiece. This reduction improves the dimensional accuracy and stability during machining. Additionally, the feed force was observed to be slightly higher in rotational turning, reflecting the influence of the rotational movement of the tool. These findings highlight the advantages of rotational turning for applications requiring precision and surface quality, particularly where radial deformation is a critical concern. This study establishes a reliable methodology for force measurement in rotational turning and provides valuable comparative insights into its performance relative to conventional turning processes.

Degradation of X-Ray Contrast Media in Anaerobic Membrane Bioreactors

The presence of pharmaceutical compounds, including iodinated contrast media (ICM), in aquatic systems poses significant ecological and health risks due to their biological activity at low concentrations. This study investigated the removal efficiency of three selected ICM—diatrizoate, iohexol, and iodipamide—from synthetic hospital wastewater using anaerobic membrane bioreactors (MBRs) operated at varying sludge ages of 40, 70, and 100 days. The results indicated that the performance of the MBRs in removing organic compounds improved with increased sludge age. Diatrizoate exhibited the highest removal efficiency, achieving 72% at a sludge age of 40 days and nearly 90% at 70 and 100 days, with no substantial differences between the two higher sludge ages. In contrast, iohexol and iodipamide demonstrated relatively low and inconsistent removal efficiencies, reaching a maximum of 40%, with no observable dependency on sludge age. The findings underscore the importance of optimizing sludge age in biological treatment processes for effective ICM removal.

Loading of anionic surfactant on eco-friendly biochar and its applications in Cr(VI) removal: adsorption, kinetics, and reusability studies

Surfactant-modified biochar is a viable adsorbent for eliminating Cr(VI) from synthetic wastewater. The biochar obtained from the zea mays plant (BC) was tailored with sodium dodecyl sulfate (SDS) as an anionic surfactant forming SDS-BC adsorbent. Different controlling conditions have been evaluated including pH of the solution, biomass concentration, primary Cr(VI) concentration, time of adsorption, and temperature. Under the best controlling circumstances, the percentage of removal has attained 99%. The pseudo-second-order kinetic model best described the removal process, according to the kinetic data, while the Temkin model, one of the applicable adsorption isotherm models, well expressed the adsorption process. The thermodynamic parameters were computed, which disclosed the spontaneity and exothermic character of the Cr(VI) elimination. According to the regeneration cycles, SDS-BC was cost-effective and had a good removal capability.Graphical

Transformation fate of bisphenol A in aerobic denitrifying cultures and its coercive mechanism on the nitrogen transformation pathway.

Bisphenol A (BPA) is a commonly used endocrine-disrupting chemical found in high levels in wastewater worldwide. Aerobic denitrification is a promising alternative to conventional nitrogen removal processes. However, the effects of BPA on this novel nitrogen removal process have rarely been reported. Herein, we investigated the removal and interaction effects of BPA (0, 0.1, 1, and 10 mg/L) in aerobic denitrifying cultures. Our experimental results demonstrated that the aerobic denitrification system could remove 66%-86% of BPA from wastewater. Fourier transform infrared spectroscopy revealed that polysaccharides and amides were the primary sites for adsorption. An increase in the type and number of intermolecular hydrogen bonds might enhance the ability of aerobic denitrifying cultures to adsorb BPA. Adsorption kinetics analysis demonstrated that inhomogeneous multilayer adsorption was the leading cause of BPA removal. Adsorbed BPA decreased the sedimentation, flocculation, and hydrophobicity of aerobic denitrifying cultures, triggering changes in the levels of proteins and polysaccharides in extracellular polymeric substances. As the influent BPA increased from 0 to 10 mg/L, the nitrate-nitrogen and total organic carbon in the reactor effluent increased from 0.4 ± 0.2 and 26 ± 7.9 mg/L to 18.8 ± 9.3 and 116.2 ± 55.6 mg/L, respectively. BPA (initial concentration range: 1-10 mg/L) significantly influenced the abundance of genes involved in the nitrogen transformation pathway, contributing to the increase in the abundance of gaseous NOx-transformed genes and altering the relative abundance of denitrifying bacteria, particularly Thauera. Correlation analyses revealed that Pseudomonas, Thauera, and AKYH767 are important for maintaining systemic nitrogen transformations and BPA adsorption.

