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ABSTRACT: Pharmaceutical compounds in surface waters are an emerging environmental concern due to their biological activity, which consequently present a new challenge for drinking water and wastewater treatment systems. In this work, diclofenac (DCF) and indomethacin (IDM) have been used as target molecules or templates in order to be removed by means of molecularly imprinted polymers (MIP). MIP-DCF and MIP-IDM were synthesised and tested using two mathematical models, which are Lagergren and Thomas models. In addition, functional groups of the active functional sites and the target molecules have also been studied by using Fourier transform infrared spectroscopy. Both MIPs followed the Lagergren pseudo first order kinetic model. Comparing the original MIP-DCF and MIP-DCF after loading with DCF, differences in their functional groups were found. In conclusion, MIP-DCF and MIP-IDM work as good sorbents to recover these emerging pharmaceuticals persistent pollutants from water.
Keywords: Molecularly imprinted polymer, MIP, diclofenac, indomethacin, diclofenac recovery
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1.INTRODUCTION
A few decades ago, emerging persistent pharmaceutical pollutants (EPPPs) have been introduced as one type of recalcitrant pollutant sources in water.1 Recent studies have demonstrated that, despite the relatively low concentrations of pharmaceuticals in the environment (typically in sub-parts-per-billion levels), pharmaceuticals are of great concern due to their potential long-term adverse effects on humans and wildlife.2
Nowadays, there are many methods used for the recovery of pharmaceuticals, such as photocatalysis and sorbents, but they present some drawbacks, e.g., after photocatalysis the by-product generated may be more harmful than the parent compounds.3 There are many kinds of sorbents that have been studied, but not all the sorbents have the potential to recover the target molecules. In this work, molecularly imprinted polymers (MIPs) as a separation method is proposed and characterised. The polymeric matrices obtained using the imprinting technology are robust molecular recognition elements able to mimic natural recognition entities.4 MIPs are also good sorbents because of their porosity and their robustness properties. In this study, the removal of diclofenac (DCF) and indomethacin (IDM) have been carried out using MIPs, synthetised via bulk polymerisation with allylthiourea (AT) as the functional monomer and using DCF or IDM as template (MIP-DCF or MIP-IDM, respectively). DCF and IDM were detected using spectrophotometry.
To study the properties of the sorbents, MIPs have been...