The Esterification Of Egg-shell Membrane For Highly Selective Uptake Of Arsenate And Speciation Of Inorganic Arsenic

Arsenic is a toxic and carcinogenic element, and known as one of the most dangerous element to human health. The investigations have shown that the toxicity of arsenic depends on both its total concentration and its chemical forms. The content and chemical form of arsenic in drinking water is directly related to serious health problems, such as cancer, hypertension, glycuresis, etc. Considering that low content of arsenic and the complexity of substrate in real world samples, it is necessary to perform appropriate sample pretreatment. The separation and preconcentration of ultra-trace arsenic is the basis for the purpose of accurate quantitative analysis.Biosorption materials have been widely employed in the fields of sewage treatment and trace heavy metal preconcentration attributed to its low-cost, wide choice of the materials, various functional groups and favorable sorption capacity. In the present work, carboxylic groups on the surface of egg-shell membrane(ESM) are esterified to achieve improvement on the adsorption capability of As(V). The obtained methyl esterified egg-shell membrane (MESM) is characterized by FT-IR, SEM and Zeta potential(surface charge) analysis.As a novel green sorbent material, the MESM exhibits a 200-fold improvement on the sorption capacity of arsenate with respect to bare ESM. It presents an ultra-high selectivity of 256:1 toward arsenate against arsenite. The adsorption behavior of As(V) and As(Ⅲ) have been thoroughly investigated and the results indicated that the MESM has great potential for selective sorption of As(V) in a wide pH range while virtually no adsorption of As(III) is observed. The adsorbed As(V) can be readily recovered by HCl as eluent.A separation/preconcentration procedure for inorganic arsenic has been developed, As(V) was measured directly by hydride generation atomic fluorescence spectromentry after separation and preconcentration, total inorganic arsenic concentration was achieved after convertion As(Ⅲ) to As(V) and then following the same procedure as that for the quantification of As(V). The concentration of As(Ⅲ) is obtained by difference. By loading 4.0 mL sample solution within 0.05～5.00μg L-1 As(V) followed by elution with 300 μL of diluted HCl, a detection limit of 15 ng L-1(30, n=9) is achieved, and a RSD of 3.5%(0.50μg L’1, n= 7) is derived at 0.5 μg L’1. This procedure is applied for the determination of arsenate and inorganic arsenic speciation in Hijiki and various surface water samples. The results are well confirmed by graphite furnace atomic absorption spectrometry, spiking recoveries are achieved within 95%～102%.