Abstract
The wastewaters containing chromium, copper complex, mercury, antimony, thallium or molybdenum individually that was hardly ferritized were pretreated by addition of pulverized iron sulfide. The iron sulfide was in contact with the water adjusted at pH of 7.0 for primarily 6.0h. The resulting slurry was subsequently treated by ferritization at standard conditions, i.e., at pH of 9.0, temperature of 6575°C, reaction time of 1.0h and iron (II) sulfate of 25g to 1l-solution. The concentrations of metallic ions in treated water and in leachate were measured to evaluate the effect of the pretreatment.
The treatment of the wastewaters containing chromium or copper less than 300mg·l-1 was possible by addition of iron sulfide of 2.5g6.3g to 1l-solution. The wastewaters containing mercury or antimony of 30mg·l-1 were also treated by addition of iron sulfide of 2.5g to 1l-solution, but it was necessary to prolong the reaction time to 1.5h for ferritization of antimony. The wastewater containing thallium of 30mg·l-1 was treated by adding iron sulfide of 15g to 1l-solution and by altering the times for sulfidation and for ferritization to 9.0h and 1.5h respectively. In the case of 30mg-Mo·l-1 solution, it was impossible to reduce the concentration of molybdenum to 1.0mg·l-1.
