Adsorption of cadmium(II) in wastewater by magnesium oxide modified biochar

A new MgO-AC (magnesium oxide modified activated carbon) adsorbent was successfully synthesized under microwave irradiation. XRD, FT-IR, XPS, SEM and N₂ adsorption were used to characterize the properties of MgO-AC. It was found that MgO-AC was highly crystalline under the preparation process, and the doping of MgO (Magnesium oxide) did not cause the gap blockage of AC (activated carbon), but the micropore area and average pore size of modified AC increased significantly. Multiple conditional parameters were studied to determine the optimal adsorption effect, such as roasting temperature, holding time, MgO doping amount, contact time, adsorption temperature, system pH, and initial concentration of Cd(II) (divalent cadmium ion). The results show that the optimal parameter conditions are as follows: the insulation temperature is 800 °C, holding time of 40 min, the doping amount of MgO is 1/20 of AC, and the maximum adsorption capacity is 649.9 mg·g^?1 at pH = 7. In addition, thermodynamic studies show that the adsorption process is spontaneous and endothermic, and kinetic and adsorption isotherm models show that the pseudo-second-order kinetic model and Langmuir model are well fitted for the adsorption process.