Elucidating the mechanisms determining the availability of phosphate by application of biochars from different parent materials.

The consortium of minerals and organic matter notably alters and affects minerals' surface characteristics and nutrients providence. Organic matter such as biochar can modify the availability status of macronutrients like phosphorus (P). Despite some investigation, the adsorption/desorption of P with pure iron (hydr)oxides and the probable mechanisms involved are still unknown. In the present study, the goethite/hematite or goethite-biochar/hematite-biochar complexes were prepared, and a batch experiment with different P concentrations, time spell, pH, and ionic strength is performed to evaluate the sorption characteristics of P. The results of our study suggest that the P adsorption on mineral surface decreased with the increasing pH. Furthermore, the coexistence of biochar and minerals significantly inhibits P adsorption on the minerals surface. The results of Languimner and Freundlich's equations signify that the biochar-minerals complexes have heterogeneous adsorption sites and the presence of biochar reduces P adsorption on minerals surface. Among four biochars including peanut straw biochar (PC (B1)), rice straw biochar (RC (B2)), canola straw biochar (CC (B3)), and soybean straw biochar (SC (B4)), PC was more effective than other biochars to inhibit P adsorption on minerals surfaces.

Effect of different phosphorus sources on soybean growth and arsenic uptake under arsenic stress conditions in an acidic ultisol.

Soil arsenic (As) contamination is a serious concern because of its mark negative impacts on plant growth and physiological processes. In plant-soil system, As competes against phosphorus (P) which depends on charge component of different soil types. The main objective of this study was to investigate the influence of ((NH4)3PO4 (PO43-) and Ca5(PO4)3(OH) (phosphorite)) in ameliorating As stress on plant physiological process against As toxicity and their role in As accumulation. We performed eighteen treatments with different levels of As (0, 35, and 70 mg/kg) and P (0, 100, and 200 mg/kg) against two P sources of PO43- and phosphorite. Overall, more improvement in plant growth was observed by addition of PO43- than phosphorite. Significant increases in plant height (51%), dry biomass (root (49%) and shoot (40%)), chlorophyll contents (88%), total soluble sugars (58%) and plant functional leaves (51%) were observed by PO43- application as compared to their corresponding un-fertilized treatment under As stress conditions. However, proline and MDA contents were decreased by 49% and 71% with PO43- applied, respectively, under As stress. The As and P uptake by soybean were remarkably enhanced by the application of PO43- than phosphorite. Therefore, highly soluble P supplementation has great potential to minimize As-induced damage to plant growth in acidic soils and improve As uptake by plants. The findings obtained in present study will be used as an important tool for amelioration of As polluted acidic soils.

Arsenic and fluoride removal by potato peel and rice husk (PPRH) ash in aqueous environments.

Finding appropriate adsorbent may improve the quality of drinking water in those regions where arsenic (As) and fluoride (F-) are present in geological formations. In this study, we evaluated the efficiency of potato peel and rice husk ash (PPRH-ash)-derived adsorbent for the removal of As and F from contaminated water. Evaluation was done in batch adsorption experiments, and the effect of pH, initial adsorbate concentration, contact time, and adsorbent dose were studied. Characteristics of adsorbents were analyzed using scanning electron micropcope (SEM) and Fourier transform infrared (FTIR) spectroscopy. Both the Langmuir and Freundlich isotherm models fitted well for F- and As sorption process. The maximum adsorption capacity of adsorbent for As and F- was 2.17 µg g-1 and 2.91 mg g-1, respectively. The As and Fi removal was observed between pH 7 and 9. The sorption process was well explained with pseudo-second order kinetic model. Arsenic adsorption was not decreased in the presence of carbonate and sulfate. Results from this study demonstrated potential utility of this agricultural biowaste, which could be developed into a viable filtration technology for As and F- removal in As- and F-contaminated water streams.