Adsorption of nitrate and phosphate ions using ZnCl2-activated biochars from phytoremediation biomasses

Abstract

Mishandling and disposal of post-harvested phytoremediation biomass results in secondary pollution. Biochar production is one of the available technologies for processing post-harvested phytoremediation biomasses. The main objective of this study was to assess the potential adsorption of PO43- and NO3- ions from a binary solution by ZnCl2-activated phytoremediation biochars. The biochars were activated using ZnCl2 and analyzed for specific surface area, pore size, volume, surface morphology, point of zero charges (pHpzc), surface functional groups, and elemental composition. Subsequently, the adsorption potential for PO43- and NO3- ions of the activated biochar was investigated. Activation of phytoremediation biochars led to the development of new micropores and increased specific surface area range from 1.62-4.72 m2 g-1 to 4.75- 55.50 m2 g-1. ZnCl2 activation reduced the pHpzc values of Cymbopogon citratus, Cymbopogon nardus, and Chrysopogon zizanioides biochars (BCL2, BCC2, and BCV2) from 9.75, 9.50, 9.62 to 5.72, 5.51, and 6.23, respectively. Activated Chrysopogon zizanioides biochar (ACBCV2), activated Cymbopogon nardus biochar (ACBCC2) and activated Cymbopogon citratus biochar (ACBCL2) showed maximum potential phosphate ion adsorption capacities of 115.70, 101.74, and 270.59 mg g-1, respectively. ACBCL2, ACBCC2, and ACBCV2 indicated maximum potential nitrate ion adsorption capacities of 155.78, 99.42, and 117.71 mg g-1. BCC2, BCL2, ACBCV1, ACBCV2, and ACBCC2 best fitted the Langmuir linear form 1 model during NO3- adsorption. The results obtained in this study showed that ZnCl2-activated phytoremediation biochars have the potential to remove PO4 3- and NO3- ions from PO4 3- and NO3- ions binary solution.