Nanoparticles of (calcium/aluminum/CTAB) layered double hydroxide immobilization onto iron slag for removing of cadmium ions from aqueous environment

Abstract

The novel point of this study represents by manufacturing new material for treating of aqueous solution laden with cadmium ions. This can achieve through utilizing of alum as cheapest and available substance, plaster kiln dust wastes from gypsum industry, and cetyl trimethyl ammonium bromide surfactant in the preparation of nano-sized layered double hydroxide of aluminum and calcium in the existence of mentioned surfactant. The gel-solution of nanoparticles can be co-precipitated on the iron slag to obtain new sorbent identified “iron-slag coated with (calcium/aluminum- cetyl trimethyl ammonium bromide) layered double hydroxide” and composition of all materials was characterized by analysis of X-ray diffraction. The outcomes proved that the area of slag surfaces was increased significantly from 0.49 to 10.21 m2/g due to the surfactant intercalation and precipitation of nanoparticles. The synthesis parameters require surfactant 0.035 g/50 mL, pH 10, molar ratio of (calcium/aluminum) 2, and mass of slag 1 g/50 mL. Batch tests proved that more than 99.3% cadmium can remove at time 60 min, initial pH 7, coated slag mass 0.5 g/50 mL, and speed 250 rpm for 50 mg/L initial concentration to obtain highest capacity of sorption of 14.50 mg/g. The measurements of kinetic tests were well followed the model of Pseudo second-order and; accordingly, the chemisorption mechanism will predominate the removal process. Model of intra-particle diffusion demonstrate that the electrostatic attraction, hydrogen bonding and diffusion are major mechanisms required in the cadmium removal onto the prepared sorbent. Also, Langmuir model is an ideal formula for representing the sorption data with determination coefficient = 0.99. Characterization tests certified that the nanoparticles on the slag can play a prime role in the enhancement of cadmium sorption. In addition, the exhausted sorbent can be regenerated and its efficiency was not less than 83% for removal of cadmium after 9 regeneration cycles.