Adsorption of Lead Metal Ions in Solution with Diphenylcarbazide Modified Silica Gel

Abstract

Silica gel is one of the adsorbents whose surface is easy to modify and can be used in the adsorption of heavy metal ions. This study aims to modify silica gel with diphenylcarbazide and use it as an adsorbent for Pb2+ metal ions. The modification was carried out by impregnation of silica gel with diphenylcarbazide solution at a ratio of 1 gram of silica gel and 1 mmol of diphenylcarbazide. Characterization with IR spectrophotometry to analyze the functional groups formed on the modified silica gel and the initial silica gel, acid-base titration to determine the surface acidity, and methylene blue method to determine the surface area of ??the two silica gels. . The results showed that the modification of silica gel with diphenylcarbazide had been successfully made, indicated by the appearance of the absorption band of the N-H group at ±3375.43 cm-1, aromatic C-H at ±3032.10 cm-1 and C=O at 1658.78 cm-1. , which are groups derived from diphenylcarbazide, and the absorption band of the Si-O-Si group at ±1203.58 cm-1, the Si-OH group at 912.33 cm-1, and the –OH group in the wave number range of 3600 -3400 cm-1, which is the main group of silica gel. Diphenylcarbazide-modified silica gel experienced an increase in surface acidity from 0.5205 to 0.8133 mmol/g, and a slight increase in surface area from 46.1057 to 46.1613 m2/g. Adsorption of diphenylcarbazide modified silica gel on Pb2+ metal ions in optimum solution occurred at pH 3, contact time 10 minutes, and initial concentration of Pb2+ 300 mg/L, with an adsorption capacity of 52.6264 mg/g. The adsorption that occurs follows the Langmuir isotherm.