Mechanochemical modified nitrogen-rich biochar derived from shrimp shell: Dominant mechanism in pyridinic-N for aquatic methylene blue removal

ZIF-67 and Biomass-Derived N, S-Codoped Activated Carbon Composite Derivative for High-Effective Removal of Hydroquinone from Water

Hydroquinone (HQ) in wastewater is of great concern, as it is harmful to human health and threatens the ecological environment. However, the existing adsorbents have low adsorption capacity for HQ. To improve the removal of HQ, N,S-codoped activated carbon-ZIF-67 (NSAC-ZIF-67@C) was synthesized in this study by in situ growth of ZIF-67 on N,S-codoped activated carbon (NSAC) and carbonization. The influence of pH, contact time, and initial concentration on the adsorption behaviors of NSAC-ZIF-67@C on HQ were investigated. Owing to the synergistic effect of abundant active sites and well-developed pore structure, the NSAC-ZIF-67@C achieved a prominent adsorption capacity of 962 mg·g-1 and can still retain high adsorption performance after 5 cycles for HQ, which is superior to that of reported other adsorbents. HQ adsorption follows the pseudo-second-order kinetics model (R2 = 0.99999) and the Freundlich isotherm model. X-ray photoelectron spectroscopy (XPS) analysis before and after adsorption as well as density functional theory (DFT) calculation results showed that pyridinic-N-termini were conducive to the π-π interactions and hydrogen-bonding interactions. Therefore, the adsorption mechanisms of NSAC-ZIF-67@C on HQ involve pore filling, electrostatic attraction, π-π interaction, and hydrogen bonding. This study is expected to provide a reference for designing highly effective adsorbents for wastewater treatment.

Pristine and modified biochar applications as multifunctional component towards sustainable future: Recent advances and new insights

Employing biomass for environmental conservation is regarded as a successful and environmentally friendly technique since they are cost-effective, renewable, and abundant. Biochar (BC), a thermochemically converted biomass, has a considerably lower production cost than the other conventional activated carbons. This material's distinctive properties, including a high carbon content, good electrical conductivity (EC), high stability, and a large surface area, can be utilized in various research fields. BC is feasible as a renewable source for potential applications that may achieve a comprehensive economic niche. Despite being an inexpensive and environmentally sustainable product, research has indicated that pristine BC possesses restricted properties that prevent it from fulfilling the intended remediation objectives. Consequently, modifications must be made to BC to strengthen its physicochemical properties and, thereby, its efficacy in decontaminating the environment. Modified BC, an enhanced iteration of BC, has garnered considerable interest within academia. Many modification techniques have been suggested to augment BC's functionality, including its adsorption and immobilization reliability. Modified BC is overviewed in its production, functionality, applications, and regeneration. This work provides a holistic review of the recent advances in synthesizing modified BC through physical, chemical, or biological methods to achieve enhanced performance in a specific application, which has generated considerable research interest. Surface chemistry modifications require the initiation of surface functional groups, which can be accomplished through various techniques. Therefore, the fundamental objective of these modification techniques is to improve the efficacy of BC contaminant removal, typically through adjustments in its physical or chemical characteristics, including surface area or functionality. In addition, this article summarized and discussed the applications and related mechanisms of modified BC in environmental decontamination, focusing on applying it as an ideal adsorbent, soil amendment, catalyst, electrochemical device, and anaerobic digestion (AD) promoter. Current research trends, future directions, and academic demands were available in this study.

Release of biochar-derived dissolved organic matter and the formation of chlorination disinfection by-products: Effects of pH and chlorine dosage

Transformation, fragmentation, dissolution, and oxidation of biochar are inevitable in the environment, which will undoubtedly accelerate the release of biochar-derived dissolved organic matter (BDOM) into various water bodies. In addition, biochar may affect disinfection by-products (DBPs) during water treatment and subsequent disinfection. In this study, biochars were derived at three selected pyrolysis temperatures (350 °C, 500 °C, and 650 °C) from rice husk, wheat straw, and shrimp shell, and BDOM was extracted from biochar-derived in artificial seawater and ultrapure water. The TOC analyzer results showed that the concentrations of three BDOM decreased with increasing pyrolysis temperature. The BDOM derived from rice husk biochar and wheat straw biochar in seawater was lower than that in ultrapure water, while that of shrimp shell biochar showed an opposite trend, being released in seawater at nearly twice the extent of that in ultrapure water at 350 °C. Moreover, BDOM showed a catalytic effect on chlorination, and GC analysis showed that the concentrations of its DBPs were affected by pH. The concentration of halogenated acetic acid reached the highest value (54.51 μg/L) in weak acidic environment, while the concentrations of trihalomethane and halogenated acetonitrile had the highest values (23.63 and 47.53 μg/L, respectively) in alkaline conditions. The concentrations of all the three DBPs were lowest under neutral pH conditions. In addition, the volatile halogenated DBPs such as dichloroacetone and trichloroacetone were easily hydrolyzed under alkaline conditions. Therefore, it is something be aware of the release of BDOM and the effects of chlorination DBPs when biochar is used for water treatment or water purification.

Effect of different production methods on physicochemical properties and adsorption capacities of biochar from sewage sludge and kitchen waste: Mechanism and correlation analysis

Different pyrolysis methods, parameters and feedstocks result in biochars with different properties, structures and removal capacities for heavy metals. However, the role of each property on adsorption capacity and corresponding causal relationships remain unclear. Here, we investigated various physicochemical properties of biochar produced via three different methods and two different feedstocks to clarify influences of biomass sources and pyrolysis processes on biochar properties and its heavy metal adsorption performance. Experimental results showed biochars were more aromatic and contained more functional groups after hydrothermal carbonization, while they had developed pores and higher surface areas produced by anaerobic pyrolysis. The inclusion of oxygen resulted in more complete carbonization and higher CEC biochar. Different biochar properties resulted in different adsorption capacities. Biochar produced by aerobic calcination showed higher adsorption efficiency for Cu and Pb. Correlation analysis proved that pH, cation exchange capacity and degree of carbonization positively affected adsorption, while organic matter content and aromaticity were unfavorable for adsorption. Microstructure and components determined biochar macroscopic properties and ultimate adsorption efficiency for metal ions. This study identifies the degree of correlation and pathways of each property on adsorption, which provides guidance for targeted modification of biochar to enhance its performance in heavy metal removal.

Biochar preparation and evaluation of its effect in composting mechanism: A review

This article provides an overview of biochar application for organic waste co-composting and its biochemical transformation mechanism. As a composting amendment, biochar work in the adsorption of nutrients, the retention of oxygen and water, and the promotion of electron transfer. These functions serve the micro-organisms (physical support of niche) and determine changes in community structure beyond the succession of composing primary microorganisms. Biochar mediates resistance genes, mobile gene elements, and biochemical metabolic activities of organic matter degrading. The participation of biochar enriched the α-diversity of microbial communities at all stages of composting, and ultimately reflects the high γ-diversity. Finally, easy and convincing biochar preparation methods and characteristic need to be explored, in turn, the mechanism of biochar on composting microbes at the microscopic level can be studied in depth.