Characteristics of phosphate biosorption on nanoparticles of different woody-sawdust used for controlling P runoff and a supplemental P-fertilizer

Abstract

To evaluate the potential of different woody sawdust nanoparticles (nSD) for phosphate biosorption capacity, a batch biosorption experiment was conducted on three types of sawdust nanoparticles. To achieve the objective, nanoparticles of the three types of woody-sawdust were produced by up-down method (ball mill mortar grinder) and phosphate solutions with various concentrations (5–320 mg/L), pHs, and temperatures were performed. The results revealed that the PO4 sorption capacity of sawdust nanoparticle of Kafour tree (nSD-KF) was much higher than that of guava (nSD-GU) and Gohanamia (nSD-GH). The Langmuir model was the best fit to the experimental sorption data. The maximum adsorption capacity (qmax) value of nSD-KF (50,000 μg/g) for phosphate was higher than those of nSD-GU (33,300 μg/g) and nSD-GH (18,200 μg/g) sorbents, respectively. The first-order equation has been proved to be one of the best studied kinetic equations that capable of describing the sorption kinetics and sorption rate of phosphate onto the studied biosorbents. The solution pH greatly affected the charges of the active sites of nSD-KF and influenced the phosphate behavior in the solution. The phosphate sorption increased on the studied biosorbent with the increase of reaction temperature from 298 to 318 K, with constant of all other reaction conditions. The highest efficiency of phosphate removal by nSD-KF was at temperature of 318K at pHs normal and 7. The results of this study revealed that the ion exchange process, high specific surface area of nSD-KF, and ion complexation between phosphate and sawdust nanoparticles may be occurred in phosphate biosorption. The Fourier transform infrared analysis confirmed ion complexation between phosphate and sawdust nanoparticles depending on the chemical constituents of sawdust that containing many functional groups such as carboxylic, phenolic, hydroxyl, and carbonyl groups. In conclusion, the application of nanoscale sawdust particles in wastewater or wastewater-irrigated soils would substantially decrease P runoff and eutrophication. Moreover, the P-enriched nSD-KF may be used as a supplemental P-fertilizer required for plant growth to overcome high cost of mineral fertilizers applied to the agricultural soils.