Cadmium and lead removal from aqueous synthetic wastes utilizing Chemelec electrochemical reactor: Study of the operating conditions

Abstract

The enormous production of highly polluted water co-produced with oil and gas over the world represents an important issue of environmental concern and therefore, treatment is required before being discharged into natural aquatic systems or re-used in other processes. Here, we present a hydrodynamic characteristics study of a scale bench electrochemical reactor of parallel plates with inert fluidized bed and its use for the removal of cadmium and lead ions from aqueous synthetic wastes. Initially, the operation conditions were optimized and the terminal velocity, Reynolds number and the Richardson and Zaki coefficient, were calculated. Under laminar flow regime, the experimental fluidization conditions were of a special type, and the minimum fluidization velocity showed a discrepancy with the theoretical ones, given that these semi-empirical relations were established for gaseous fluid and cylindrical reactors configuration which are not the same case of our study. The presence of the fluidized bed increased the dispersion degree for all flow rates studied. The best coefficient of dispersion (0.07) was achieved using 150g and 800Lh−1 of fluidized bed mass and flow rate, respectively. The reduction of lead ion revealed to be diffusion-controlled, while the cadmium reduction was given by the electroreduction kinetics. Removal percentages higher than 99.0% were achieved for Pb and ∼94.0% for Cd when studied separately. However, although the Pb removal remains higher than 99.0%, there was a decrease in the Cd removal when both ions were used in the same solution, maybe because the electrodeposition of cadmium can occur onto previously deposited lead.