Removal Of Cobalt From Cobalt Oxide Production Wastewater

The wastewater from cobalt oxide production process contains high concentration of ammonia nitrogen, organic extractant agent and certain concentration of cobalt. If discharged without appropriate treatment, it would bring about serious pollution to the environment and endanger human heath severely. At present, there are many treatment technologies such as precipitation, adsorption, ion exchange, membrane process, biological technology, extraction and so on. Precipitation is the most widely used process among these technologies. However, because cobalt ion could form metal-complexes and metal-chelates with ammonia nitrogen and extraction agent, effluent of cobalt concentration treated by chemical precipitation process could not comply discharge standard.In order to develop an effective method for cobalt removal, ion exchange process and ferrite process, and the effect of different factors on cobalt removal from simulated wastewater was investigated. It was found that D1100resin had a strong adsorption capacity for cobalt at high ammonia concentration solution; energy consumption was lower and sludge setting was better by transforming sludge. The results are as follows:(1) The saturation adsorption capacity of cobalt on D1100resin is200mg·g-1, with pH from2to7at25℃. The adsorption behavior of cobalt on D1100resin is based on Langmuir equation,(2) The adsorption kinetics of cobalt on D1100resin is fitted to pseudo-second-order model. The effect of Na+and Ca2+on adsorption behavior of cobalt on D1100resin is little. However, ammonia nitrogen and extraction agent have negative influence on adsorption of cobalt, which decreased adsorption potential of cobalt on D1100resin, the adsorption ability of cobalt on D1100resin was decresed.(3) The effluent cobalt concentration from the actual wastewater could reach the standard (GB25467-2010) after treated by stripping and ferrite process, with initial cobalt concentration lower than50mg·L-1, ammonia nitrogen concentration lower than6000mg·L-1, reaction pH value above9, Fe2+ dosage of300mg·L-1, reaction time of30min, sludge conversion time of20min, sludge conversion pH value at12. The number of figures, tables and references are41,21,85.