Removal of Ampicillin with Nitrifying Cultures in a SBR Reactor.

The presence of antibiotics in wastewater discharges significantly affects the environment, mainly due to the generation of bacterial populations with multiple antibiotic resistances. The cometabolic capacity of nitrifying sludge to simultaneously remove ammonium (NH4+) and emerging organic contaminants (EOCs), including antibiotics, has been reported. In the present study, the removal capacity of 50mg ampicillin (AMP)/L by nitrifying cultures associated with biosorption and biotransformation processes was evaluated in a sequencing batch reactor (SBR) system. The contribution of nitrifying enzymes (ammonium monooxygenase (AMO) and nitrite oxidoreductase (NOR)) and β-lactamases in AMP biodegradation was evaluated using specific inhibitors in batch cultures. AMP was 100% eliminated after 5h since the first cycle of operation. The sludge maintained its ammonium oxidizing capacity with the total consumption of 102.0 ± 2.5mg NH4+-N/L in 9h, however, the addition of AMP altered the nitrite-oxidizing process of nitrification, recovering 30 cycles later at both physiological and kinetic level. The kinetic activity of the nitrifying sludge improved along the operating cycles for both AMP removal and nitrification processes. The elimination of 24% AMP was attributed to the biosorption process and 76% to biotransformation, wherein the AMO enzyme contributed 95% to its biodegradation. Finally, the repeated exposure of the sludge to AMP for 72 operating cycles (36days) was not sufficient to detect β-lactamase activity. The cometabolic ability of ammonium-oxidizing bacteria for biodegrading AMP could be employed for bioremediation of wastewater.

Computational evaluation of micropores wetting effect on the removal process of CO2 through the membrane contactor

In the current years, gas–liquid membrane contactors (GLMCs) have been introduced as a promising, versatile and easy-to-operate technology for mitigating the emission of major greenhouse contaminants (i.e., CO2 and H2S) to the ecosystem. This paper tries to computationally study the role of membrane pores wettability on the removal performance of CO2 inside the HFMC. To fulfill this purpose, a mathematical model based on finite element procedure (FEP) has been employed to solve the momentum and mass transport equations in the partial-wetting (50% wetting of micropores) and non-wetting (0% wetting of micropores) modes of membrane during operation. Additionally, a comprehensive simulation was ensembled to predict the results. In this research, 2-amino-2-methyl-l-propanol (AMP) has been employed as a relatively novel alkanolamine absorbent to separate CO2 form CO2/N2 mixture. Analysis of the results implied that the wetting of membrane micropores significantly deteriorated the removal efficiency due to the enhancing mass transfer resistance towards transferring CO2 (75% in the non-wetting mode > 8% considering 50% wetting of micropores).

Biotic factors shape the structure and dynamics of denitrifying communities within cyanobacterial aggregates.

Eutrophication caused by human activities has severely impacted freshwater ecosystems, leading to harmful cyanobacterial blooms that threaten water quality and ecosystem stability. During blooms, denitrification is a key process for nitrogen removal, which can occur both in the sediment and in the waterbody mediated by cyanobacterial aggregate (CA)-associated microorganisms. In this study, the structure, dynamics and assembly mechanisms of CA-associated nirK-, nirS-, and nosZ-encoding denitrifying communities were investigated in the eutrophic Lake Taihu across the bloom season. External environmental factors showed limited influence on denitrifying community structure, which were more strongly shaped by biotical factors. Network analysis revealed both monofunctional and multifunctional modules, with a small subset of linker OTUs playing a critical role in maintaining these multifunctional modules by mediating interactions among different functional communities. Biotic regulation was further demonstrated by coupling patterns among denitrifiers associated with specific microbial lineages, as well as niche partitioning driven by cyanobacterial composition. While the assembly of the total phycospheric communities was governed by stochastic processes, the denitrifying communities were predominantly shaped by homogeneous selection. These findings indicate biological processes, particularly synergistic relationships and autotroph-heterotroph interactions, were key drivers of the structure and dynamics of denitrifying communities within CAs. Moreover, the key taxa identified in this study may provide potential targets for regulating nitrogen cycling in the management of cyanobacterial blooms.

