Chromium Removal Using a Basalt Rock Adsorbent in a Packed Bed Column for Efficient Environmental Protection

The discharge of chromium(VI) into the environment is becoming a significant global concern. Despite the existence of numerous techniques for chromium(VI) removal, substantial challenges persist in effectively mitigating this issue. Therefore, this study investigates the feasibility of using low-cost basalt rock as an adsorbent for chromium(VI) removal. The adsorbent was prepared through size reduction and activation and subsequently characterized by using X-ray diffraction and Fourier transform infrared procedures. The characterization revealed that the adsorbent predominantly consists of SiO₂ and Al₂O₃ and contains functional groups that facilitate the adsorption mechanism. The adsorption potential of the basalt rock was initially evaluated in a batch adsorption procedure, which yielded an adsorption capacity of 14 mg/g. The batch adsorption results were best fitted by the Langmuir adsorption isotherm, with an <i>R</i> ² > 0.9, indicating monolayer adsorption. Subsequently, continuous adsorption was conducted using a fixed-bed column to assess the influence of operational parameters and evaluate the desorption behavior of the adsorbent by using fixed-bed models. Breakthrough curves were utilized to assess the fixed bed performance, revealing that increased column depth and decreased flow rate extend the saturation time of the bed. The experimental data from the fixed-bed column fit the bed depth service time and Yoon-Nelson models well. The adsorbent demonstrated successful reuse across four consecutive cycles, with the regenerated basalt rock adsorbent exhibiting a chromium(VI) adsorption capacity of 2 mg/g in the fourth cycle, retaining approximately 23% of its initial adsorption capacity. The findings of this research indicate that the basalt rock-based adsorbent possesses significant potential for removing chromium(VI) from aqueous solutions in a continuous adsorption bed column.