Burkholderia cepacia immobilized on eucalyptus leaves used to simultaneously remove malachite green (MG) and Cr(VI)

Bionanocomposite based on immobilization of Burkholderia cepacian on GO/MOF and its removal of malachite green from river water

Bio-nanocomposites have attracted increasing research attention because they are able to integrate bio- and nano-related functions, and subsequently demonstrate potentially beneficial environmental applications. Here, a functional bionanomaterial based on Burkholderia cepacian (FZ) immobilized on GO/ZIF-8 was developed and used to remove malachite green (MG), with functions based on both biodegradation and adsorption. XRD and FTIR results showed that in situ production of GO/ZIF-8 by combining Zn2+ in ZIF-8 with the carboxyl group on the GO surface, led to FZ immobilized in GO/ZIF-8 through covalent bonding. Zeta analysis showed that the surface of FZ and GO/ZIF-8 had different charges under pH = 9.12, suggesting immobilization also occurred via electrostatic action. BET results confirmed that the specific surface area of GO/ZIF-8 was much larger than that of GO and ZIF-8, but the reduced specific surface area of FZ@GO/ZIF-8 could be due to FZ loading on its surface. The efficiency of FZ@GO/ZIF-8 in the removal of MG reached 99% and furthermore retained good stability after five cycles. The efficiency in removing multiple ions in river water reached more than 80%, which is evidence strongly suggesting that FZ@GO/ZIF-8 is an environmental bionanomaterial with effective application potential.

Decolorization potential of malachite green by Ralstonia mannitolilytica isolated from Indonesian cassava-based fermented food tapai

Pollution due to textile dye effluent mishandling is hazardous to ecosystems and to the living beings inhabiting them. This can cause retarded photosynthesis, disrupted fish day/night cycles, unbalanced bacterial populations, and decreased oxygen concentration in contaminated water, leading to low habitability. In this study, we aimed to isolate and characterize the microorganisms found in Indonesian cassava-based fermented food tapai starter cultures as a source of potential microbes for the biological remediation of textile dye pollutants. Microorganisms in the tapai starter culture were screened for their decolorization activity via spread-culture inoculation on a solid growth medium supplemented with textile dyes. Isolated microorganisms were selected based on their ability to secrete textile dye-decolorizing extracellular enzymes via increased light penetration after incubation of the cell-free supernatant (CFS) containing extracellular enzymes in textile dye solutions. Isolate JSP1 was the only bacterium capable of producing malachite green (MG)-decolorizing extracellular enzymes, which enabled it to survive and decolorize MG up to 375 ppm. Moreover, isolate JSP1 CFS was able to optimally decolorize 75% of MG at 100 ppm, but its activity was diminished at concentrations > 350 ppm. Colony and cellular morphology, biochemistry, and 16S rRNA tests revealed that the isolate was of Ralstonia mannitolilytica. Therefore, R. mannitolilytica isolate JSP1 may be a potential bioremediation agent for MG.

Enhanced treatment of landfill leachate by biochar-based aerobic denitrifying bacteria functional microbial materials: Preparation and performance

Objective

In this work, polyvinyl alcohol (PVA) and sodium alginate (SA) were used as entrapped carriers and Artemisia argyi stem biochar (ABC) was used as an absorption carrier to immobilize aerobic denitrifying bacteria screened from landfill leachate, thus a new carbon-based functional microbial material (PVA/SA/ABC@BS) was successfully prepared.

Methods

The structure and characteristics of the new material were revealed by using a scanning electron microscope and Fourier transform infrared spectroscopy, and the performance of the material for treating landfill leachate under different working conditions was studied.

Results

ABC had abundant pore structures and that the surface contained many oxygen-containing functional groups, carboxyl groups, and amide groups, etc. and it had good absorbing performance and strong acid and alkali buffering capacity, which was beneficial to the adhesion and proliferation of microorganisms. After adding ABC as a composite carrier, the damage rate of immobilized particles was decreased by 1.2%, and the acid stability, alkaline stability, and mass transfer performance were increased by 9.00, 7.00, and 56%, respectively. When the dosage of PVA/SA/ABC@BS was 0.017g/ml, the removal rates of nitrate nitrogen (NO₃ ^--N) and ammonia nitrogen (NH₄ ⁺-N) were the highest, which were 98.7 and 59.4%, respectively. When the pH values were 11, 7, 1, and 9, the removal rates of chemical oxygen demand (COD), NO₃ ^--N, nitrite nitrogen (NO₂ ^--N) and NH₄ ⁺-N reached the maximum values, which were 14.39, 98.38, 75.87, and 79.31%, respectively. After PVA/SA/ABC@BS was reused in 5 batches, the removal rates of NO₃ ^--N all reached 95.50%.

Conclusion

PVA, SA and ABC have excellent reusability for immobilization of microorganisms and degradation of nitrate nitrogen. This study can provide some guidance for the great application potential of immobilized gel spheres in the treatment of high concentration organic wastewater.

