High catalytic activity of Fe(II)-clinoptilolite nanoparticales for indirect voltammetric determination of dichromate: Experimental design by response surface methodology (RSM)

A novel, simple, cheap and very sensitive modified carbon paste electrode (CPE) was used for indirect determination of dichromate in aqueous solution. Peak current of Fe(II) redox system exited form Fe(II)-exchanged clinoptilolite nanoparticles modifier (Fe(II)-NClin) at the surface of CPE was decreased in the presence of dichromate. Hence, this decrease in peak current was used for indirect determination of dichromate. Raw and modified zeolite and CPE were characterized by XRD, FT-IR, SEM-EDX, BET, X-ray map, electrochemical impedance spectroscopy (EIS) and TEM techniques. EIS results confirm that the Fe (11)-NClin/CPE has the best charge transfer efficiency with respect to raw CPE and NClin/CPE. To study the effects of more influencing experimental variables (such as modifier% and loaded of Fe(II), solution pH and scan rate) and reducing numbers of experiments experimental design was applied by response surface methodology (RSM). Under optimum conditions, the current response of Fe(II)-NClin/CPE was inversely proportional to Cr2O72- in the concentration range from 2.0 x 10(-9)-4.0 x 10(-3) mol L-1 with a DL of 1.1 x 10(-11) mol L-1. (C) 2016 Elsevier Ltd. All rights reserved.