Application of the Fenton and photo-Fenton processes in pharmaceutical removal: New perspectives in environmental protection

Application of the Fenton and photo-Fenton processes in pharmaceutical removal: New perspectives in environmental protection

Model-based scenario analysis to support the operation of solar photo-Fenton plants.

Model-based tools applied to wastewater management have been identified as an emerging solution to address the associated challenges related to the optimization of the technologies, meeting more restricted water quality standards. Thus, for the first time, the demonstration of the solar photo-Fenton process for microcontaminant removal in the operating environment of a model-based tool is reported. This tool aids in determining the right cost-effective seasonal strategy for a 37-m2 demonstration-scale photoreactor operating in a rural wastewater treatment plant. It was developed using a model tuned adequately with experimental data obtained at lab scale and then validated in the solar photo-Fenton demonstration plant, proving its reliability, and enveloping a robust operation. Imidacloprid removal was the treatment target, and reagent concentrations were 0.1mM for ferric nitrilotriacetate and 0.73mM for hydrogen peroxide. According to the model-based tool, to attain the maximum treatment capacity, the best operating conditions were a liquid depth of 20-cm, and hydraulic residence time of 45 and 60-min in summer and winter, respectively, augmenting the treatment cost by 25% (0.49 €∙m-3 vs. 0.65 €∙m-3). This model-based tool allows the control and optimization of the technology to be improved, while promoting its attractiveness in the market.

The performance of electrocoagulation process for decolorization and COD removal of highly colored real grey water under variable operating conditions

Grey water (GW) reclamation offers a viable solution to address water scarcity. However, the variation in its quality and quantity makes treatment options big challenges. In the last years, Electrocoagulation (EC) has emerged as an effective method for treating GW. This study assessed the performance of a lab-scale EC reactor in treating GW with high concentrations of chemical oxygen demand (COD) and color (1290mg/L and 2540 Pt-CO, respectively), sourced from various origins. The impact of different operational parameters, including electrode material (Iron 'Fe' and Aluminum 'Al'), electrode spacing (1 and 2cm), and current density (5, 10, 15, and 20mA/cm²), was evaluated. Results showed minimal impact from electrode spacing, possibly due to the short electrolysis time (10minutes). However, Al based electrodes outperformed Fe based electrodes, offering reduced health risks from metal contamination. Operating with Al electrodes at a current density of 5mA/cm² led to substantial removal of COD (≥ 82%) and color (≥ 97%) while maintaining low operational costs. This study further supports the viability of EC as an effective method for treating greywater, even at high contaminant levels.

Assessment of hydrogen peroxide, persulfate, and peroxymonosulfate as oxidizing agents in electrochemical oxidation of pyridine

