Coupled sorptive and oxidative antimony(III) removal by iron-modified biochar: Mechanisms of electron-donating capacity and reactive Fe species.

Sorption and oxidation are two potential pathways for the decontamination of trivalent antimony (Sb(III))-bearing water, using iron (Fe)-modified biochar (FeBC). Here we investigated the sorption and oxidation behavior of FeBC for Sb(III) in aqueous solutions. Results revealed that Sb(III) removal by FeBC was significantly improved showing the maximum Sb(III) sorption (64.0 mg g-1). Density functional theory (DFT) calculations indicated that magnetite (Fe3O4) in FeBC offered a sorption energy of -0.22 eV, which is 5 times that of non-modified biochar. With the addition of peroxymonosulfate (PMS), the sorption of Sb(III) on FeBC was 7 times higher than that on BC, indicating the sorption capacity of FeBC for Sb(III) could be substantially increased by adding oxidizing agents. Electrochemical analysis showed that Fe modification imparted FeBC higher electron-donating capacity than that of BC (0.045 v. s. 0.023 mmol e- (g biochar)-1), which might be the reason for the strong Sb(III) oxidation (63.6%) on the surface of FeBC. This study provides new information that is key for the development of effective biochar-based composite materials for the removal of Sb(III) from drinking water and wastewater. The findings from this study have important implications for protecting human health and agriculture.

Chitin and crawfish shell biochar composite decreased heavy metal bioavailability and shifted rhizosphere bacterial community in an arsenic/lead co-contaminated soil.

Sustainable management of ever-increasing organic biowaste and arable soil contamination by potentially toxic elements are of concern from both environmental and agricultural perspectives. To tackle the waste issue of crawfish shells and simultaneously minimize the threat of arsenic (As) and lead (Pb) to human health, a pot trial was conducted using chitin (CT), crawfish shell biochar (CSB), crawfish shell powder (CSP), and CT-CSB composite to compare their remediation efficiencies in As/Pb co-contaminated soil. Results demonstrated that addition of all amendments decreased Pb bioavailability, with the greatest effect observed for the CT-CSB treatment. Application of CSP and CSB increased the soil available As concentration, while significant decreases were observed in the CT and CT-CSB treatments. Meanwhile, CT addition was the most effective in enhancing the soil enzyme activities including acid phosphatase, α-glucosidase, N-acetyl-ß-glucosaminidase, and cellobiohydrolase, whereas CSB-containing treatments suppressed the activities of most enzymes. The amendments altered the bacterial abundance and composition in soil. For instance, compared to the control, all treatments increased Chitinophagaceae abundance by 2.6-4.7%. The relative abundance of Comamonadaceae decreased by 1.6% in the CSB treatment, while 2.1% increase of Comamonadaceae was noted in the CT-CSB treatment. Redundancy and correlation analyses (at the family level) indicated that the changes in bacterial community structure were linked to bulk density, water content, and As/Pb availability of soils. Partial least squares path modeling further indicated that soil chemical property (i.e., pH, dissolved organic carbon, and cation exchange capacity) was the strongest predictor of As/Pb availability in soils following amendment application. Overall, CT-CSB could be a potentially effective amendment for simultaneously immobilizing As and Pb and restoring soil ecological functions in contaminated arable soils.

Phosphorus runoff from agricultural land and direct fertilizer effects: a review.

Phosphorus (P) is one of the most important mineral nutrients in agricultural systems, and along with nitrogen (N), is generally the most limiting nutrient for plant production. Farming systems have intensified greatly over time, and in recent years it has become apparent that the concomitant increase in losses of N and P from agricultural land is having a serious detrimental effect on water quality and the environment. The last two decades have seen a marked increase in research into the issues surrounding diffuse losses of P to surface and ground water. This paper reviews this research, examining the issue of P forms in runoff, and highlighting the exceptions to some generally held assumptions about land use and P transport. In particular the review focuses on P losses associated with recent P fertilizer application, as opposed to organic manures, both on the amounts and the forms of P in runoff water. The effects of the physicochemical characteristics of different forms of P fertilizer are explored, particularly in relation to water solubility. Various means of mitigating the risk of loss of P are discussed. It is argued that the influence of recent fertilizer applications is an under-researched area, yet may offer the most readily applicable opportunity to mitigate P losses by land users. This review highlights and discusses some options that have recently become available that may make a significant contribution to the task of sustainable management of nutrient losses from agriculture.