Modified fly ash as an effect adsorbent for simultaneous removal of heavy metal cations and anions in wastewater

A novel fly ash-based composite material with multiple adsorption sites was synthesized to remove Pb2+, Cd2+ and AsO33-from wastewater. In a single pollutant system, when pH = 6, the initial pollutant concentration was 100 mg/L, and the dosage was 4 g/L, the removal rates of Pb2+, Cd2+ and AsO33-by modified DTCH-MFA were increased by 54.4 %, 2.14 % and 6.44 % compared with the unmodified FA. For DTCH-MFA, the maximum adsorption capacities of Pb2+, Cd2+ and AsO33-were 15.86 mg/g, 3.74 mg/g and 5.63 mg/g, which increased by 14.04 mg/g, 0.28 mg/g and 1.87 mg/g than FA. In the actual wastewater system, DTCH-MFA could simulta-neously remove Pb2+, Cd2+ and AsO33-with removal rates of 85.31 %, 95.98 % and 47.57 %. The relevant adsorption mechanisms were studied via XRD, FTIR, VSM and XPS, which revealed electrostatic interaction, and chelation reaction played important roles to the efficient adsorption. Besides, the adsorption processes were consistent with the Pseudo-second-order Kinetics and Freundlich isothermal model. DTCH-MFA could simulta-neously adsorb Pb2+, Cd2+ and AsO33-within 2-8 h, which extended the related studies on the removal of heavy metal cations and anions by FA-based adsorbents.

Automated summary

A novel fly ash-based composite material, modified DTCH-MFA, was synthesized for effective removal of Pb2+, Cd2+ and AsO33- from wastewater. In a single pollutant system, the removal rates of Pb2+, Cd2+ and AsO33- by modified DTCH-MFA were significantly higher compared to unmodified FA. The maximum adsorption capacities of Pb2+, Cd2+ and AsO33- by DTCH-MFA also showed significant improvement. In the actual wastewater system, DTCH-MFA exhibited simultaneous removal of Pb2+, Cd2+ and AsO33- with high removal rates. The adsorption mechanisms were studied and found to involve electrostatic interaction and chelation reaction. The adsorption processes followed Pseudo-second-order Kinetics and Freundlich isothermal model. DTCH-MFA extended the scope of FA-based adsorbents for simultaneous adsorption of heavy metal cations and anions within a short time period.