Study On Preparation And Adsorption Kinetics For Dye Waste Water Of Porous Carbon Matericals From Waste Cotton Fabrics

The porous carbon materials were prepared from waste cotton fabrics byzinc chloride activation, meanwhile, the preparation conditions andcharacterizations of the porous carbon materials were discussed. The adsorptionperformances and adsorption kinetics of two dyes (Brilliant Crocein andCationic Red2GL) onto it were investigated.With orthogonal experiments, based on the iodine adsorption value,methylene blue adsorption value and phenol adsorption value, the preparationconditions were analyzed. In orthogonal design, multi-index test was used tooptimize the overall adsorption capacity, the optimum process condition wasobtained: the mass fraction of zinc chloride of45%, impregnation time of8h,activation temperature of700℃and activation time of30min. The iodineadsorption value, methylene blue adsorption value and phenol adsorption valueof the porous carbon materials are1198.6mg/g,23.5ml/0.1g, and214.2mg/grespectively.The porous carbon materials prepared from the optimum process conditionfrom waste cotton fabrics were characterized by Nitrogen adsorption-desorptionisotherms, scanning electron microscope (SEM), FT-IR spectroscopy and X ray diffraction to show the specific surface area, pore structure and the physical andchemical properties of the surface. The Nitrogen adsorption-desorptionisotherms result shows that the porous carbon materials possesses a largeapparent surface area (SBET=1462m2/g) and high adsorption pore volume(V=0.78cm3/g) with average pore size diameter of2.14nm, which is rich inmicropores and t-Plot micropore area is50%. SEM images show the surface ofporous carbon materials covers with pores and carves with irregular sizes anddifferent shapes, which includes micro, submicro and nano holes. The results ofthe FT-IR are that the surface of porous carbon materials may contain hydroxylgroups, carbonyl groups and alcohol hydroxyl groups, which suggest the brokenstructure of initial compounds in the activation process. These groups are allhydrophilic and could be the potential active sites for interaction with theadsorbed molecules. At the same time, the XRD analysis show the amorphousform of the porous carbon materials from waste cotton fabrics.The adsorption capacity of different dye molecules onto porous carbonmaterials is different, and Brilliant Crocein and Cationic Red2GL can beadsorbed effectively. Adsorption equilibrium isotherms suggest the processes ofadsorption of Brilliant Crocein and Cationic Red2GL onto porous carbonmaterials are endothermic and the adsorption rate increases with the increases ofexperimental temperature. The equilibrium adsorption capacity increase with theinitial concentration, which the Brilliant Crocein is309.88mg/g and CationicRed2GL is828.55mg/g. The adsorption datas show that adsorptions of eachdye molecule onto porous carbon materials follow pseudo second-order kineticmodel for different experimental temperatures and initial dye concentrations,which includes the processes of liquid membrane diffusion, surface adsorptionand intra-particle diffusion. Meanwhile, the pseudo second-order rate constant k2increases with the decreases of initial concentration and the increases ofexperimental temperature. The above results indicate that the waste cotton fabrics can be activated tohigh adsorption performance porous carbon materials using zinc chloride. Andthe porous carbon materials exhibits higher efficiency in dealing with dye wastewater, which can be employed as an effective, economical and environmentaladsorption material. If the porous carbon materials from waste cotton fabricscould be used in the field of dye waste water treatment, the goal of “using wastetreat waste, recycling economy” can be reached, and the sustainabledevelopment of textile industry can be achieved.