Novel design of microsphere adsorbent for efficient heavy metals adsorption

Abstract The fabrication of high‐efficiency and low‐cost adsorbent for the wastewater treatment is a challenging task. In this study, a hollow sphere adsorbent was synthesized from solid waste coal gangue through a facile spray drying method and subsequent calcination. The structure of the synthesized coal gangue microsphere (CM) have been characterized by multimethods including X‐ray diffraction, scanning electron microscope, Fourier transform infrared, and others. The factors influencing the adsorption for Cu ²⁺ and Pb ²⁺ by CM were also investigated systemically; pH between 6 and 8 was found to be optimal for Cu ²⁺ and Pb ²⁺ adsorption. The isotherm and kinetic analysis reveal that the adsorption process could be well represented by Langmuir and pseudo–second‐order model with a higher R ² and low χ ² value. According to Langmuir model, the maximum adsorption capacity was calculated to be 6.570 and 18.904 mg/g for Cu ²⁺ and Pb ²⁺ at 25°C, respectively. The adsorption mechanism was proposed to contain not only the surface reaction process, but also the diffusion process. Consequently, the economic and environmental benefits make CM a promising adsorbent in wastewater treatment.