Sustainability assessment of acid-modified biochar as adsorbent for the removal of pharmaceuticals and personal care products from secondary treated wastewater

Abstract

This study investigated the adsorption behavior and sustainability of biochar to remove four pharmaceutical and personal care products (PPCPs). The biochar (PEBC) was prepared via slow pyrolysis of empty palm bunch (PEB) at three temperatures (250–750 °C). To improve the adsorption capacity further, PEBC450 was acid treated with H2SO4 to develop PEBC450-A. The adsorption behavior of target pollutants (methyl paraben (MPB), carbamazepine (CZP), ibuprofen (IBP), and triclosan (TCS)) onto PEBC450-A was studied in batch experiments, and phenomenological and statistical models were applied to understand the sorption mechanism. Results demonstrated that the adsorption system was able to achieve fast equilibrium (in 4 h), with maximum adsorption capacities as 60.2 mg/g (MPB), 51.7 mg/g (CZP), 38.8 mg/g (IBP), 35.4 mg/g (TCS). The modeling results showed heterogeneous adsorption of PPCPs involving the participation of multiple functional groups in parallel and non-parallel orientations. The mass transfer kinetic models identified the internal mass transfer resistance as the rate-limiting step. The PPCPs adsorption was significantly affected by the change in solution pH and the presence of humic acid. However, no substantial change in PPCPs removal was observed in the presence of co-existing ions and different ionic strengths. In multi-pollutant systems and real water samples, PEBC450-A maintained more than 75% removal of target pollutants, indicating the developed material as a promising adsorbent for wastewater treatment. The sorption mechanism was found to be channel diffusion, hydrogen bonding, n-π and π-π interactions, and van der Waals force. The comparative life cycle assessment of PEBC450-A and commercial activated carbon showed that the total impact contribution of PEBC450-A was 20 times less than commercial activated carbon. The overall finding makes PEBC450-A a low-cost and sustainable adsorbent for water treatment.