The removal of pyridine, a toxic and refractory nitrogen heterocyclic compound from coal chemical wastewater, has been examined using electrochemical oxidation (EO) processes in the presence of hydrogen peroxide (H2O2), persulfate (PDS), and peroxymonosulfate (PMS). Degradation of pyridine was observed in EO/H2O2, EO/PDS, and EO/PMS systems with removal efficiencies of 41.3, 40.6, and 93.5 %, respectively. The energy consumption for the EO/H2O2, EO/PDS, and EO/PMS processes was calculated to be 1.4, 1.3, and 0.56 KWh g−1, respectively. The yield of ClO3- in the EO/PMS system was relatively higher than that in the EO/PDS system. Additionally, the overall concentration of total organic chlorine was lower in the EO/PDS (292.1 mg/L) and EO/PMS (120.1 mg/L) systems when SO4•– radicals were present. The contribution of reactive species were quantified. Specially, in the EO/H2O2 system, the ratio of OH• was 44 %. In the EO/PDS system, the ratios of OH•, SO4•–, and other reactive species were 31 %, 22 %, and 47 %, respectively. In the EO/PMS system, the ratios of OH•, SO4•–, and other reactive species were 18 %, 71 %, and 11 %, respectively. Specifically, in the EO/PMS system, while CCl3 was detected, no other chlorinated organic intermediates were observed. Compared to EO/H2O2 and EO/PDS systems, the EO/PMS system shows better suitability for high Cl– conditions. The pH had a negligible impact on the EO/H2O2 system. Under acid conditions, degradation rate constants for pyridine were highest in the EO/PMS and EO/PDS systems. Notably, the addition of PMS to coal chemical wastewater achieved a 30 % removal of ultraviolet light absorbance at 254 nm (UV254), indicating effective inhibition of trihalomethane formation. This study provides critical insights into optimizing the EO process for the effective removal of refractory pollutants like pyridine from coal chemical wastewater, enhancing environmental safety and treatment efficiency.

Microbially mediated iron redox processes for carbon and nitrogen removal from wastewater: Recent advances.

Iron is the most abundant redox-active metal on Earth. The microbially mediated iron redox processes, including dissimilatory iron reduction (DIR), ammonium oxidation coupled with Fe(III) reduction (Feammox), Fe(III) dependent anaerobic oxidation of methane (Fe(III)-AOM), nitrate-reducing Fe(II) oxidation (NDFO), and Fe(II) dependent dissimilatory nitrate reduction to ammonium (Fe(II)-DNRA), play important parts in carbon and nitrogen biogeochemical cycling globally. In this review, the reaction mechanisms, electron transfer pathways, functional microorganisms, and characteristics of these processes are summarized; the prospective applications for carbon and nitrogen removal from wastewater are reviewed and discussed; and the research gaps and future directions of these processes for the treatment of wastewater are also underlined. This review is expected to give new insights into the development of economic and environmentally friendly iron-based wastewater treatment procedures.

Computer Aided Brain Tumor Diagnosis using Coati Optimization Algorithm with Explainable Artificial Intelligence Approach

Brain tumors (BT) are a difficult and dangerous medical condition, and the accurate and early analysis of these tumors is crucial for suitable treatment. Explainability in clinical image diagnosis role a vital play in the correct analysis and treatment of tumors that supports medical staff's optimum understanding of the image analysis performances rely upon deep methods. Artificial intelligence (AI), in certain deep neural networks (DNNs) has attained remarkable outcomes for clinical image analysis in many applications. However, the need for explainability of deep neural approaches has been assumed that major restriction before executing these approaches in medical practice. Explainable AI, or XAI, is a vital module in this context as it supports medical staff and patients in understanding the AI's decision-making model, enhancing trust and transparency. It leads to optimum patient care and performance but making sure that medical staff can make learned decisions depends on AI-driven insights. Therefore, this study develops a novel Computer-Aided Brain Tumor Diagnosis using Coati Optimization Algorithm with an Explainable Artificial Intelligence (CABTD-COAXAI) approach. The purpose of the CABTD-COAXAI technique is to exploit XAI and hyperparameter-tuned deep learning (DL) approaches for automated BT analysis. To accomplish this, the CABTD-COAXAI technique follows a Gaussian filtering (GF) based noise removal process. Besides, the CABTD-COAXAI technique utilizes the EfficientNetB7 methods for the feature extraction process. Additionally, the hyperparameter tuning of the EfficientNetB7 method is performed by the use of COA. Furthermore, the classification of the BT process can be performed by the usage of a convolutional autoencoder (CAE). Finally, the CABTD-COAXAI system combines the XAI method named LIME to effectively understand and explainability of the black-box model for automated BT diagnosis. The simulation result of the CABTD-COAXAI technique has been tested on a benchmark BT database. The extensive outcomes inferred that the CABTD-COAXAI method reaches superior performance over other models in terms of different measures

