Ferrochromium and chromium based compounds are produced worldwide from chromite ore. Chrome
chemicals are from chromium based compounds. Basic-chromium-sulfate (BCS) is a chrome chemical
mostly required as main tanning agent in chrome tanning process in leather industry and also to synthesize
other chromic compounds. During the preparation of basic-chromium- sulfate, sodium dichromate
containing chromium (VI) is reduced to chromium (III) by sulfur-di-oxide in a packed tower at a
chemical process industry (B&M Chemicals, India) where the BCS is produced at suboptimal efficiency
due to inefficient (suboptimal) absorption of sulfur-di-oxide (as the gas enters the tower at a higher
temperature) followed by reaction. Improper reduction leads to the presence of unconverted chromium
(VI) that imparts toxicity, not only through product basic-chromium- sulfate but also through leather and
articles produced using this chemical. Design and operating conditions of the packed bed absorber were
found and effects of pH, temperature and concentration of SO2 on the performance of absorption were
studied. The reaction is favored at pH 4. The overall efficiency of conversion in the tower is increased
from 70% to 80% by operating the column at optimal operating conditions obtained using response
surface method. Dispersion is achieved by random packing that provides complex countercurrent flow
path resulting in greater probability of entraining gas inside the tower. Profiles of basic chromium sulfate
are obtained along the height of the tower by solving mathematical models of the reactive absorption
process. Chromium (VI) is 99% reduced to chromium (III) in the product. Leached residues and liquid
wastes are treated with either ferrous sulfate or sodium sulfide to convert chromium (VI) to chromium
(III) to provide sustainable technology. Treated solid waste is stored before safe disposal in hazardous
landfill facility. As chromium (VI) is highly toxic, several sustainable methods are suggested to eliminate
it from effluent to provide cleaner and sustainable production environment in the industry.