Chromium is used in different industrial processes such as leather tanning, electroplating, textile dyeing and plastic productions, with the generations of hazardous waste containing relatively high amounts of chromium. In the environment, chromium exists as Cr(III) and Cr(VI) with the hexavalent chromium 100 times more toxic than the trivalent form; exposition to Cr(VI) can causes allergic reactions, asthma eyes irritation, lung and kidney cancer1 . Cr(VI) is highly soluble and mobile in water solution and can be present in different species, depending on its concentration and the pH of the aqueous environment2 . In this context, a transparent silica-based xerogel has been optimized by using sol-gel technique at low temperature (50°C). The disk-shaped xerogel was characterized by Raman, Scanning Electron Microscopy (SEM) and BET measurements. The material showed silica amorphous phase and high porosity and prominent absorption results towards different concentrations of Cr(VI) as HCrO4 − . In addition, the absorption kinetics of Cr(VI) were evaluated by studying different models, showing that the absorption took place by intra-particle diffusion process and the absorption equilibrium followed a Freundlich isotherm model. The xerogel can be reused after the reduction of Cr(VI) to Cr(III), by the treatment with 1,5-diphenylcarbazide.
Cr(VI) ABSORPTION BY SILICA TRANSPARENT XEROGEL MONOLITH: SPECTRAL AND KINETIC STUDY
MARCO ZANNOTTI;ANDREA ROSSI;STEFANO FERRARO;LAURA PETETTA;RITA GIOVANNETTI
2023-01-01
Abstract
Chromium is used in different industrial processes such as leather tanning, electroplating, textile dyeing and plastic productions, with the generations of hazardous waste containing relatively high amounts of chromium. In the environment, chromium exists as Cr(III) and Cr(VI) with the hexavalent chromium 100 times more toxic than the trivalent form; exposition to Cr(VI) can causes allergic reactions, asthma eyes irritation, lung and kidney cancer1 . Cr(VI) is highly soluble and mobile in water solution and can be present in different species, depending on its concentration and the pH of the aqueous environment2 . In this context, a transparent silica-based xerogel has been optimized by using sol-gel technique at low temperature (50°C). The disk-shaped xerogel was characterized by Raman, Scanning Electron Microscopy (SEM) and BET measurements. The material showed silica amorphous phase and high porosity and prominent absorption results towards different concentrations of Cr(VI) as HCrO4 − . In addition, the absorption kinetics of Cr(VI) were evaluated by studying different models, showing that the absorption took place by intra-particle diffusion process and the absorption equilibrium followed a Freundlich isotherm model. The xerogel can be reused after the reduction of Cr(VI) to Cr(III), by the treatment with 1,5-diphenylcarbazide.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
