Selective capture of mercury(II) in aqueous media using nanoporous diatomite modified by allyl thiourea

We herein aim to construct a novel sorbent (DT-S) possessing adsorption selectivity to mercury(II) in aqueous media. Silanized purified diatomite (DT-N) was first synthesized by grafting 3-aminopropyltrimethoxysilane (APS) onto purified diatomite (DT). Nanoporous DT-S was then constructed through successively grafting epichlorohydrin (ECH) and allyl thiourea (AT) onto DT-N. FTIR, elemental analysis (EA), Brunauer–Emmett–Teller (BET), XRD, SEM, and pH at the zero point of charge (pH zpc ) results demonstrated that DT-S had ample –OH, –NH 2 , and C=S, specific surface area of 5.52 m 2 /g, small pore diameter (16.10 nm), porous structures, and pH zpc of 5.80, favorable for Hg(II) capture. Optimal adsorption parameters were determined through batch tests. Capture behavior was interpreted preferably by pseudo-second-order kinetic and Liu isothermal equations. DT-S’ capture features, e . g ., monolayer, spontaneity, chemisorption, and endothermic reaction, were evidenced by the data obtained. DT-S had 56.30 mg/g of maximum adsorption capacity for Hg(II), exceeded some sorbents available. Competitive adsorption tests displayed remarkably selective ability to capture Hg(II) (> 80.01%). FTIR and XRD analyses validated a possible capture mechanism, i . e ., chelation reactions took place between mercury ions and nitrogen, oxygen, or sulfur atom in solid–liquid interface. Altogether, DT-S with high removal efficiency, capture selectivity, and excellent reusability is expected to be new sorbent applied to Hg(II)-contaminated water purification. Graphical abstract