A batch experiment was conducted to investigate the adsorption of an acid dye(Acid Orange 51) and a basic dye(Safranine) from aqueous solutions by the sludge-based activated carbon(SBAC). The results show that the adsorption of Acid Orange 51 decreases at high p H values, whereas the uptake of Safranine is higher in neutral and alkaline solutions than that in acidic conditions. The adsorption time needed for Safranine to reach equilibrium is shorter than that for Acid Orange 51. The uptakes of the dyes both increase with temperature increasing, indicating that the adsorption process of the dyes onto SBAC is endothermic. The equilibrium data of the dyes are both best represented by the Redlich-Peterson model. At 25 °C, the maximum adsorption capacities of SBAC for Acid Orange 51 and Safranine are 248.70 mg/g and 525.84 mg/g, respectively. The Elovich model is found to best describe the adsorption process of both dyes, indicating that the rate-limiting step involves the chemisorption. It can be concluded that SBAC is a promising material for the removal of Acid Orange 51 and Safranine from aqueous solutions.
To obtain the pyrolysis characteristics and kinetics of preparation process of sludge-based activated carbon by ZnCl2activation method( i. e. the pyrolysis process of the sludge with ZnCl2activation),the characteristic of mass loss and gas products generated during pyrolysis of the sludge with ZnCl2activation were analyzed by thermogravimetric analysis coupled with Fourier Transform Infrared Spectroscopy( TG-FTIR). The kinetic parameters were calculated by the Coats-Redfem method and the mechanism models were established.The role of ZnCl2in the pyrolysis process of the sludge with ZnCl2activation was also illustrated through the comparison of the pyrolysis characteristics and kinetics of the sludge with and without ZnCl2activation. The results showed that the pyrolysis process of the sludge with ZnCl2activation can be divided into four stages including the dehydration of sludge and initial depolymerization of a small portion of organics matters,the decomposition of large molecular organic matters into small molecular intermediates,the further degradation of intermediates and volatilization of ZnCl2,and the decomposition of inorganic minerals and undecomposed organic matters. CO2,CO,CH4,H2O,some aldehydes and carboxylic acids are the major pyrolysis gaseous products. The activation energies and pre-exponential factors are in the range of 28. 84- 206. 42 kJ / mol and9885. 16-8. 08 × 1011min-1,respectively. During the pyrolysis of sludge,ZnCl2not only can function as a dehydration agent and inhibit the formation of tar,but also can peptize the organic matters in the sludge,making them easier to be decomposed.
