Optimization and regeneration of chitosan-alginate hybrid adsorbent embedding iron-manganese sludge for arsenic removal

[Display omitted] •Provide a new way for sludge disposal in water-treatment plants.•The porosity was optimize by adding NaHCO3 and then heated.•The maximum adsorption capacity of As(III) enhanced.•Regenerate by aerating air into the NaOH solution. The porosity of Chitosan Alginate Fe-sludge Beads strengthened with manganese sludge (CAFBs) was optimized by adding CaCO3 or NaHCO3 powder to generate CO2 gas during the preparation process. Two types of adsorbent Dropped-CAFBs (D-CAFBs) and Heated-CAFBs (H-CAFBs) were made. SEM-EDS, BET, XRD as well as adsorption kinetics and isothermal adsorption experiments were used to evaluate the effects of the two pore-forming methods. The SEM-EDS, BET results confirmed that the prepared adsorbent has good porosity and specific surface area was 128.16m2/g. XRD results showed that the structure is amorphous iron manganese oxide. The pseudo-second, intra-particle and Freundlich model were suitable to describe the adsorption process(R2>0.9), the maximum adsorption capacity of As(III) at 298K is 24.06mg/g. The experiments indicate the pH ranging from 9 to 10 and the air aeration intensity adjusted to 1L/min is favorable for regeneration, the percent of As(III) removal is as high as about 80% after 4 adsorption-desorption cycles.