Coeffect of pyrolysis temperature and potassium phosphate impregnation on characteristics, stability, and adsorption mechanism of phosphorus-enriched biochar.

Potassium phosphate (K3PO4)-impregnated bamboo was pyrolyzed at temperatures ranging from 350 to 950 °C to explore the coeffect of pyrolysis temperature and K3PO4 impregnation on biochar's characteristics and adsorption behavior. The degree of aromatization and graphitization in phosphorus-enriched biochars (PRBCs) rose as temperature increased, whereas H/C and O/C ratios, pH value, and O-containing group content decreased. The pre-aging impact of K3PO4 impregnation results in increased stability and adsorption performance of PRBCs. Adsorption mechanism of PRBCs to heavy metal varies from pyrolysis temperature. Micropores dominate medium-temperature PRBCs (prepared at 550 âˆ¼ 750 °C), possessing the highest P-containing group content (116 % that of PRBC-350) and maximal adsorption capacity (greater than289 mg/g). The medium-temperature PRBCs adsorb Cd (II) via the role of O-containing groups, PO43-, and P2O74-, mainly by reactions of organic complexation, precipitation and inorganic complexation, respectively. 550 °C is the optimal pyrolysis temperature for both energy saving and heavy metal adsorption.

Effects of phosphorous precursors and speciation on reducing bioavailability of heavy metal in paddy soil by engineered biochars.

Ammonium phosphate (AP), phosphoric acid (PC), and potassium phosphate (TKP) were used for the modification of biochar for enhanced heavy metal passivation in soil. The effect of various phosphorus (P) precursors on adsorption-related properties, P speciation distribution pattern, and the passivation mechanism was investigated by BET, FTIR, XRD, XPS, and 31P NMR analysis. The mobility and bio-availability of cadmium (Cd) were studied by extraction experiments, and the P release kinetics was also determined. Results showed that the immobilization efficiency of Cd (II) by biochars followed the order: TKP-BC > PC-BC > AP-BC > BC, and TKP-BC reduced available Cd content by 81% treated with 2% addition. The P speciation shows a significant effect on the P-enriched biochars' passivation performance, especially orthophosphate, which is essential for the immobilization of Cd2+ by forming phosphate precipitation. Pyrophosphate and orthophosphate monoester in AP-BC and PC-BC can promote Cd2+ passivation via the formation of P-Cd complexes or organometallic chelates. It is also shown that PC-BC has the lowest P release rate while TKP-BC has the highest percentage of P (15.50%) remaining in the biochar. The results may contribute to the development of modified biochar for soil remediation based on P-related technologies.

Effect of phosphorus-modified biochars on immobilization of Cu (II), Cd (II), and As (V) in paddy soil.

Novel phosphorus-modified biochars were produced by pyrolyzing biomass feedstocks (wood, bamboo, cornstalk and rice husk) pre-impregnated with potassium phosphate (K3PO4). The soil heavy metal immobilization performance and mechanisms of modified biochars were investigated. Incubation experiments showed that impregnation with phosphorous can decrease the extraction of Cu (II) and Cd (II) by 2 to 3 times. Phosphorus-modified biochars enhanced the transformation of Cu (II) and Cd (II) ions from acid soluble to more stable forms. Characterization results showed that phosphorus (P) compounds in modified biochar played a vital role to immobilize Cu (II) and Cd (II) by forming precipitates or complexes with them. Additionally, the modified rice husk and cornstalk biochars have in the average 14-24% and 19-33% higher immobilization efficiency for Cd (II) and Cu (II) than the other two P-assisted biochars. However, regardless of the feedstock, both the extraction and mobility of As (V) were increased by phosphorous. This study indicates that the P-modified biochar can serve as a novel remediation agent for heavy metal polluted soils.

Effects of biomass pyrolysis derived wood vinegar on microbial activity and communities of activated sludge.

The effects of wood vinegar (WVG) on microbial activity and communities of activated sludge were investigated in a sequencing batch reactor (SBR) process. Results showed that the optimal WVG concentration was 4 µL/L when the pollutants removal efficiency and microbial activity were promoted by a WVG dilution factor of 1000. WVG could reduce the increase in microbial species richness, which led to a more notable variety of microbial species diversity. The enhanced microbial activity and communities were addressed to the promotion of 7 main classes of microbes in Proteobacteria, Bacteroidetes, Acidobacteria, and Nitrospirae phyla. The growth of ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), and main genera of denitrifying bacteria (DNB), phosphorus-accumulating organisms (PAOs), and glycogen-accumulating organisms (GAOs) could be promoted by WVG, which improved the sewage treatment effectiveness in a SBR.