Remediation of pharmaceuticals from lagoon water using biochar from rice husk and coconut husk

Abstract

The pollution of water bodies by pharmaceutical wastes, particularly from antibiotics, poses a global threat by contributing to antibiotic resistance and toxicity to aquatic life, as traditional wastewater treatment plants fail to remove these contaminants. Therefore, the study explored the possibility of using biochar made from rice husk, coconut fibre and coconut shell in the remediation of eight PHAs (erythromycin, metronidazole, sulfamethoxazole, caffeine, acetaminophen, aspirin, trimethoprim and ciprofloxacin) from lagoon water as most lagoons in Ghana serve as dumping sites for wastewater. The SEM and FTIR analysis revealed the porosity of biochars which were within the micro-meter range and CO, O-H, C=O as functional groups found on their surfaces respectively Additionally rice husk biochars contain Si-O-Si. Pharmaceuticals were extracted from water samples using C18 SPE cartridges and analysed using HPLC Shimadzu prominence UFLC 20AD coupled with UV-vis SPD-20AV to determine their levels. After conducting competitive batch adsorption tests on the eight pharmaceuticals, five biochars (CF53, CF61, RH53, RH61, and RH63) were selected based on their mean removal efficiencies (above 75 %). The adsorption kinetics (pseudo first and second order intraparticle diffusion), isotherm (Langmuir, Freundlich and Temkin) and thermodynamics were studied. The adsorption kinetics fitted the pseudo-second-order, and also occurred on both surface and in the pores according to the intraparticle diffusion model. The adsorption of the PHAs did not fit one isotherm suggesting that the adsorption was driven by mixed mechanisms involving both chemical and physical reactions and again the adsorptions were all favourable. The calculated values ΔH° and ΔG° indicated that the adsorption was exothermic and spontaneous. The selected biochars from coconut fibre and rice husk were effective in the removal of the different PHAs and can be used as an alternative to costly adsorbents for the removal of the eight PHAs from water.