Oleic Acid Facilitates Cd Excretion by Increasing the Abundance of Burkholderia in Cd-Exposed Mice

As a global pollutant, cadmium (Cd) can easily enter the body through food chains, threatening human health. Most Cd is initially absorbed in the gut, with the gut microbiota playing a pivotal role in reducing Cd absorption and accumulation. This study assessed the effects of three fatty acids on Cd accumulation and toxicity in Cd-exposed mice. The results showed that oleic acid (OA) was the most effective in facilitating Cd excretion in mice among these fatty acids. The use of OA led to reduced Cd accumulation in the organs and increased Cd content in the feces. The metagenomic analysis of the gut microbiota showed that the genus Burkholderia was the most significantly restored by OA in Cd-exposed mice. Burkholderia cepacia, as the type species for the genus Burkholderia, also exhibited strong Cd tolerance after treatment with OA. Furthermore, the electron microscopy analysis showed that most of the Cd was adsorbed on the surface of B. cepacia, where the extracellular polymeric substances (EPSs) secreted by B. cepacia play a key role, displaying a strong capacity for Cd adsorption. The peak at 2355 cm^-1 and the total sulfhydryl group content of EPSs showed significant increases following co-treatment with Cd and OA. The results demonstrated the potential roles that gut Burkholderia may play in OA-mediated Cd excretion in mice.

Bi-model cationic dye adsorption by native and surface-modified Trichoderma asperellum BPL MBT1 biomass: From fermentation waste to value-added biosorbent

In this study, we aimed to assess the possible reusability of native and surface-modified waste biomass of a novel ascomycetes fungi Trichoderma asperellum BPL MBT1 for the adsorption of triphenylmethane dyes. Spent biomass obtained from fermentation medium has been applied in the uptake of model cationic dyes viz., crystal violet and malachite green. Optimization of experimental parameters by batch mode studies revealed that dye adsorption is influenced by medium pH time, initial concentration of dyes, and adsorbent dosage. It was observed that pH 10 was optimum for cationic dye adsorption. Further, the adsorption process obeyed the bi-model (Langmuir-Freundlich model) isotherm and adhered to pseudo-second-order kinetics. The involvement of ion exchange as the dominant mechanism of dye adsorption was indicated by the mean free energy obtained from Dubinin-Radushkevich isotherm. Cellular morphology and the involved functional groups were studied by scanning electron microscopy and Fourier transform infrared spectroscopy that revealed the presence of carbon and oxygen containing groups on the surface. Maximum desorption efficiency was achieved using a 0.1 M solution of HCl and the stability of the biosorbent was confirmed through reusability analysis. Our results confirm the applicability of both native and surface-modified T. asperellum BPL MBT1 biomass as a potential biosorbent for the sustainable wastewater treatment and safe dye disposal.

Remediation of malachite green in wastewater by ZIF-8@Fe/Ni nanoparticles based on adsorption and reduction

Dye-contaminated wastewater resulting from rapid industrialization and urbanization is a global problem. In this study, a ZIF-8@Fe/Ni sample was synthesized for the removal of malachite green (MG), removing more than 99% of an initial MG concentration of 50 mg L^-1 within 120 min with a 318 K adsorption capacity of 151.520 mg g^-1. To understand the dye removal mechanism based on adsorption and reduction, ZIF-8@Fe/Ni was characterized by various techniques. XRD showed that the ZIF-8@Fe/Ni composite had a characteristic peak attributable to Fe/Ni around 44.8°, where the presence of Fe/Ni did not affect the structure of ZIF-8. SEM confirmed that ZIF-8@Fe/Ni was successfully prepared, while XRD and FTIR revealed that the structure of ZIF-8@Fe/Ni remained stable following the introduction of Fe/Ni. XPS showed that while Fe/Ni nanoparticles existed in ZIF-8-Fe/Ni, partial oxidation also occurred. GC-MS demonstrated the creation of two major MG degradation products, (4-aminophenyl) (phenyl) methanone and 4-aminophenol. While the overall adsorption process of MG to ZIF-8@Fe/Ni conformed to pseudo-second-order kinetics, degradation followed pseudo-first-order reduction kinetics. When applied to the remediation of wastewater, ZIF-8@Fe/Ni removed 92% of MG. Overall, this study demonstrated that ZIF-8@Fe/Ni could be a promising material for the treatment of wastewater.

