Mechanism on Cr(VI) removal from aqueous solution by camphor branch biochar.

Removal of Cr(VI) from aqueous solution by biochar obtained from landscaping waste of camphor branch was investigated in order to find new material in producing carbon-based sorbent. Cr(VI) removal efficiency experiments revealed that the optimum pyrolysis temperature of camphor branch was 350 °C (CBB350) and an initial solution pH at 2.0 was favorable for Cr(VI) removal. The characteristics and mechanism of CBB350 on Cr(VI) removal were studied via Brunauer - Emmett - Teller nitrogen adsorption method, the scanning electron microscope equipped with energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectrometer and kinetic analysis. The results suggested that Elovich equation was best fitted the complex reaction process with fitting correlation coefficient above 0.94, which prompted that the chemical reaction was the control step, the concentration of Cr(VI) decreased sharply at the beginning of the reaction and the removal rate was accelerated in high temperature. The removal mechanism was supposed that the vast bulk of Cr(VI) was reduced to Cr (III) through electrostatic interaction or form new stable inorganic ions and hexa-coordinate complexes chemically adsorbed on the surface of camphor branch biochar, a fraction of Cr(VI) was reduced to Cr (III) species retained or discharged in the solution and the rest Cr(VI) was directly adsorbed on the adsorbent.

Biochar regulates bacterial-fungal diversity and associated enzymatic activity during sheep manure composting.

Aimed to evaluate the coexistence of bacterial and fungal diversity and their correlation with enzymatic activity in response to biochar. This study performed aerobic composting based on typical agricultural wastes of sheep manure with additive apple tree branch biochar at distinct concentration (0, 2.5, 5, 7.5, 10 and 12.5% corresponding from T1 to T6). The result demonstrated that appropriate amendment of biochar enriched bacterial diversity (1646-1686 OTUs) but interestingly decreased fungal diversity (542-630 OTUs) compared to control (1444 and 682 OTUs). Biochar addition enhanced all enzymatic activities and its correlation with bacterial was more complex than fungal community (786 and 359 connect edges). The dominant microbes comprised of Firmicutes (45.2-35.2%), Proteobacteria (14.0-17.5%), Basidiomycota (32.4-49.5%) and Ascomycota (11.3-37.5%) among all the treatments. Overall, biochar regulates the composting microenvironment by influencing the microbial diversity and associated enzymatic activities.

Pollution control in biochar-driven clean composting: Emphasize on heavy metal passivation and gaseous emissions mitigation.

Present study was focus on the pollution control aspect of gaseous mitigation and heavy metal passivation as well as their associated bacterial communities driven by apple tree branch biochar (BB) during sheep manure composting. Six treatment was performed with distinct concentration of BB from 0%, 2.5%, 5%, 7.5%, 10%, and 12.5% as T1 to T6. Compared with compost without additive, biochar-based composting recorded faster thermophilic process (4thd) and longer duration (12-14d), lower gaseous emission in terms of ammonia (5.37-10.29 g), nitrous oxide (0.12-0.47 g) and methane (4.38-30.29 g). Notably highest temperature (65.3 â„ƒ) and active thermophilic duration (14d), minimized gaseous volatilization were detected in 10%BB composting. Aspect of non-degradability and enrichment-concentration properties of heavy metals, the total copper (Cu) and zinc (Zn) were increased (from initial 12.71-17.91 to final 16.36-29.36 mg/kg and 107.39-146.58-161.48-211.91 mg/kg). In view of available diethylene triamine pentacetic acid (DTPA) extractable form, DTPA-Cu and DTPA-Zn from 4.29 to 6.57 and 31.66-39.32 mg/kg decreased to 3.75-4.82 and 23.43-40.54 mg/kg, especially the maximized passivation rate of 46.95% and 56.27% were present in 10%BB composting. Additionally, bacterial diversity of biochar-based composting was increased (1817-2310 OTUs) than control (1686 OTUs) and dominant by Firmicutes (52.75%), Bacteroidetes (28.41%) and Actinobacteriota (13.98%). Validated 10% biochar-based composting is the optimal option for effectively control environmental pollution to obtain hygienic composting.

Surface properties and suspension stability of low-temperature pyrolyzed biochar nanoparticles: Effects of solution chemistry and feedstock sources.

Intensive application of biochar requires better understanding of their environmental behaviors such as stability, fate, and mobility. The release of bulk biochar into biochar nanoparticles (NPs) may bring risks because of their potential flowing into downstream water bodies with nutrients/containments attached. Low-temperature pyrolyzed biochars, namely fruit tree branch biochar of 350/450/550 °C (FB350, FB450 and FB550), corn straw biochar of 350 °C (CB350) and peanut straw biochar of 350 °C (PB350), were produced, and their NPs were extracted. The yield, elemental composition, mineral composition, surface functional groups and zeta potential of biochar NPs were characterized. Subsequently their suspension stability was evaluated in NaCl and CaCl2 solutions by dynamic light scattering technique. The Hamaker constants and particle interaction energy of the biochar NPs were calculated by adopting Derjaguin-Landau-Verwey-Overbeek theory. For biochar NPs of same feedstock, the stability of FB350/450/550-NPs could be predicted well by their zeta potential values. The types of their surface functional groups were the same while their adsorption intensity differed. The scenarios for biochar NPs of different feedstock sources were different, that is, inconsistent variation was observed between their zeta potential and suspension stability, which were rooted in the variable type and quantity of surface functional groups. In conclusion, feedstock was the most significant factor that influenced the suspension stability of biochar NPs, followed by the pyrolysis temperature and solution chemistry, which were highly dependent on surface potential. The findings provide references for the environmental risk evaluation of biochar NPs and reasonable application of biochar in field.