Transforming tire-derived char into powerful arsenic adsorbents by mild modification

A large amount of arsenic-containing wastewater discharged by the non-ferrous metal industry will cause serious environmental problems if it is not properly treated. Pyrolysis char of waste tire is a kind of solid waste. Since the surface properties of tire derived char (TC) are affected by tar/ash adhesion during pyrolysis, it is necessary to modify TC to treat wastewater containing As(V) effectively as an adsorbent. At present, most studies on the modification of TC are prepared into activated carbon by high temperature activation in N₂ atmosphere. In this study, TC was modified at room temperature and air atmosphere, and Fe(OH)₃-TC_NaOH adsorbent with particle size of 61-75 μm was obtained under the premise of the removal rate of As(V) and the settling performance of the adsorbent. When the initial concentration of As(V) was 5 mg/L, the removal rate of As(V) by Fe(OH)₃-TC_NaOH with a particle size of 61-75 μm could reach 90% within 30 min under a wide pH range (3-9). The adsorption of As(V) by Fe(OH)₃-TC_NaOH was most affected by the coexistence of PO₄^3-, which resulted in the removal rate of As(V) decreased by about 20%. The adsorption mechanism shows that the significant increase in the number of 3-5 nm mesoporous pores of Fe(OH)₃-TC_NaOH and the formation of H bonds are beneficial to the adsorption of Fe(OH)₃-TC_NaOH to As(V), and improve the stability of Fe-As complex.