Cleavable porous silicon based hybrid material for pre-enrichment of trace heavy metal ions

The paper reports on the preparation of the cleavable porous silicon (PSi) based hybrid material and application in pre-enrichment of trace heavy metal ions. The cleavable groups (benzimidazoledithio) were grafted on the PSi surface by a stepwise covalent process. PSi was first obtained by anodization of bulk silicon wafers and was subsequently silanized by 3-mercaptopropyltriethoxysilane (MPTS) to synthesize MPTS-PSi, the MPTS-PSi was further converted into pyridyldithio-terminated PSi (PDT-PSi), and finally, the PDT-PSi reacted with 2-mercaptobenzimidazole to form the benzimidazoledithio modified PSi (BDT-PSi). Scanning electron microscopy (SEM) was used to characterize the morphology of freshly prepared and modified PSi. Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy were performed to confirm the effectiveness of each step graft. According to the UV–vis spectra analysis, the disulfide linkage of BDT-PSi can be dissociated in presence of reduced glutathione (GSH). The pre-enrichment efficiency of BDT-PSi was investigated at the different pH for the different metal species (Cd, Hg, Pb, Cu and Co). The results show that the BDT-PSi possesses a similar preferential adsorption trend (Cd > Cu ≫ Hg ∼ Pb ∼ Co) at different pH (from 2.0 to 6.0). At pH 5.0, the best pre-enrichment efficiency for Cd ions is observed, the concentration of Cd is increased more than ten times and the recovery is found to be 95.4%.