Adsorption of Cu(II) on silica gel synthesized from chemical bottle glass waste: Response surface methodology-Box Behnken design optimization

Abstract

Recent research has reported on the extraction and synthesis of silica gels from a waste glass of chemicals. This study aims to optimize silica gel synthesized from chemical glass waste as heavy metal adsorbent Cu2+. Silica gel adsorbent has been successfully synthesized by reacting silica from chemical glass waste and sodium hydroxide (NaOH) by a fusion reaction and sol–gel process. Synthesized silica gel has an amorphous diffractogram at 2θ 20–30°, a purity of 75.63 %, a surface area of 297.08 m2/g, and a pore radius of 15.74 nm. The adsorption formulation was optimized using Design Box–Behnken and optimum conditions were obtained at adsorbent doses close to 3.5 g, initial concentration 50–100 ppm, contact time 10 min, and pH 9. Adsorption Isotherm Langmuir, Freundlich, Temkin, and Dubinin–Raduskevich were investigated to determine the mechanism of adsorption. Adsorption data show that the adsorption is well-fitted to the Langmuir isotherm model. The results of SEM–EDX characterization showed that the surface morphology of silica gel showed a spherical and irregular surface then after adsorption cu metal was distributed on the surface of the silica gel. Based on all the results of the study it can be indicated that silica gel synthesized from chemical glass bottle waste can be applied as adsorbent Cu2+.