Enhanced competitive adsorption of zinc and manganese by alginate-iron oxide-combusted coal gangue composite: Synthesizing, characterization and investigation

Reusing different mine gangue is an effective method to reduce environmental hazards around the processing plants. In this study, coal gangue (CG) of Anjirtangeh coal washing plant with high levels of Loss on ignition (LOI) are first combusted, then modified by iron oxide and alginate, and used as the adsorbent of zinc and manganese. The structure of the fabricated adsorbent was identified through XRD, XRF, FTIR, SEM and BET analyses. Among these analyses, BET shows that the surface area (3 m2/g) and the pores diameter (32 nm) of the adsorbent are not high. Hence, the functional groups play an influential role in the adsorption capacity. Further, the Cuckoo Optimization Algorithm was used to investigate the optimal conditions of the adsorption process and the results were investigated. The adsorption capacity of zinc and manganese in the optimal conditions was 115.6 and 101.8 mg/g, respectively, which reduced to 105 and 92.4 mg/g in competitive conditions, respectively. Isotherm studies of adsorption by different models showed that adsorption of zinc and manganese onto the alginate-iron oxide-combusted coal gangue (AICCG) composite was done chemically and desirably. Besides, the adsorption of zinc and manganese onto the fabricated composite was carried out in a heterogeneous process. Kinetic studies conducted by the use of reaction and diffusion-based models showed that the intra-particle diffusion model controls the adsorption process for both ions. Thermodynamic studies showed that the adsorption process of zinc and manganese onto the AICCG composite was spontaneous and endothermic. [Display omitted] •The introduction of novel composite, called alginate-combusted coal gangue composite.•Adsorbent characteristics determine the detailed structure of the new composite.•The surface area of novel composite was low; therefore, the functional groups played a significant role in the absorption process.•Competitive removal of zinc and manganese by alginate-combusted coal gangue composite.