Recovery of Cr(III) by using chars from the co-gasification of agriculture and forestry wastes

Interactive effects of soil moisture and temperature on chromium-induced microbial and enzymatic stress

Climatic conditions play a critical role in soil health, as changes in temperature and moisture directly impact soil microbial populations. The presence of potentially toxic elements, particularly chromium (Cr), poses a significant threat to microbial communities and can alter soil chemical properties. Current study investigated the effects of Cr toxicity under varying soil volumetric water contents (30% and 40%) and temperature (25 °C and 40 °C) on microbial biomass and enzyme activities. The experiment was conducted over 60 days with six Cr levels: control, 50, 100, 150, 200, and 250 mg Cr kg-1 soil. Results revealed a significant reduction in soil microbial biomass carbon, nitrogen, phosphorus, and sulfur at Cr contamination levels above 100 mg kg-1. Specifically, at 30% soil moisture and 25 °C, microbial biomass carbon, nitrogen, phosphorus, and sulfur were reduced by 59.09, 66.72, 50.82, and 61.03%, respectively. At 40% soil moisture and 40 °C, reductions were recorded 23.77, 46.95, 48.83, and 30.87%, respectively. Additionally, soil enzyme activities declined with increasing Cr levels. Amidase, urease, alkaline phosphatase, β-glucosidase, arylsulfatase, and dehydrogenase activities decreased to 47.98, 50.41, 50.32, 64.34, 46.64, and 48.49% at 30% soil moisture and 25 °C, respectively. At 40% soil moisture and 40 °C, reductions were calculated 32.90, 37.09, 45.39, 55.71, 38.37, and 36.76%, respectively. The findings indicate that chromium contamination and changes in soil moisture and temperature significantly compromise soil microbial biomass and enzyme activities. This study highlights the need for monitoring and mitigating Cr contamination to maintain soil biological health and overall ecosystem functionality.

Recent advances in valorization of lignocellulosic waste into biochar and its functionalization for the removal of chromium ions

Lignocellulosic waste is a prevalent byproduct of agricultural and forestry activities which is an excellent feedstock for the preparation of biochar. This research area is of interest to the scientific community due to its potential in environmental remediation. In this regard, this review examines the latest advancements in transforming lignocellulosic waste into biochar and explores recent innovations in enhancing its functionality for chromium ion removal. It gives analysis on current methods for biochar production from lignocellulosic materials such as pyrolysis. Additionally focusing on improvements in production efficiency, structural properties, and surface modifications. The review also highlights various functionalization techniques, such as chemical activation and impregnation with metal oxides, that were innovated to improve adsorptive nature of biochar for chromium ions. While progress has been made, achieving scalability in lignocellulosic biochar production presents challenges, such as the high energy demands of pyrolysis, inconsistencies in feedstock quality, and the need for cost-effective functionalization methods. By summarizing recent research and technological progress, this paper aims to offer a clear perspective on the effectiveness of biochar derived from lignocellulosic waste in addressing contamination. Additionally, it discusses the ongoing challenges and future research directions needed to optimize biochar applications in environmental cleanup.

Utilization of biochar for remediation of heavy metals in aqueous environments: A review and bibliometric analysis

Biochar usage for removing heavy metals from aqueous environments has emerged as a promising research area with significant environmental and economic benefits. Using the PICO approach, the research question aimed to explore using biochar to remove heavy metals from aqueous media. We merged the data from Scopus and the Web of Science Core Collection databases to acquire a comprehensive perspective of the subject. The PRISMA guidelines were applied to establish the search parameters, identify the appropriate articles, and collect the bibliographic information from the publications between 2010 and 2022. The bibliometric analysis showed that biochar-based heavy metal remediation is a research field with increasing scholarly attention. The removal of Cr(VI), Pb(II), Cd(II), and Cu(II) was the most studied among the heavy metals. We identified five main clusters centered on adsorption, water treatment, adsorption models, analytical techniques, and hydrothermal carbonization by performing keyword co-occurrence analysis. Trending topics include biochar reusability, modification, acid mine drainage (AMD), wastewater treatment, and hydrochar. The reutilization of heavy metal-loaded spent biochar includes transforming it into electrodes for supercapacitors or stable catalyst materials. This study provides a comprehensive overview of biochar-based heavy metal remediation in aquatic environments and highlights knowledge gaps and future research directions.