Experimental and ANN based process optimization for bioremediation of Cr6+ and Cd2+ by green adsorbent prepared from Artocarpus Heterophyllus leaves

The effective removal of toxic pollutants from water and waste water, is a challenging issue for environmental protection. In the present work, the performance of Artocarpus Heterophyllus (jackfruit) leaves have been examined for reduction of toxic Cr (VI) and Cd (II) from synthetic wastewater. Characterization of the adsorbent was made to evaluate the surface morphology and chemical composition, by Scanning Electron Micrograph (SEM) and Energy Dispersive Spectroscopy (EDS). Characteristic surface groups [Fourier Transform Infra-Red (FTIR)], surface area and surface structure [Brunauer–Emmett–Teller, (BET)] were also determined. The influences of various factors which control the removal process were studied experimentally in batch method and optimized. High removal efficiency was obtained at pH ≤ 2 for Cr (VI); and for Cd (II) it was ≥ 6. The experimental data were tested using different kinetic and isotherm models. Artocarpus Heterophyllus leaf was found suitable to remove 99.7 % Cr (VI) and 98.4 % Cd (II) from a strength of 20 mg L-1 solution at 0.5 g L-1 adsorbent concentration, at their respective favorable pHs. The reaction followed pseudo second order kinetic model for both the cases. The calculated sorption energy of 16.16 and 12.68 kJ mol-1, suggested chemical nature for both the cases. Desorption studies showed the effective reuse of Artocarpus Heterophyllus leaf for three times. The relatively high equilibrium adsorption capacity of 32.29 and 20.37 mg g-1 for Cr (VI) and Cd (II) respectively, suggested use of Artocarpus Heterophyllus leaf as a reasonably good green bio-adsorbent. The modeling of the complex adsorption process based on artificial neural network approach exhibited reliability and high degree of proficiency (R values of 0.999) in the model’s prediction and experimental data indicated its applicability in forecasting removal efficiency for both the metal ions.

Preparation of CuWO4/CaWO4 n-n heterojunction with enhanced sonocatalytic performance: Characterization, sonocatalytic mechanism and degradation pathways of organic pollutant

In this paper, a novel CuWO4/CaWO4n–n heterojunction was prepared by a hydrothermal method and characterized. Using acid orange 7 (AO7) as simulated dye wastewater, the sonocatalytic performance of CuWO4/CaWO4 composite was investigated. The results suggested that 15 %CuWO4/CaWO4 had the optimum sonocatalytic performance for the removal of AO7. The optimal reaction conditions were as follows: the addition amount of sonocatalyst was 1.0 g/L, the pH value of AO7 was 5, the initial concentration of dye was 5 mg/L, the ultrasonic power was 200 W, the molar ratios of K2S2O8 to AO7 was 70, and the time of ultrasonic irradiation was 120 min, the removal rate of AO7 could reach 93.37 ± 0.76(%). The results showed that the construction of CuWO4/CaWO4 heterojunction could significantly improve the production of active components in the sonocatalytic system, which played an important role in the sonocatalytic removal process of AO7. In addition, the CuWO4/CaWO4 composite catalyst showed good stability. Moreover, the results of AO7 degradation products and their environmental toxicity evaluation showed that the combined use of sonocatalysis and S-AOPs could achieve effective degradation of AO7 and significantly reduced the environmental toxicity of organic pollutants. These results revealed that the CuWO4/CaWO4 composite had potential value in the field of sonocatalysis and provided valuable information for the development of hybrid processes based on sonocatalysis coupled with S-AOPs to remove organic pollutants from wastewater.