Document Type : Research Paper
Postgraduate Program in Process Engineering and Technologies (PEGEPROTEC), University of Caxias do Sul, Caxias do Sul, Brazil
Postgraduate Program in Process Engineering and Technologies (PGEPROTEC), University of Caxias do Sul, Caxias do Sul, Brazil
The effluents from galvanotechnical processes contain toxic metals and recalcitrant substances. In the last few years, the restrictions on the quality of these effluents before release into the environment have intensified. A possible resolution for this problem is employing membrane separation processes, such as reverse osmosis, as a part/step in the treatment of this kind of effluent. This study aimed to analyze two strategies to enhance the performance of a galvanic treatment system. Strategy A was composed of physical-chemical treatment, advanced oxidation, simple filtration, and an ion exchanger, with the implementation of reverse osmosis in the existing process. Strategy B consisted of the substitution of the ion exchanger by reverse osmosis. It used a polysulfone RO membrane supported in polyamide. The efficiency of the proposed strategies regarding the environmental parameters for the disposal of the treated effluents was analyzed. The obtained results showed for strategies A and B removal of 99.45 % and 98.90 % for Ni, 99.96 % and 99.86 % for Cu, 99.77 % and 99.36 % for Zn, 98.16 % and 95.00 % for chemical oxygen demand, 94.13 % and 94.24 % for ammoniacal nitrogen, and 100% for total suspended solids, respectively. About 80-90 % of the starting transmembrane flux was restored in both strategies after chemical cleaning, but irreversible fouling also occurred. Total blocking was the main fouling mechanism observed, regardless of the strategy. The effluents treated using both strategies complied with the environmental parameters for the disposal of galvanic effluents, allowing for the substitution of a step in the process (strategy B). However, strategy A, due to the ion-exchange step, was more effective since it yielded lower final concentrations of heavy metals in the treated effluents. The ion-exchange step helps reduce the number of chemical cleanings and operational costs, increasing membrane lifespan, and reducing environmental impacts because of the smaller amounts of metal ions present in the treated effluent.