Search

As one of the most common ways to get rid of municipal waste, landfill leachate, waste with complicated compositions and high levels of contaminants, has become a significant threat to the world's environment. Here, the impact of sewage sludge (SS) and derived-biochar (SSB) amendments on the immobilization and potential mobility of heavy metals in a contaminated soil-plant system was investigated. The sequential fractionation findings showed that using SS-2%, SSB-2%, and SSBC-1% reduced the potential mobility of heavy metals while increasing the residual fraction in polluted soils. The translocation and bioconcentration factors showed that heavy metals were slightly transferred into shoots from roots and lowered accumulation in roots from contaminated soils. Fourier transform infrared (FTIR) and X-ray photoelectron spectrum (XPS) comprehensive characterization results indicated the significant role of applied amendments for heavy metals transformation from the exchangeable-soluble fractions to the least available form by lowering their mobility to confirm the adsorption-based complexes, which results in the surface adsorption of heavy metals with functional groups. The electron paramagnetic resonance (EPR) results indicated the dominance of reactive oxygen species (ROS) in the intracellular formation of hydroxyl radicals (•OH) in maize plant roots and shoots. ROS (•OH) generation plays a critical influence in the interaction between the physiological processes of plants and heavy metals. Moreover, all the amendments increased maize growth and biomass production. Our study suggests that alone and combined application of SS and SSB have great potential to remediate heavy metals contaminated soil for environmental sustainability. [Display omitted] • SS and SSB efficiently alleviated heavy metals contamination in soil-plant system. • SS and SSB resulted in the surface adsorption of heavy metals with functional moieties. • Amendments decreased the exchangeable-soluble fraction of heavy metals in soil. • Intracellular •OH formation in plants under metal contamination was elucidated. • Heavy metal speciation and mobilization in soil-plant systems were revealed. [ABSTRACT FROM AUTHOR]

The purpose of this research was to examine the influence of hydrothermally treated coal gangue (HTCG) with and without biochar (BC) on the leaching, bioavailability, and redistribution of chemical fractions of heavy metals (HMs) in copper mine tailing (Cu-MT). An increase in pH, water holding capacity (WHC) and soil organic carbon (SOC) were observed due to the addition of BC in combination with raw coal gangue (RCG) and HTCG. A high Cu and other HMs concentration in pore water (PW) and amended Cu-MT were reduced by the combination of BC with RCG and/or HTCG, whereas individual application of RCG slightly increased the Cu, Cd, and Zn leaching and bioavailability, compared to the unamended Cu-MT. Sequential extractions results showed a reduction in the exchangeable fraction of Cu, Cd, Pb, and Zn and elevation in the residual fraction following the addition of BC-2% and BC-HTCG. However, individual application of RCG slightly increased the Cu, Cd, and Zn exchangeable fractions assessed by chemical extraction method. Rapeseed was grown for the following 45 days during which physiological parameters, metal uptake transfer rate (TR), bioconcentration factor (BCF), and translocation factor (TF) were measured after harvesting. In the case of plant biomass, no significant difference between applied amendments was observed for the fresh biomass (FBM) and dry biomass (DBM) of shoots and roots of rapeseed. However, BC-2% and BC-HTCG presented the lowest HMs uptake, TR, BCF (BCF root and BCF shoot), and TF for Cu, Cd, Cr, Ni, Pb, and Zn in rapeseed among the other amendments compared to the unamended Cu-MT. Overall, these findings are indicative that using biochar in combination with RCG and/or HTCG led to a larger reduction in HMs leaching and bioavailability, due to their higher sorption capacity and could be a suitable remediation strategy for heavy metals in a Cu-MT. Image 1 • Biochar and hydrothermally treated coal gangue reduced metals leaching due to surface functionalization and complexation. • Metal uptake was reduced with the application of biochar and hydrothermally treated coal gangue. • Combined application influenced transfer rate in plant by metal stabilization process. [ABSTRACT FROM AUTHOR]

