Characterization of composite zeolite-iron modified carbon paste electrode as a tool of iron chromium(vi) detection and its application to liquid waste.

Abstract

Chromium is widely available in nature in two oxidation states which are chromium(III) and chromium(VI). Chromium(VI) is toxic and carcinogenic. Chromium(VI) is a thousand times more dangerous than chromium(III). The presence of chromium in nature is generally caused by industrial processes, such as tannery industry, welding activity, metal polymer and wood preservation industry. Because chromium(VI) has hazardous properties, we need a tool (sensor) that can detect the presence of chromium(VI) and at the same time determine the levels of chromium(VI). The purpose of this study is to develop a tool that can detect the presence of chromium(VI) in the form of composite zeolite–iron modified carbon paste electrode (EPKZB). The carbon paste electrodes are used as a tool of chromium dectection because carbon paste electrodes have many advantages, such as simple construction, a low internal resistance, stable equilibrium between ionic conductor and electricity, a high current exchange, there is no parallel reactions in the main electrode, strength and low cost. Moreover, the carbon paste electrodes can be designed and handled easily. It also can be used in complex sample matrix and easily modified in order to improve electrode performance. Zeolites are used as a electrode modifier materials due to their high adsorption properties which are caused by the presence of cavities or pores. Zeolites used in this study are the natural Cikalong zeolites and A-type zeolite. The A-type zeolite was synthesized from the of natural minerals kaolin. Production of composite zeolite with iron aims to make the surface of the electrode become more positively charged so it can absorb the anion Cr(VI) well. Performance of the composite Cikalong natural zeolite-iron mofified electrode paste electrode (EPKZAB) and composite synthetic zeolite-iron modified carbon paste electrode (EPKZSB) were tested using cyclic voltammetry, with as the reference electrode is Ag/AgCl, as auxiliary electrode is Pt, and as working electrode are EPKZAB, EPKZSB, EPK. Performance measurements were carried out at pH 0.7, 20 minutes of preconcentration time, scanning rate of 125 mVs-1 and using electrolyte solution KCl 0.05 M. Characterization of EPKZAB, EPKZSB and EPK was done by determining linearity, limit of detection measurement, measurement sensitivity, precision measurement, and measurement repeatability. On EPKZAB, EPKZSB, and EPK characterisation acquired the area linearity of the three electrode in the concentration range of 2 μM to 70 μM. Detection limit of EPKZSB, EPKZAB, and EPK 1.48 μM, 1.94 μM and 2.25 μM. Sensitivity of EPKZAB is higher than EPKZSB and EPK lm which is 0.186 μA μM-1, then followed by 0.166 μA μM-1 and EPKZSB 0.154 μA μM-1. EPKZAB , EPKZSB and EPK has moderate measurement accuracy. EPKZAB and EPKZSB has measurement repeatability at a moderate level while EPK had a recurrence at a rate low accuracy. Electrode performance test results on real samples showed that on tannery waste EPKZAB had the best performance, then by followed EPK and EPKZSB by gap measuring difference with UV- VIS 0.50% for EPKZAB, 6.98% for EPK and 57.58% for EPKZSB.