Preparation of Modified Electrode in situ Carbon Paste Electrode supported by Ni(II) Complex for the Electrochemical Removal of Nitrate from Drinking Water

A new carbon paste electrode modified by NS2 containing Ni(II) complex was prepared for the electrochemical removal of nitrate ions from drinking water. The tripod ligand NS2, namely: Hydro {bis(2-isopropylphenyl-2-thioimidazol-1-yl)(5-phenyl-3-methyl-pyrazol-1-yl)}borate, L, and its mononuclear Ni(II) complex [LNi-NO3] were prepared and characterized in the solid state by infrared (FT-IR), thermal analysis (TA) and in solution by conductivity and 1H NMR. The carbon paste modified electrode was prepared by the immobilization of Ni(II) complex in carbon paste. The prepared electrode was characterized using scanning electronic microscopy (SEM) and cyclic voltammetry (CV). The modified electrode showed only one oxidation peak in the anodic scan at +0.14 V (vs. Ag/AgCl) for the oxidation of Ni(II) complex. Upon addition of nitrate ions, no reduction peaks were observed while the oxidation peak current height for Ni(II) complex was decreased. This decrease in the oxidation peak current can be explained on the basis that a part of Ni(II) complex was consumed in the reduction of nitrate ions to nitrite.