Study on Adsorption Properties of Modified Corn Cob Activated Carbon for Mercury Ion

Potassium permanganate-modified eggshell biosorbent for the removal of diclofenac from liquid environment: adsorption performance, isotherm, kinetic, and thermodynamic analyses

This study assess how well diclofenac (DCF) can be separated from aqueous solution using potassium permanganate-modified eggshell biosorbent (MEB). The MEB produced was characterised using XRD, FTIR, and SEM. Batch experiments were conducted to examine and assess the impact of contact time, adsorbent dosage, initial concentration, and temperature on the adsorption capacity of the MEB in the DCF sequestration. The best parameters to obtained 95.64% DCF removal from liquid environment were 0.05 g MEB weight, 50 mg/L initial concentration, and 60 min contact time at room temperature. The maximum DCF sequestration capacity was found to be 159.57 mg/g with 0.05 g of MEB at 298 K. The adsorption isotherm data were more accurately predicted by the Freundlich model, indicating a process of heterogeneous multilayer adsorption. The results of the kinetic study indicated that the pseudo-second-order kinetic models best matched the experimental data. The findings revealed that the dynamic of DCF entrapment is largely chemisorption and diffusion controlled. Based on the values of thermodynamic parameters, the process is both spontaneous and endothermic. The primary processes of DCF sorption mechanism onto the MEB were chemical surface complexation, hydrogen bonding, π-π stacking, and electrostatic interactions. The produced MEB showed effective DCF separation from the aqueous solution and continued to have maximal adsorption capability even after five regeneration cycles. These findings suggest that MEB could be highly efficient adsorbent for the removal of DCF from pharmaceutical wastewater.

Activated Carbon Electrodes for Supercapacitors from Purple Corncob (Zea maysL.)

Activated carbon-based supercapacitor electrodes synthesized from biomass or waste-derived biomass have recently attracted considerable attention because of their low cost, natural abundance, and power delivery performance. In this work, purple-corncob-based active carbons are prepared by KOH activation and subsequently evaluated as a composite electrode for supercapacitors using either an acidic or an alkali solution as the electrolyte. The synthesis of the material involves mixing the purple corncob powder with different concentrations of KOH (in the range of 5% to 30%) and a thermal treatment at 700 °C under an inert atmosphere. Physicochemical characterizations were performed using scanning electron microscopy, Raman spectroscopy, N2 physisorption analysis, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy, while the electrochemical characteristics were determined using cyclic voltammetry, a galvanostatic charge/discharge curve, and electrochemical impedance techniques measured in a three- and two-electrode system. Composite electrodes activated with 10% KOH had a specific surface area of 728 m2 g-1, and high capacitances of 195 F g-1 at 0.5 A g-1 in 1 mol L-1 H2SO4 and 116 F g-1 at 0.5 A g-1 in 1 mol L-1 KOH were obtained. It also presented a 76% capacitance retention after 50 000 cycles. These properties depend significantly on the microporous area and micropore volume characteristics of the activated carbon. Overall, our results indicate that purple corncob has an interesting prospect as a carbon precursor material for supercapacitor electrodes.

Interaction of Naturally Occurring Phytoplankton with the Biogeochemical Cycling of Mercury in Aquatic Environments and Its Effects on Global Hg Pollution and Public Health

The biogeochemical cycling of mercury in aquatic environments is a complex process driven by various factors, such as ambient temperature, seasonal variations, methylating bacteria activity, dissolved oxygen levels, and Hg interaction with dissolved organic matter (DOM). As a consequence, part of the Hg contamination from anthropogenic activity that was buried in sediments is reinserted into water columns mainly in highly toxic organic Hg forms (methylmercury, dimethylmercury, etc.). This is especially prominent in the coastal shallow waters of industrial regions worldwide. The main entrance point of these highly toxic Hg forms in the aquatic food web is the naturally occurring phytoplankton. Hg availability, intake, effect on population size, cell toxicity, eventual biotransformation, and intracellular stability in phytoplankton are of the greatest importance for human health, having in mind that such Hg incorporated inside the phytoplankton cells due to biomagnification effects eventually ends up in aquatic wildlife, fish, seafood, and in the human diet. This review summarizes recent findings on the topic of organic Hg form interaction with natural phytoplankton and offers new insight into the matter with possible directions of future research for the prevention of Hg biomagnification in the scope of climate change and global pollution increase scenarios.

