Production of activated carbon from waste bark for effluent treatment in the pulp and paper industry
Nguyen, Trung Thai
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In this study, it is shown that activated carbon can be produced from the bark of Spruce and Jack Pine for use in wastewater treatment. The bark was pyrolyzed in a tube furnace at 1200 of for 2 hrs, and then activated by steam. The activation conditions were varied trom 1200 to 1700 of with residence times of 15 to 60 min. The yield of activated carbon ranged trom 6 to 29 per cent based on original air-dried bark. The activity ot the carbon was determined by measuring the Chemical Oxygen Demand (COD) and color removal from the bleaching effluent of a kraft pulp mill which was treated with various dosages of activated carbon. The adsorptive capacity of the carbon could be increased by increasing the activation temperature and time, with a corresponding reduction in the yield of carbon. At a carbon concentration ot 10 g/l, the powdered carbon could remove up to 70 per cent of the COD and 95 per cent of the coloring materials from the effluent leaving the first caustic extraction stage of a bleach plant which contained 1200 ppm of COD and color transmittance of 50 per cent at a wavelength of 580 mu. At 20 g/l, the reductions were 80 and 98 per cent, respectively, for COD and color. Regeneration of spent carbon by steam treatment was feasible with little loss in either activity or weight.