Rapid industrialization and urbanization have resulted in the widespread contamination of soil by potentially toxic metal(loid)s (PTMs). Among these, arsenic (As), cadmium (Cd), chromium (Cr) lead (Pb) and nickel (Ni) are particularly concerning, affecting millions of hectares of arable land globally and posing significant threats to food security and human health. Biochar (BC) has emerged as a promising soil amendment due to its ability to mitigate soil pollution by immobilizing contaminants. But how biochar-linked free radicals affect this process in plants and soil remains murky. Additionally, the mechanism of the geochemical transformation of PTMs in soil-plant systems influenced by biochar-based free radicals is unclear. Here, the influence of free radicals on immobilization, and transformation of PTMs in the soil-plant system under various BC and Comp treatment was investigated. Six treatment groups (1% and 2% biochar, compost, combined application, and control) were randomly assigned to pots in a randomized complete block design (RCBD) to test their effects on maize growth. Results revealed that there was a noticeable rise in the concentration of free radicals in both the BC and Comp treatments compared to the control and the combined application of BC and Comp treatments. The biochar treatment showed a slight reduction in these functional groups, suggesting possible adsorption or sequestration onto the BC surface while the Comp treatment led to an increase in functional groups associated with carbohydrates, proteins, and lipids, indicating enhanced organic matter content. The combined treatment exhibited intermediate effects, suggesting a synergistic interaction between Comp and biochar. X-ray diffraction analysis indicated that the BC did not demonstrate significant alterations in soil mineralogy, suggesting minimal direct effects on mineral dissolution or transformation. Conclusively, biochar-generated free radicals, especially hydroxyl radicals (•OH), play a crucial role in PTMs (i.e., Cd, Cr, Ni, As and Pb) immobilization in soil-plant systems. This study provides novel insights into biochar's mechanisms for mitigating PTMs pollution, paving the way for optimized soil amendment strategies. • BC and Comp influence free radicals generation in the soil-plant system. • BC & Comp treatments affect maize growth influence PTMs availability. • BC-based free radicals play a pivotal role in the geochemical transformation of PTMs. • Reveals distinct effects of BC and Comp amendments on soil functional groups. • BC and Comp demonstrate synergistic effects on FR generation and PTM transformation. [ABSTRACT FROM AUTHOR]

Abstract A series of new biochar-supported composite based on the combination of biochar and metallic nanoparticles (NPs) were produced through single-step pyrolysis of FeCl 3 –Ti(OBu) 4 laden agar biomass under NH 3 environment. The physiochemical properties of composites were characterized thoroughly. It has found that heating temperature and N-doping through NH 3 -ambiance pyrolysis significantly influence the visible-light sensitivity and bandgap energy of composites. The catalytic activities of composites were measured by degradation of Methylene Blue (MB) in the presence or absence of H 2 O 2 and visible-light irradiation. Our best catalyst (N–TiO 2 –Fe 3 O 4 -biochar) exhibits rapid and high MB removal competency (99.99%) via synergism of adsorption, photodegradation, and Fenton-like reaction. Continuous production of O 2 − and OH radicles performs MB degradation and mineralization, confirmed by scavenging experiments and degradation product analysis. The local trap state Ti3 +, Fe 3 O 4 , and N-carbon of the catalyst acted as active sites. It has suggested that the Ti3 + and N-doped dense carbon layer improve charge separation and shuttle that prolonged photo-Fenton like reaction. Moreover, the catalyst is highly stable, collectible, and recyclable up to 5 cycles with high MB degradation efficiency. This work provides a new insight into the synthesis of highly visible-light sensitized biochar-supported photocatalyst through NH 3 -ambiance pyrolysis of NPs-laden biomass. Graphical abstract The novel photocatalyst N–TiO 2 –Fe 3 O 4 -biochar possesses high visible-light sensitivity and shows rapid degradation of methylene blue through synergism of adsorption, photodegradation, and Fenton-like reaction. Unlabelled Image [ABSTRACT FROM AUTHOR]

Highlights • Optimal biochar (∼39%) and bio-oil (∼19%) yields were obtained at 500 °C. • Basic functional groups on biochar surface were increased with higher temperature. • Acidic and carboxyl groups drastically reduce in biochar at HHT (700 °C). • Biochar produced at high temperature with fine particle size has higher stability. • Cost-benefit analysis showed the economic viability of biochar saleable system for all scenarios. Abstract In this study, the slow pyrolysis of rice husk was conducted by using a split-tube furnace under a nitrogen environment to investigate the influence of various pyrolysis conditions and biomass particle sizes on products yield distribution as well as physicochemical characteristics and surface chemistry of produced biochars. Results revealed that temperature has a more pronounced influence on products yield compared to the other operational conditions. The biochar yield decreases from 57.13 ± 5.37% to 37.19 ± 2.05% and gaseous phase yield increase from 25.64 ± 0.93% to 42.50 ± 4.58% with temperature increase from 300 °C to 700 °C. The surface chemistry of produced biochar varies widely as the distribution of different functional groups on its surface influenced by operational conditions and biomass particle size; above 500 °C the intensity of FTIR vibrational peaks reduces abruptly. FTIR, SEM, elemental composition and surface area results indicate that biochar synthesized under higher pyrolysis temperature, extended retention time and, lower heating and gas flow rates with fine biomass particle size has utility as a potential C-sequestration and remedial agent to mitigate global climate change and adsorption of environmental pollutants, respectively. Furthermore, biochar has potential application as a renewable solid bio-fuel source due to higher calorific values. A cost-benefit analysis indicates that the viability of biochar saleable product system is more economical with an annual profit of 138,533$ for the low scenario, when the presumed unit processes 2500 tons y−1 of biomass. In a comparison to other presumed scenarios, this system is more feasible in areas where low-cost RH biomass waste is available abundantly such as in rice production and processing areas. The profitability of this system increases further by accounting pyrolysis-gas energy value that reduces operational cost. For the optimization of biochar economical yield with desired properties, this work provides insight knowledge. [ABSTRACT FROM AUTHOR]