Effects of different concentrations of butyrate on microbial community construction and metabolic pathways in anaerobic digestion

Investigating the effect of butyric acid concentration on anaerobic digestion systems in complex systems is important for the efficient degradation of butyric acid and improving the efficiency of anaerobic digestion. In this study, different loadings of butyric acid with 2.8, 3.2, and 3.6 g/(L·d) were added to the anaerobic reactor. At a high organic loading rate of 3.6 g/(L·d), methane was efficiently produced with VBP (Volumetric Biogas Production) of 1.50 L/(L·d) and biogas content between 65% and 75%. VFAs concentration remained below 2000 mg/L. Metagenome sequencing revealed changes in the functional flora within different stages. Methanosarcina, Syntrophomonas, and Lentimicrobium were the main and functional microorganisms. That the relative abundance of methanogens exceeded 35% and methanogenic metabolic pathways were increased indicated the methanogenic capacity of the system significantly improved. The presence of a large number of hydrolytic acid-producing bacteria also indicated the importance of the hydrolytic acid-producing stage in the system.

Study on Efficient Adsorption Mechanism of Pb2+ by Magnetic Coconut Biochar

Lead ion (Pb²⁺) in wastewater cannot be biodegraded and destroyed. It can easily be enriched in living organisms, which causes serious harm to the environment and human health. Among the existing treatment technologies, adsorption is a green and efficient way to treat heavy metal contamination. Novel KMnO₄-treated magnetic biochar (KFBC) was successfully synthesized by the addition of Fe(NO₃)₃ and KMnO₄ treatment during carbonization following Pb²⁺ adsorption. SEM-EDS, XPS, and ICP-OES were used to evaluate the KFBC and magnetic biochar (FBC) on the surface morphology, surface chemistry characteristics, surface functional groups, and Pb²⁺ adsorption behavior. The effects of pH on the Pb²⁺ solution, initial concentration of Pb²⁺, adsorption time, and influencing ions on the adsorption amount of Pb²⁺ were examined, and the adsorption mechanisms of FBC and KFBC on Pb²⁺ were investigated. The results showed that pH had a strong influence on the adsorption of KFBC and the optimum adsorption pH was 5. The saturation adsorption capacity fitted by the model was 170.668 mg/g. The successful loading of manganese oxides and the enhanced oxygen functional groups, as evidenced by XPS and FTIR data, improved KFBC for heavy metal adsorption. Mineral precipitation, functional group complexation, and π-electron interactions were the primary adsorption processes.

Manganese oxide-modified biochar: production, characterization and applications for the removal of pollutants from aqueous environments - a review

The development of manganese (Mn) oxides (MnOx) modified biochar (MnOBC) for the removal of pollutants from water has received significant attention. However, a comprehensive review focusing on the use of MnOBC for the removal of organic and inorganic pollutants from water is missing. Therefore, the preparation and characterization of MnOBC, and its capacity for the removal of inorganic (e.g., toxic elements) and organic (e.g., antibiotics and dyes) from water have been discussed in relation to feedstock properties, pyrolysis temperature, modification ratio, and environmental conditions here. The removal mechanisms of pollutants by MnOBC and the fate of the sorbed pollutants onto MnOBC have been reviewed. The impregnation of biochar with MnOx improved its surface morphology, functional group modification, and elemental composition, and thus increased its sorption capacity. This review establishes a comprehensive understanding of synthesizing and using MnOBC as an effective biosorbent for remediation of contaminated aqueous environments.