Adsorption Of Methylene Blue And Cadmium Ions By Surfactant Modified Activated Carbon

The dyeing wastewater contains a large amount of dyes,heavy metals,surfactants and other pollutants,and greatly affects the water body health and the microorganisms in the water environment.The adsorption method is considered as a better wastewater treatment technology due to its advantages such as environment friendly,high efficiency,simple operation,and no secondary pollution.Research on surfactant-impregnated modified activated carbon showed that the modified activated carbon can not only enhance the adsorption capacity of ionic pollutants on activated carbon,but also can promote the selective adsorption.Studying the adsorption of dyes and heavy metals by surfactant-modified activated carbon provides a new idea for the treatment of printing and dyeing wastewater.In this paper,the enhanced adsorption of methylene blue?MB?dye ion and cadmium ion?Cd????on the activated carbon?AC?modified by three surfactants in aqueous solution was researched.Anionic surfactants-sodium lauryl sulfate?SLS?and sodium dodecyl sulfonate?SDS?and cationic surfactant-hexadecyl trimethyl ammonium bromide?CTAB?were used for the modification of AC.The optimum condition for modification of AC by surfactants was investigated through orthogonal experiment.The modification time of 4 h,reaction temperature of 28?and modifier concentration of 1 critical micelle concentration?CMC?were the optimum conditions for modified.The powder activated carbon modified by anionic/cationic surfactant was used for the adsorption of MB dye wastewater.The results showed that the adsorption performance of cationic dye by activated carbon modified by anionic surfactants?SLS-PAC?was significantly improved,whereas the adsorption performance of cationic dye by activated carbon modified by cationic surfactant?CTAB-PAC?was reduced.In addition,the effects of initial MB concentration,AC dosage,p H,reaction time,temperature,real water samples,and additive salts on the adsorption were studied.Experimental data showed that the adsorption equilibrium time was 120 min,and the adsorption capacity increased with the increase of p H.It was found that the isotherm data had a good correlation with the Langmuir isotherm through analyzing the experimental data by various models.The theoretical maximum adsorption capacity of MB on SLS-C,obtained by the Langmuir adsorption isothermal equation fitting,was up to 232.5mg.g^-1,whereas the theoretical maximum adsorption capacity of Virgin-C was 153.7 mg.g^-1.The dynamics of adsorption were better described by the pseudo-second-order model and the adsorption process was endothermic and spontaneous.When Na⁺,K⁺,Ca²⁺,NH₄⁺,and Mg²⁺were present in the MB dye solution,the effect of these cations was negligible on the adsorption?<5%?.The presence of NO₂^-improved the adsorption performance significantly,whereas the removal rate of MB was reduced in the presence of competitive cation(Fe²⁺).The results showed that SLS-PAC was effective for the adsorption of MB dye in both modeling water and real water.In order to study the influence of different activated carbon materials,four types of granular activated carbon?husk,wood,coal,coconut shell?modified by anionic/cationic surfactant was used for the adsorption of Cd???in aqueous solution.The experiment showed that coconut shell activated carbon has a larger Cd???adsorption capacity than other activated carbons,and the smaller the activated carbon particle size,the greater the adsorption capacity.Activated carbon modified by anionic surfactant?SLS-GAC?can significantly improve the adsorption performance of Cd???,whereas cationic surfactant?CTAB-GAC?has an inhibitory effect on Cd???adsorption.The optimum experiments conditions on the adsorption of Cd???were investigated.Under the conditions of reaction time of 300 min,reaction temperature of25?,the initial p H of 8 and adsorbent dosage of 1 g.L^-1,the adsorption capacity of Cd???on SLS-GAC was reached 9.35 mg.g^-1,which was 1.8 times of that on unmodified activated carbon.The adsorption process of Cd???by SLS-GAC was an endothermic and spontaneous.The presence of Na⁺and K⁺ions has a negative effect on the adsorption of Cd???by SLS-GAC,and the Na⁺/K⁺two-ion component system would enhance the inhibitory effect.The adsorption of Cd???by SLS-GAC in real water samples proved the negative effect of the presence of ions on the adsorption of Cd???.The characteristics of simultaneous adsorption of MB and Cd???by SLS-GAC in two-component system were necessary to studied.It was found that the removal rate of MB was almost unaffected in the presence of Cd???,but the removal rate of Cd???was inhibited in the presence of MB.When the MB concentration was 100 mg.L^-1,the removal rate of Cd???in two-component system was only 37.3%of that in the one component system.This study showed that AC modified by SLS has a better adsorption performance for MB and Cd???,while AC modified by CTAB has a worse adsorption performance for MB and Cd???compared to the Virgin AC.The conclusions of this paper provide an idea for the preparation of environmental functional material for the treatment of dyeing wastewater.