Study on the Preparation of Mercaptoacetic Acid-modified Heterophylla Shell and Its Application in Separation and Enrichment of Pb2+ in Environmental Samples

To increase the adsorption capacity of the Corylus heterophylla Fisch(HS) for Pb 2+ , HS was chemically modified using NaOH aqueous solution and 95% ethanol and was labeled as SHS; then SHS was chemically modified using mercaptoacetic acid. The SHS modified with mercaptoacetic acid(MHS) was characterized using FTIR, SEM, and XPS. The results indicated that the —SH group was present on MHS, and after Pb 2+ adsorption, the absorption value of the characteristic peak of the —SH group decreased. The adsorption and desorption properties of this functionalized material were investigated as well as the influences of parameters, such as pH value, type of desorption reagent, dosage, flow rate and maximum sample volume. The Pb 2+ adsorption of MHS reached a maximum with pH>5. The experimental data of Pb 2+ adsorption using MHS were fitted using the Langmuir isothermal adsorption model, and a maximum adsorption capacity of 61.54 mg/g was obtained. This was much higher than the adsorption capacity of SHS before modification with the thiol group. After adsorption, MHS was desorbed using a 0.2 mol/L HCl solution, and the percent of desorption was higher than 99%. MHS was used as a solid-phase extractant in the analysis and determination of Pb 2+ content in food and water samples, and the enrichment times achieved 150-fold.