Study On Preparation And Characterization Of Activated Carbon From Deinking Sludge

A large number of deinking sludge will be produced during the deinking process of waste paper, and annual pulp consumption in pulp accounted for more than 65% in China,so the production of deinking sludge is huge. The treatment cost of deinking sludge is high,difficult, and harmful to the environment, at the mean time, the deinking sludge is the main solid waste in paper cycle regeneration; activated carbon is an effective adsorbent material,and it is widely used in water treatment, medical care, food production and other fields. The preparation of activated carbon from deinking sludge is environmentally friendly, green,and has profound economic and social significance to achieve the disposal of decrement resource and innocuity about deinking sludge and increase additional value of cycled paper.In this paper, activated carbon was prepared from activated sludge by the method of phosphoric acid activation with deinking sludge as raw material. Through orthogonal experiment and single factor experiment, the optimum preparation conditions were determined as follows: activation time 90 min, activation temperature 450?, impregnation ratio 1:3.5, phosphoric acid concentration of 70%. Under such conditions of preparation,the iodine adsorption value and methylene blue adsorption value of activated carbon is 421.98 mg/g and 10.97 mL/0.1g, respectively; the specific surface area of activated carbon was 715.576 m2/g, the total pore volume was about 0.353 mL/g, and the average pore size was about 18.573 nm which are calculated by the N2 adsorption-desorption experiment.SEM analysis showed that the dissolution of calcium carbonate and other inorganic fillers in activated sludge prepared from deinking sludge which could produce a large pore structure with a diameter of about 1?5?m, which was beneficial to the mass transfer during activated carbon adsorption; XRD analysis demonstrated that the deinking sludge based activated carbon had a rich pore structure; Fourier transform infrared detection of activated carbon showed there are phenolic hydroxyl, carboxyl and other functional groups on the surface, which is conducive to the adsorption of activated carbon; the leaching toxicity test of activated carbon showed that the concentration of the leaching solution was far lower than the maximum allowable concentration of the state, so it is safe and feasible for preparation of activated carbon process from deinking sludge with phosphoric acid.Deinking sludge based activated carbon was used in study of adsorption of Cr(?), and the adsorption conditions were optimized. Under the optimum conditions, that is that the activated carbon dosage is 15 g/L, concentration of Cr(VI) is 150 mg/L, adsorption time is 6 h, the adsorption rate and adsorption capacity of activated carbon on Cr(VI) is up to 87.12% and 8.71 mg/g respectively; the theoretical saturated adsorption capacity and adsorption capacity constant of activated carbon for Cr(VI) were 16.16 mg/g and 0.068 L/g,respectively which were determined by kinetic experiment. Deinking sludge based activated carbon was also used in adsorption of Fe(?), and the adsorption conditions on optimal: activated carbon dosage is 7.5 g/L, concentration Fe(?) 100 mg/L, adsorption time is 3 h, pH=2, under the conditions, the adsorption rate and adsorption capacity of activated carbon on Fe(?) is 89.03% and 11.87 mg/g respectively; experimental study on dynamics of Fe(?) adsorption show that the adsorption capacity is 40.87 mg/g, and the constant of adsorption capacity is 0.029 L/g.The modification of activated carbon was studied according to the application of Cr(?)adsorption, the best modifier is HNO3, concentration of HNO3 is 10 mol/L, the rate of carbon acid to modifier is 1:15(m: V) and the modification time is 2 h. After modification,the dosage of activated carbon was reduced from 10 g/L to 5g/L, and the adsorption rate and adsorption capacity were increased from 56.75% and 8.51 mg/g to 83.89% and to 25.17 mg/g, respectively, furthermore, the adsorption capacity was increased 140.30% compared with that of unmodified activated carbon .The activated carbon was modified and applied to the adsorption of Cr (?), at the same time, the optimal modification conditions were determined as that: modifier is 10 mol/L HNO3.1:15 (m:V), modification time 2 h. When the amount of modified activated carbon was 5 g/L, the removal rate and adsorption capacity were 83.89% and mg/g,respectively,and the adsorption capacity increased by 140.30% compared with that of unmodified activated carbon.