Removal of Heavy Metals Using Bentonite Clay and Inorganic Coagulants

The cost-effective removal of heavy metals from aqueous solution is a major challenge for the scientific community. Heavy metal reduction from aqueous solution using bentonite clay, inorganic coagulants, and their mixture is a cost-effective technique. They are easily available and cheaper compared to the activated carbon, which is widely used but an expensive adsorbent. Bentonite is a clay mineral composed of very fine particles with high opening volume and high specific active site. Thus, it has a significantly high absorption capacity. The metal ion properties, adsorbent dosage, initial concentration, and operating conditions (temperature, pH, contacting time, etc.) are the major parameters for the effective application of raw and modified bentonite. Coagulation is also a traditional technique to minimize metal ions from the bulk solution. Excessive use of inorganic coagulants may result in corrosion and erosion effect on the equipment and excessive generation of sludge volume during coagulation process. Effectiveness of bentonite clay can be enhanced by mixing inorganic coagulants such as sodium carbonate, sulfates and chlorides of aluminum, iron, etc. These coagulants are mixed with the bentonite clay in an optimum ratio to reduce the turbidity and COD of solution. This chapter includes a detailed review of recent work on heavy metal reduction in aqueous system using bentonite clay, inorganic coagulants, and their mixtures.