Preparation and Comparison of Arsenic Removal Granular Adsorbent Based on Iron-Manganese Sludge

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Backwashing sludge is an efficient adsorbent for arsenic removal. However, considering the practical application, it is unfavorable for solid-liquid separation. To overcome this disadvantage, a high-temperature baking method was used to prepare a granular adsorbent (GA) with iron-manganese sludge, along with an embedding method with drying (H-GA) and lyophilization (D-GA). The characterization results showed that the surface of the three adsorbents were rough, with specific surface areas of 43.830, 110.30, and 129.18 m2·g-1, respectively. The adsorption experiments showed that the adsorption of arsenic by H-GA and D-GA was much higher than that of GA. The maximum adsorption capacities of GA, H-GA, and D-GA were 5.05, 14.95, and 13.45 mg·g-1, respectively. The Langmuir model fit the adsorption process of arsenic by H-GA and D-GA better, whereas the Freundlich model fit the adsorption process of GA better. The Pseudo-first order model and Pseudo-second order model were suitable to describe the kinetic curves of the three adsorbents. The acidic environment was more conducive to the adsorption of arsenic. The particle adsorbents prepared by the embedding method, H-GA and D-GA, retained the original structure of iron-manganese sludge, and the specific surface area was much larger than that of GA; thus, the adsorption capacity was greater than that of GA. Drying and lyophilization had no significant effect on the adsorption performance of granular adsorbents prepared by embedding.