Determination of key components and adsorption capacity of a low cost adsorbent based on sludge of drinking water treatment plant to adsorb cadmium ion in water

• Low cost adsorbent based on DWTP sludge was developed to adsorb cadmium ion in water.
• An artificial sludge was synthesized and modified with some components.
• The adsorbent was pH dependent
• Iron oxide and humic substances take an important role in Cd adsorption.
• The modified DWTP sludge should be examined for higher adsorption capacity.

A low cost adsorbent based on sludge of drinking water treatment plant (DWTP), solid waste by-product of sedimentation process in the DWTP, was studied for adsorption of cadmium ion in water. Some parameters such as dose of the adsorbent, pH of solution, and shaking time were investigated in the batch system in order to know the optimum condition and adsorption ability of the adsorbent. Artificial sludge was prepared by following the process of DWTP and the effect of humic acid extracted from the DWTP sludge was examined in order to clarify the key component and adsorption capacity of the adsorbent. This study found that humic acid and iron oxide were the key components of the adsorbent material for adsorption of cadmium ion in water. The Langmuir isotherm adsorption model was fit and the adsorption capacity of the adsorbent based on sludge of Miyamchi and Nishino DWTP for Cd(II) was 5.3 and 9.2 mg/g, respectively. The finding of this study is important for further development of a low cost adsorbent material in the near future.