Investigating arsenic (III and V) continuous flow adsorption by modified calcined mussel shells

Abstract

This study uses modified calcined mussel shells to adsorb arsenic (As(III) and As(V)) in continuous flow tests. It evaluates the adsorbent's effectiveness and regeneration capability over multiple cycles. The experiments used arsenic initial concentrations (I.C.) of 10 and 50 mg/L for breakthrough curve analysis, while reuse and co-ions (Cl⁻, SO₄²⁻, NO₃⁻, HCO₃⁻, and PO₄³⁻) interference tests were conducted at 50 mg/L. Increasing the adsorbate I.C. from 10 to 50 mg/L and the flowrate from 5 to 10 mL/min, while decreasing the adsorbent mass from 10 to 5 g, improved the maximum adsorption capacity for both adsorbates (As(III): 8.99 and As(V): 26.60 mg/g). Conversely, simultaneously increasing the flowrate from 5 to 10 mL/min and decreasing the adsorbent mass from 10 to 5 g accelerated breakthrough. Reusing the adsorbent for five cycles reduced the adsorption capacity by approximately 50 %, emphasizing the need for regeneration or replacement. Competing ions reduced the total arsenic adsorption capacity from 10.43 to 7.62 mg/g and shortened the 50 % breakthrough time from 417 to 305 min. This study also investigated the adsorption performance of mussel shell powder (MP) and mussel shell-coated disc (MD) for contaminant removal. MP exhibited a higher rate constant than MD, indicating faster adsorption kinetics and aligning with its superior adsorption capacity in certain conditions. However, MD demonstrated a higher maximum adsorption capacity. Further studies could investigate the long-term performance and stability of cartridges made from calcined mussel shells, including their lifetime and shelf life.