Developing a New Neutralizing Method for the Carcinogenic Hexa-Valent Chromium Compounds in Spent Refractory Chromite Bricks from the Cement Kilns

Regarding environmental pollution cauesed by carcinogenic hexa-valent chromium compounds from spent refractory chromite bricks, a new method for neutralizing of the toxic industrial solid wastes was requested by a group of cement plants. In previous studies, neutralizing methods for toxic chromium compounds were resulted in reduction of these compounds in liquid phase. However, considering the environmental impact of dumping the immense refractory solid wastes of cement kilns, the objective of this study was to install a new procedure for reduction of hexa-valent chromium in solid phase. Considering the novelty of neutralizing the chromium compounds in solid phase, the first part of this study was the exploration of a new reduction procedure by utilizing sugar beet pulp and ferrous compounds, separately and combined together. The second stage was the application of new reduction procedure in a reactor, placed in the outdoor environment. The reactor consisted of a plastic cylinder with diameter of 20 cm with different layers: top layer consisted of clay materials (30 cm in length), second layer was filled with spent refractory chromite bricks mixed with very small amount of ferrous compounds (20cm), third layer was filled with sugar beet pulp (50cm) and the fourth layer was filled with clay (40cm). The reactor was also equipped by a pump for recirculation of leachate and assembled in the outdoor environment during the cold months of winter. Efficiency of reduction of chromium compounds in spent refractory chromite bricks and leachate of the reactor were close to hundred percent. The presented novel procedure for reduction of hexa-valent chromium compounds in spent refractory solid waste could be used for neutralizing toxic industrial waste generated by cement kilns and prevent its environmental impacts. Regarding the availability and low price of sugar beet pulp in close proximity of cement plants, this new method is quite practical, whereupon neutralized solid waste could also be recycled for further uses.