In this study, ZnCl2, H3PO4, and FeCl3 were used as activating agents to prepare porous carbons (PC-ZnCl2, PC-H3PO4, and PC-FeCl3) from cotton textile wastes at a relativity low temperature. The morphology and structure of carbons were characterized by SEM and XRD demonstrating that carbons with porous property were successfully obtained. Textural properties showed that the PC-ZnCl2 possessed the largest specific surface area of 1854.70 m2 g-1 with mesopores domination. Both of micropores and mesopores existed in PC-H3PO4. Micropores were well developed in PC-FeCl3, and the proportion of which was the highest. The FTIR and pHpzc analysis indicated that all the carbons had acidic characteristics, and more acid functional groups were appeared on the PC-FeCl3 than others. The different pyrolysis activation paths were proposed by the thermogravimetric analysis, which proved that the addition of activating agents promoted the formation of pores, lowered the pyrolysis temperature of cotton textile wastes, and inhibited the production of volatiles. The results of adsorption kinetics and isotherm revealed that PC-ZnCl2 exhibited the best adsorption capacity of Cr(VI), and chemical adsorption played a significant role. Meanwhile, surface functional groups of porous carbons also participated in the Cr(VI) adsorption via electrostatic interaction and reduction reaction. Graphical abstract.
Keywords: Adsorption; Cotton textile wastes; Porous carbon; Pyrolysis-activation.