Intensification of adsorption process by using the pyrolytic char from waste tires to remove chromium(Ⅵ) from wastewater

Pyrolysis has the potential of transforming waste into valuable recyclable products. Pyrolytic char(PC) is one of the most important products from the pyrolysis of used tires. One of the most significant applications for pyrolytic char recovered is used for the removal of Cr(Ⅵ) in the wastewater effluent to control waste by waste. The surface chemistry properties of surface element distribution / concentration and chemical structure were examined for the pyrolytic char and the commercial activated carbon(CAC) respectively. The results showed that surfaces of PC possesses a large amount of ester and hydrocarbon graft, whereas there are mainly carbon functional components of C—OH, C O and COOH on the surface of CAC. Therefore the surface electronegativity of PC is lower than that of CAC in the water. The repulsive interactions between the surfaces of PC and the negatively charged Cr(Ⅵ) ion are weaker than that of CAC, which results in an intensification of the adsorption process by the utilization of PC. The adsorption isotherms of Cr(Ⅵ) ion on the two kinds of carbons were determined experimentally. The larger adsorption amount on the PC in the case of Cr(Ⅵ) may be attributed mainly to its special surface micro-chemical environment. The mechanism of the removal Cr(Ⅵ) from aqueous solution was assumed to be the integration of adsorption and redox reaction. The adsorption was the rate-controlled step for Cr(Ⅵ) removal. The adsorption of Cr(Ⅵ) was identified as pseudo-second-order kinetics. The rate constants of adsorption were evaluated.

Application of activated carbon derived from scrap tires for adsorption of Rhodamine B

Activated carbon derived from solid hazardous waste scrap tires was evaluated as a potential adsorbent for cationic dye removal. The adsorption process with respect to operating parameters was investigated to evaluate the adsorption characteristics of the activated pyrolytic tire char （APTC） for Rhodamine B （RhB）. Systematic research including equilibrium, kinetics and thermodynamic studies was performed. The results showed that APTC was a potential adsorbent for RhB with a higher adsorption capacity than most adsorbents. Solution pH and temperature exert significant influence while ionic strength showed little effect on the adsorption process. The adsorption equilibrium data obey Langmuir isotherm and the kinetic data were well described by the pseudo second-order kinetic model. The adsorption process followed intra-particle diffusion model with more than one process affecting the adsorption process. Thermodynamic study confirmed that the adsorption was a physisorption process with spontaneous, endothermic and random characteristics.

Improvement in electrochemical capacitance of activated carbon from scrap tires by nitric acid treatment

Activated carbon （AC） obtained from the industrial pyrolytic tire char is treated by concentrated nitric acid （AC-HNO3） and then used as the electrode material for supercapacitors. Surface properties and electrochemical capacitances of AC and AC- HNO3 are studied. It is found that the morphology and the porous texture for AC and AC- HNO3 have little difference, while the oxygen content increases and functional groups change after the acid treatment. Electrochemical results demonstrate that the AC-HNO3 electrode displays higher specific capacitance, better stability and cycling performance, and lower equivalent series resistance, indicating that AC obtained from the industrial pyrolytic tire char treated by concentrated nitric acid is applicable for supercapacitors.