Adsorptive Removal of Malachite Green Dye onto Coal-Associated Soil and Conditions Optimization

The present research was investigated to eliminate the cationic dye (malachite green (MG)) from the water environment using coal-associated soil. The adsorbent material was characterized using scanning electron microscopy (SEM) and Fourier Transform Infrared Spectrophotometer (FTIR) analyses. Batch experiments were performed to investigate the different factors which affect the adsorption study. The maximum percentage removal of MG dye was attained as follows: adsorbent dose of 1.0 g/L (0.2 to 1.6 g/L), solution pH of 6.0 (2.0 to 9.0), temperature of 30°C (30 to 60°C), time contact of 60min (10 to 90 min), and dye’s concentration of 25 mg/L (25 to 150 mg/L). The adsorption isotherm was studied with four different isotherm models and results showed that the Freundlich isotherm model gave the best fit than the other nonlinear models to designate the isotherm behaviours with $R^2$ value of 0.9568, and the maximum adsorption capacity of coal-associated soil for MG dye adsorption is 89.97 mg/g. The evaluation of kinetic studies was performed by using three different kinetic models, where it exposed that pseudofirst order providing the best fit with $R^2$ value of 0.96 (25 to 150 mg/L). The thermodynamic parameters Gibbs free energy (ΔG°), entropy (ΔS°), and enthalpy (ΔH°) were endorsing that the present adsorption system was exothermic. Thus, the experimental results state that coal-associated soil could be an alternative material for the exclusion of dyes from water.

Decolorization of water through removal of methylene blue and malachite green on biodegradable magnetic Bauhinia variagata fruits

Batch sorption experiments were performed to investigate the potential of Bauhinia variagata fruit (BVf) and nano-magnetic Bauhinia variagata fruit (nM-BVf) to remove methylene blue (MB) and malachite green (MG). Equilibrium studies have been carried out using various experimental parameters such as the amount of biosorbent, initial solution concentration, contact time, pH, and temperature. The Langmuir, Freundlich, Scatchard, D-R and Temkin adsorption models were applied for the experimental information of MB and MG. The Freundlich model fits better than the Langmuir model. Freundlich model confirmed the magnificent dye sorption ability; 19.3 mg/g for BVf/MB, 21.2 mg/g for nM-BVf/MB, 19.7 mg/g for BVf/MG, and 30.1 mg/g for nM-BVf/MG. The pseudo-second-order kinetic model displayed a more suitable behavior to the experimental result for the removal of MG and MB. Thermodynamic parameters such as changes in Gibbs free energy (ΔG^o), enthalpy (ΔH^o), and entropy (ΔS^o) were investigated and the fine details in the adsorption system were completed. The conclusion from this study is that the prepared nano biosorbent can be efficient for the removal of cationic dyes from wastewater.

An efficient Egeria najas-derived biochar supported nZVI composite for Cr(VI) removal: Characterization and mechanism investigation based on visual MINTEQ model

Egeria najas is a submerged aquatic plant, and the literatures on resourcification of submerged aquatic plant biochar remain limited. Until now, there has been no study on submerged aquatic plant biochar supported nZVI that is widely applied for removal of diversified contaminants in solution. In this study, an efficient approach to the preparation of Egeria najas-derived biochar supported nZVI composite is first developed for Cr(VI) removal in wastewater. The adsorption behavior and mechanism of Cr(VI) removal on the as-prepared Egeria najas-derived biochar/nZVI (EN@nZVI) composite were investigated. The results of FTIR and XPS indicate that the EN@nZVI surface had many functional groups such as R-COOH, R-OH, R-NH₂ and R-C-O-C, etc, which could provide active sites during the adsorption process. The BET results showed that the EN@nZVI had large specific surface area and average pore, which were 142.49 m²/g and 9.85 nm, respectively. EN@nZVI demonstrated high reactivity for Cr(VI) removal. Compared with nZVI, Cr(VI) removal efficiency by EN@nZVI is 50% higher than that of nZVI within 0.5 h. Furthermore, the maximum adsorption capacity of Cr (VI) was 56.79 mg/g and the energy of activation (E_a) was 31.30 kJ/mol. The adsorption process was well described by the pseudo-second order model and Sips adsorption isotherm model. The reaction mechanism of Cr(VI) removal was a multi-step removal mechanism, involving adsorption, surface complex formation, reduction and ion exchange reaction.

Synergy of Photocatalysis and Adsorption for Simultaneous Removal of Hexavalent Chromium and Methylene Blue by g-C3N4/BiFeO3/Carbon Nanotubes Ternary Composites

A novel graphite-phase carbon nitride (g-C₃N₄)/bismuth ferrite (BiFeO₃)/carbon nanotubes (CNTs) ternary magnetic composite (CNBT) was prepared by a hydrothermal synthesis. Using this material, Cr(VI) and methylene blue (MB) were removed from wastewater through synergistic adsorption and photocatalysis. The effects of pH, time, and pollutant concentration on the photocatalytic performance of CNBT, as well as possible interactions between Cr(VI) and MB species were analyzed. The obtained results showed that CNTs could effectively reduce the recombination rate of electron-hole pairs during the photocatalytic reaction of the g-C₃N₄/BiFeO₃ composite, thereby improving its photocatalytic performance, while the presence of MB increased the reduction rate of Cr(VI). After 5 h of the simultaneous adsorption and photocatalysis by CNBT, the removal rates of Cr(VI) and MB were 93% and 98%, respectively. This study provides a new theoretical basis and technical guidance for the combined application of photocatalysis and adsorption in the treatment of wastewaters containing mixed pollutants.