Poly (amidoxime) modified magnetic activated carbon for chromium and thallium adsorption: Statistical analysis and regeneration

The study discusses the use of magnetic activated carbon modified with poly (amidoxime) (PAMC) as an efficient approach for the adsorption of chromium and thallium. Activated carbon was synthesized from waste rubber tires, subsequently enhanced with magnetic properties, and modified with poly (amidoxime) providing more functional groups and thus improve the sorption efficiency. The morphological and structural properties of the prepared materials were investigated using different characterization techniques including SEM-EDX, BET, and FTIR. The adsorption evaluation was carried out in accordance with a factorial design to determine the optimum condition for the removal process. Factorial design analysis ensures the use of limited resources while also obtaining the optimum efficiency of the adsorption process. A half factorial design method was adopted in this study. The conditions varied include; pH, the initial concentration of adsorbent, shaker speed, contact time and adsorbent dosage. The material showed high efficacy within a wide pH range (3–11) even with a small dosage of 1 g/L. Interestingly, the material showed good efficiency for the uptake of the test toxic metal ions at low and high concentrations of 1 and 20 ppm with acceptable statistical values. Shaker speed of 200 rpm was the optimum. More than 97% of the chromium was removed using each of 1 and 5 g/L of the adsorbent. Analysis of variance showed a high correlation for the removal process with p-values < 0.003 for the removal of thallium. To demonstrate how the material can be used in process engineering design and practice, regeneration of PAMC and the fate of the adsorbates were evaluated. Tests were also conducted using real wastewater. With easy separation and high efficiency of removal for both chromium and thallium from water and good regeneration without showing a significant loss in adsorption capacity even after several cycles, the material demonstrated its exciting potential as an adsorbent for water treatment.