The Effect of Modifying Coal Mining Waste on the Removal of Cadmium from Aqueous Solutions

The presence of excessive concentrations of metals like cadmium, chromium, cobalt, mercury, lead, zinc and arsenic, inside the human or animal body is very dangerous as they are non-biodegradable in nature and have long biological half-lives and can accumulate in different parts of the body. Therefore, the removal of these heavy metals from water and sewage sludge is an important problem. Adsorption process is considered as one of the most effective processes for the removal of heavy metals. Different materials are used as adsorbents. The choice of inexpensive and efficient adsorbent in the process of removing pollutants is the most important factor in the absorption method. In this study, capacity of the coal mining waste as natural and modified by NaOH for remove of cadmium contaminant element was investigated. Adsorption isotherms and kinetics were performed to calculate the capacity and rate of Cd sorption by this compound. Results showed the adsorption efficiency is higher in coal slag modified by NaOH 2N compared to NaOH 1N. The kinetic results showed that 80 percent of cadmium was quickly sorbed as the equilibrium time was reached within approximately 60 minutes. Overall, the modification and change in the structure of coal slag could lead to increase the ability of removal and sorption of Cd from aqueous solutions.