Cobalt and Phosphorous Recovery from Semiconductor Wastewater through Homogeneous Crystallization of Cobalt Phosphate in a Fluidized-bed Reactor

Semiconductor manufacturing involves distinct processes that generate complex wastewater streams that require treatment before it proceeds to the main wastewater effluents. The present study utilized fluidized-bed crystallization to recover resources from the combined synthetic wastewater of chemical-mechanical polishing and etching processes. The study aims to determine the operational conditions to achieve optimum recovery and removal. Maximum removal and granulation of ~99.0% and 96.07% were realized at pHi range of 7.75 – 8.0 and [PO43-]/[Co2+] ratio of 2.0, respectively. Phosphate concentration in etching stream was reduced from 14.0 mM to [PO43-]d of 1.02 mM at optimal conditions. Uniform crystal size of 0.7 mm dimater was attained at hydraulic rentention time of 15 min, upflow velocity 34.38 – 40.11 m h-1 and surface loadings of 1.18 kg Co2+ m-2 h-1. The granules recovered were cobalt phosphate octahydrate mineral Co3(PO4)2.8H2O as main products as analyzed through XRD analysis. Moreover, SEM-EDS analysis showed ~34.0% Co, ~21.0% P and ~45.0% O having a petal-like structure.