Green synthesis of ZnO coated hybrid biochar for the synchronous removal of ciprofloxacin and tetracycline in wastewater

Preparation of biochar from kaolinite and coconut husk (KCB) and further activated with HCl (KCB-A) and KOH (KCB-B) via a microwave technique for the remediation of ciprofloxacin (CIP) and tetracycline (TET) from water was carried out. Characterization using scanning electron microscopy, energy dispersive X-ray, Fourier transform infrared spectroscopy and X-ray diffraction showed the successful synthesis of functionalized biochars. Batch adsorption experiments demonstrated the potential of the adsorbents for fast and efficient removal of CIP and TET from solution. The adsorption capacities were found to be 71, 140 and 229 mg g(−1) for CIP and 118, 117 and 232 mg g(−1) for TET removal on KCB, KCB-A and KCB-B, respectively. For KCB, KCB-B and KCB-B, CIP adsorption best followed the pseudo second order kinetic model (PSOM), pseudo first order kinetic model (PFOM) and intraparticle diffusion (IDP) respectively. TET adsorption followed PSOM for KCB, IPD for KCB-B and PFOM for KCB-A. CIP adsorption on KCB, KCB-A and KCB-B best fit the Temkin, Langmuir and Brouers–Sotolongo isotherms, respectively, and TET adsorption on KCB best fit Brouers–Sotolongo while KCB-A and KCB-B best fit Langmuir–Freundlich. Adsorption of both contaminants was thermodynamically feasible showing that these materials are excellent adsorbents for the treatment of pharmaceuticals in water.