Remediation of efavirenz using a magnetic molecularly imprinted titania nanocomposite

Abstract

In the current study, remediation of efavirenz as a model antiretroviral drug in wastewater effluents was investigated using a hybrid photodegrader based on titania embed on a magnetic molecularly imprinted polymer (MMIP). Initially, a MMIP was synthesized to specifically recognize and remove efavirenz from wastewater effluents. The magnetic smart polymer was synthesized via a bulk polymerization technique with efavirenz as the template, and p-vinyl benzoic acid the functional monomer in the presence of magnetite nanoparticles. The MMIP was characterized using Fourier transform infrared spectroscopy and thermogravimetric analysis. The performance of MMIP was optimized using a central composite design. The optimum conditions for effective adsorption of efavirenz were pH 6.5, MMIP mass of 15 mg, 1 mg L-1 efavirenz concentration and contact time of 40 min. The optimal binding capacity achieved after 40 min of contact time and neutral conditions was 44.9 µg g-1 . Batch studies revealed that pseudo-second order and the Langmuir isotherm were the models that explained the kinetics and mechanism of adsorption of efavirenz onto the MMIP. This suggested that the interaction between the MMIP and the efavirenz was through chemisorption and that once efavirenz binding reaches a maximum limit, no more binding occurs. The MMIP was finally applied in the removal of efavirenz from real wastewater effluents polluted with 3.99 ng mL-1 of efavirenz. The polymeric sorbent could achieve 44.8% removal efficiencies. Reusability studies showed less than 4% average loss in the binding capacity with every reuse cycle, while there was no loss in binding capabilities when the polymer was utilized at about half its binding capacity. Finally, photocatalytic degradation of efavirenz was investigated as a potential remedial tool for efavirenz in wastewater effluents. Titania was imbedded onto the MMIP to form a hybrid MMIP/TiO2 nanocomposite with the ability to trap efavirenz from wastewater followed by its vii photodegradation. Its performance was also investigated using factorial design involving initial concentration of efavirenz (20 - 60 µg L-1 ), mass of the MMIP/TiO2 (5 -15 mg) and the time of irradiation (20 - 40 min). The results were also observed in a form of contour plots. Up to 99% photodegradation of efavirenz was achieved within 15 min. However, it was observed that the photodegrader performed better under higher concentrations of efavirenz concentrations. In general, the synthesis and optimization of a hybrid molecularly imprinted titania nanocomposite for photodegradation of efavirenz in wastewater effluents was successful. Its performance has proven that it can be a viable tool for remediation of efavirenz in wastewater effluents. Efavirenz cannot be removed by conventional wastewater treatment processes and advanced technologies such as the MMIP/TiO2 nanocomposite synthesized in the current study could help minimize the release of efavirenz into surface water systems. This work has yielded three manuscripts; a review article and two research papers. The review has been published, one manuscript is under review and the final one has been drafted.