Abstract
Heavy metals contamination in bodies of water near mining sites is still prevalent. However, the challenge is monitoring contaminants in hard-to-reach areas, which can only be addressed using on-site and pretreatment-free detection of heavy metals. Herein, a simple Hg and Pb detection membrane was prepared using d-limonene and sulfur as by-products of orange zest and petroleum refining, respectively. The detection membrane included sulfur, which aids in the stabilization of limonene's ability to detect Hg and Pb. The coulometric system was used in the detection process. It was prepared by synthesizing limonene (from orange peelings) and integrating it in polysulfide. The as-prepared limonene polysulfide (LPS) was then coated into a membrane solid support. An LPS-polyvinyl alcohol (PVA) membrane was prepared via phase inversion technique. LPS typically have a dark red color, hence the coated PVA membrane adapted such color. The LPS-PVA membrane was exposed to an aqueous mercury solution, a bright yellow deposit formed on the polysulfide, which remains immobilized. Depending on the mercury concentration, the intensity of the color shift varied. A brighter color change was for Pb detection if the solution was alkaline. Hence, the results showed that waste orange peelings could be upcycled in an easy and simple Hg and Pb metals detection process, an intelligent waste management approach.
