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Wastewater containing cobalt and copper comprised of plating wash water, plant wash water, and equipment cooling and wash water is generated in the electroplating industry. These metals can be detrimental to humans, animals, plants, and the environment. Thus, it is necessary to treat electroplating wastewater to remove these toxic metals. Carbonate and hydroxide precipitation were utilized for the removal of Co (II) and Cu (II) from synthetic electroplating wastewater by jar tests in this work. The effects of solution pH, precipitant-to-metal ratio, and type of precipitant on the precipitation efficiency of cobalt and copper from the single- and co-contaminated systems were investigated. Carbonate precipitation achieved higher removal efficiency for both target metals in the single- and co-contaminated wastewater streams. Furthermore, it can operate at relatively low pH range of about 7–8. Cobalt in both pollutant systems was almost completely removed at pH 10 using both precipitant systems. Copper was found to be easily removed which was possibly brought about by precipitation-adsorption mechanism. The extent of the co-removal of cobalt with copper is significantly pH dependent. The effect of precipitant-to-metal ratio for cobalt and copper treatment varied in single- and co-contaminated streams. Carbonate precipitation led to higher sludge volume than that of hydroxide precipitation.

In this present study, a novel method to fabricate bimetallic Fe-Co catalyst supported on waste silica was investigated for the photo-Fenton-like (PFL) degradation of Methylene Blue (MB) dye. The uniqueness of this work is on the preparation of the catalyst via fluidized-bed crystallization (FBC) process. Under the optimum conditions of initial pH of 3.0, 3.0 mM of H2O2, and 1.0 g L-1 of FBC-derived Fe-Co/SiO2 catalyst (fFCS), the maximum response for the decoloration and mineralization efficiencies of 20 mg L-1 of MB in 60 min were 100 and 65%, respectively. Compared to the impregnated Fe-Co/SiO2 catalyst, the fFCS catalyst exhibited comparable decoloration and mineralization efficiencies, and relatively lower metal leaching for both iron and cobalt. Superoxide radical was unveiled to be the dominant reactive oxygen species in the PFL system over the fFCS catalyst. The catalysts were characterized by Fourier Transform Infrared spectroscopy, Energy Dispersive X-ray spectroscopy and Scanning Electron Microscopy. The results show the successful incorporation of iron and cobalt on the surface of the SiO2 support material.

The environment is affected by agricultural, domestic, and industrial activities that lead to drastic problems such as global warming and wastewater generation. Wastewater pollution is of public concern, making the treatment of persistent pollutants in water and wastewater highly imperative. Several conventional treatment technologies have been applied to water and wastewater remediation, but each has numerous limitations. To address this issue, treatment using bimetallic systems has been extensively studied. Synergistic effects between the two metals are highly desirable because they usually offer enhanced activity, selectivity, and stability relative to their monometallic counterparts. In this study, a novel method to fabricate bimetallic Fe-Co catalyst supported on waste silica was investigated for the treatment of methylene blue dye as model pollutant. Under the optimum conditions of pHi 3.0, 3.0 mM H2O2, 1.0 g L-1 Fe-Co/SiO2 catalyst, and 20 mg L-1 initial dye concentration, the maximum response for the decoloration and mineralization efficiencies of methylene blue were 100% and 64.57%, respectively. Superoxide radical was unveiled to be the dominant reactive oxygen species in the photo-Fenton-like system over Fe-Co/SiO2 catalyst. Compared to the contrastive catalyst, the Fe-Co/SiO2 synthesized using fluidized-bed crystallization exhibited comparable decoloration and mineralization efficiencies, and relatively lower metal leaching.