Preparation of Porous CuS/modified-diatomite Composite Via a Facile in Situ Loading Process for Efficient Recovery of Silver Ion from Aqueous Solution

The study on the recovery of silver ion (Ag+) from silver-containing wastewater is of great significance to heavy metal pollution control and noble metal retrieval. In this work, a porous CuS/modified-diatomite composite was prepared via a pre-modification followed by a mild in situ coating process. A layer of CuS nanosheets was evenly coated onto pre-modified diatomite, and porosity of the diatomite support reserved. Aperture analysis results suggested that the composite possessed a broader porous distribution, higher specific surface area and pore volume than pure CuS. The neosynthetic composite exhibited outstanding adsorption performance for Ag+, according to the Langmuir adsorption isotherm model, with a maximum adsorption capacity of 822.7 mg/g for Ag+, approximately 84 times greater than that of raw diatomite (9.87 mg/g). The highest removal efficiency of the composite for Ag+ reached 99.9 %, and pH values (3-8) and coexisting ions (Na+, K+, Ca2+ and Mg2+) had little influence on the removal of Ag+. Kinetic studies and adsorption product analysis demonstrated that removal of Ag+ on the composite was occupied by chemisorption, arising from that the abundant porosity of diatomite support prompts Ag+ to diffuse onto the composite, and the uniformly coated CuS nanosheets provide abundant active sites for Ag+ chemisorption.