Amine-Modified Small Pore Mesoporous Silica as Potential Adsorbent for Zn Removal from Plating Wastewater

Abstract

The removal of Zn from wastewater generated from the Zn-based electroplating manufacturing process is essential because the regulation limit of Zn concentration in wastewater is becoming stricter in Japan. However, achieving this through conventional methods is difficult, especially for small and medium enterprises in the plating industry. Therefore, a suitable Zn-removal method with a low cost but high performance and Zn selectivity is required. The application of adsorbents is one possible solution. Mesoporous silica (MS) is a well-known adsorbent with controllable pore size, high specific surface area (SSA), high acid resistance, and ease of surface modification. In this study, we modified the surfaces of MSs with different initial pore sizes by amino groups and investigated their Zn removal performances. The effect of pore size on amine modification using (3-aminopropyl)triethoxysilane and on adsorption performance in a single system was investigated along with Zn adsorption selectivity in the Zn–Ni binary system. Amine-modified MS prepared from MS with an initial pore size of 1.9 nm showed drastically lower performance compared to those prepared from MS with an initial pore size larger than 2.8 nm. Zn-selectivity in the Zn–Ni binary system, containing equal amounts of Zn and Ni, was found to reach a maximum of 21.6 when modifying MS with an initial pore size of 2.8 nm.

Adsorption and desorption behavior of Zn2+ in a flow-through electrosorption reactor

“…Taking the 60 min at which the time of the adsorption process begins to decrease toward the difference as the assumed endpoint of adsorption, most of the adsorption process is completed within 20 min of the beginning of adsorption, and this trend increases as the pole-plate spacing approaches 3 mm. 8 , 17 , 22 The adsorption behavior starts with more adsorption sites on the surface of the activated carbon fiber mat, and the adsorption moves faster toward the equilibrium, as the adsorption process goes on, the number of sites on the surface of the activated carbon fiber mat gradually decreases and finally approaches the equilibrium, and the adsorption capacity no longer changes significantly. The comparison between the different electrode spacing groups demonstrated that the 3 mm electrode spacing had a significant advantage in relative adsorption of 23.14 mg/g and differed significantly from the other spacing configurations.…”