A green sorbent of esterified egg-shell membrane for highly selective uptake of arsenate and speciation of inorganic arsenic

Abstract

Egg-shell membrane (ESM) is a promising adsorbent for heavy metal uptake. However, carboxylic groups on ESM surface barrier arsenic adsorption. Herein, ESM is modified by esterification and the methyl esterified egg-shell membrane (MESM) possesses positive charge within pH 1–9. As a novel green sorbent material, MESM exhibits 200-fold improvement on sorption capacity of arsenate with respect to bare ESM. It presents an ultra-high selectivity of 256:1 toward arsenate against arsenite. At pH 6, 100% sorption efficiency is achieved for 2μgL−1 As(V) by 10mg MESM, while virtually no adsorption of As(III) is observed. This provides great potential for selective sorption of arsenate in the presence of arsenite. By loading 4.0mL sample within 0.05–5.00μgL−1 As(V) followed by elution with 300μL HCl (1.5molL−1), a detection limit of 15ngL−1 is obtained along with a RSD of 3.5% at 0.5μgL−1. Total inorganic arsenic is achieved by converting As(III) to As(V) and following the same sorption process. This procedure is applied for arsenate determination and inorganic arsenic speciation in Hijiki and water samples. The results are confirmed by graphite furnace atomic absorption spectrometry and spiking recovery.