Polyamide magnetic palygorskite for the simultaneous removal of Hg(II) and methyl mercury; with factorial design analysis.

A novel efficient adsorbent was prepared by the modification of magnetic palygorskite (MPG) by polyamide via the interfacial polymerization of trimesoyl chloride with m-phenylenediamine. The prepared magnetic palygorskite modified with polyamide (MPGP) material was appraised for its removal of the Hg(II) and CH3Hg species from aqueous solutions. The developed adsorbent was characterized using spectroscopic techniques. The adsorption ability of the MPGP sorbent was systematically investigated by using the batch method. Factorial design analysis was applied to study the effect of different batch parameters on the adsorption yield of both mercury species. These factors include mercury concentration, initial pH, sorbent amount and contact time. The equilibrium data coincided with the Langmuir adsorption isotherm indicating the maximum adsorption capacity of the MPGP was determined as 211.93 mg/g for Hg(II) and 159.73 mg/g for CH3Hg. The kinetic mechanism of the adsorption of both mercury species was well defined by the pseudo-second-order while the adsorption processes demonstrated spontaneity and an exothermic character at the studied temperatures. The cycling adsorption/desorption tests made by using a 1 mol/L HCl solution demonstrated that the MPGP had good reusable performance up to seven cycles. Based on the results it can be suggested that the synthesized MPGP sorbent can be handled for the elimination of Hg(II) and CH3Hg from wastewater effluents.