Highly efficient removal of the bisphenol A from aqueous solution by activated carbon derived from cores of nuts of Sapindus mukorossi

Endocrine-disrupting compounds (EDCs) are an important class of emerging contaminants detected in the aquatic environment. Among these compounds, bisphenol A (BPA), an EDC with a weak estrogen-like effect, has caused great concern because of its potential risk to human health. The main objective of this research was to study the efficiency of BPA removal from an aqueous solution using activated carbon (AC) synthesized from cores of nuts of Sapindus mukorossi (CNSM) by chemical activation. AC prepared via H3PO4 activation (CNSM-ACH) showed the highest removal efficiency of BPA compared to CNSM-AC activated by other chemicals. CNSM-ACH was characterized by proximate-ultimate analysis, iodine number, N-2 adsorption/desorption isotherms, scanning electron microscopy (SEM), FTIR spectroscopy, Boehm titration, and zeta potential. The results showed that CNSM-ACH has a high BET surface area and well-developed mesoporous structure. The adsorption experiments were carried out as a function of contact time, initial concentration of BPA, pH, ionic strength, adsorbent dose, and temperature. The kinetics data were fitted by three models, namely, the pseudo-first-order, pseudo-second-order, and intra-particle diffusion. The result revealed that the adsorption follows a pseudo-second-order kinetic. Furthermore, the isotherm models were evaluated using the nonlinear model fitting analysis based on the error functions. From the thermodynamic study, the adsorption was spontaneous and exothermic. Regeneration tests further confirmed that CNSM-ACH has promising potential in its reusability showing a removal efficiency of more than 80% even after five consecutive cycles. This study clearly shows that AC synthesized from cores of nuts of Sapindus mukorossi can be an alternative to the commercially available adsorbent for the removal of BPA from an aqueous solution.