Cr(VI) removal from fiber cement process waters: a techno-economic assessment

Abstract

Accumulation of Cr(VI) in industrial fiber cement process water may compromise the product quality and cause health issues. Furthermore, it must be removed from process waters to avoid environmental risks. For this purpose, this work evaluates the potential of advanced nanocelluloses and compare it with the efficiency of conventional adsorbents. The analysis of the industrial process allowed to perform a techno-economic assessment on the long-scale implementation. Among the studied adsorbents, granular (GAC) and powdered activated carbons (PAC) and cationic cellulose nanocrystals (CCNCs) removed >99 % of Cr(VI) from real waters. CCNCs efficiency is linked to their large number of cationic groups. The CCNCs reached adsorption capacities up to 90 times higher than GAC in just 5 min by applying an order of magnitude lower dosages. The cost analysis of GAC adsorption revealed that the ultrafiltration and reverse osmosis treatment of backwashing water costed up to 9.5 US$·m−3. To minimize the generated hazardous wastes, the application of evaporation or a second UF and RO treatments reduced costs in 66 % and 71 %, respectively. The use of high-performance membranes and achieving discounts on GAC purchase, 1.6 US$·m−3 would be reached. This suggests that the CCNCs competitive price would be below 22 US$·kg−1.