Cyclic Adsorption and Desorption Characteristics of Citric Acid-chitosan Variant Resins for Pb, Fe, and Zn Removal from Simulated Mining and Agricultural Wastewater System Read more about Cyclic Adsorption and Desorption Characteristics of Citric Acid-chitosan Variant Resins for Pb, Fe, and Zn Removal from Simulated Mining and Agricultural Wastewater System