Application Of Amphoteric-cationic And Amphoteric-anionic Combined Modification On Phenol And Cd²⁺ Adsorption Of Yellow Brown Soil

Based on the best modification ratio of adsorption of phenol and Cd²⁺on bentonites modified by a mixture of amphoteric modifier,dodecyl dimethyl betaine?BS-12?and cationic modifier,hexadecyltrimethyl ammonium bromide?CTMAB?,or BS-12 and anionic modifier,sodium dodecyl sulfonate?SDS?,an experiment was designed to prepare amphoteric-cationic and amphoteric-anionic modified soils by two yellow brown soils containing montmorillonite content of 43%and 6%,respectively.The consistency of modification mechanism between co-modified yellow brown soils and bentonites was compared according to the measured surface characteristics of TOC,BET,XRD,FTIR and SEM of yellow brown soils modified by BS-12+CTMAB and BS-12+SDS,the adsorption enhancement effect of combined modification on organic and heavy metal pollutants was verified through the adsorption features of phenol and Cd²⁺under single and complex conditions,the main influencing factor was found combining with the adsorption difference between co-modified bentonites and co-modified yellow brown soils on organic and heavy metal pollutants,the applicability by putting the best modification ratio of adsorption of phenol and Cd²⁺on bentonites into yellow brown soils was proved based on the changes of adsorption effect after adjusting the way of compound modification by comparing with co-modified bentonites.Secondly,based on the optimal modification ratio of phenol and Cd²⁺on co-modified bentonites,an experiment was designed to add a certain proportion of clay minerals?bentonites and kaolin?to change the clay mineral component of yellow brown soils and explore the effect of clay mineral composition on the phenol and Cd²⁺of co-modified yellow browns soils.The effects of changes of clay mineral composition on the modification mechanism,surface characteristics and adsorption effects of co-modified yellow browns soils were studied and the main factors of difference on modification mechanism,surface characteristics and adsorption effect due to the changes in clay mineral composition of yellow browns soils were discussed by comparing with co-modified yellow brown soils.The results achieved in this paper are as follows:?1?Montmorillonite interlayer spacing of two yellow brown soils modified by BS and BS+SDS changed inconspicuous,montmorillonite interlayer spacing of yellow brown soils with higher montmorillonite modified by CT and BS+CT showed different levels of increase as compared with unmodified soils.The total organic content increased with the increment of the proportion of BS,on the basis of amphoteric modification,total organic content improved with the increase of proportion of CT and SDS after compounding CT and SDS,while the specific surface-area decreased with the increase of CT and SDS modification ratio.The results of FTIR and SEM confirmed that BS and CT or SDS were all modified into the structure of yellow brown soils.?2?Based on the basis of the best modification ratio of adsorption of phenol on bentonites modified by BS+CT and BS+SDS,The amphoteric-cationic and amphoteric-anionic modified yellow brown soils were prepared and showed the optimum adsorption capacity for phenol.Compared with yellow brown soils modified by single BS and CT,the BS+CT modified yellow brown soils significantly improved the adsorption ability of phenol.While compared with BS modified yellow brown soils,yellow brown soils modified by BS+SDS decreased the adsorption capacity of phenol,the coexistence of Cd²⁺inhibited the adsorption of phenol.The adsorption isotherms of phenol on the yellow brown soils were suitable for description by Henry model and the adsorption of phenol and the adsorption reflected a negative effect of temperature.The phenol adsorption decreased with increasing pH,but increased with increasing ionic strength.The adsorption thermodynamic parameters of phenol represented a spontaneous and exothermic physical adsorption process.The adsorption capacity depended on the TOC of the modified soil samples mainly,and CEC was the main factor determining the increase of TOC in the soil samples.BS modified yellow brown soils?3?The amphoteric-cationic and amphoteric-anionic modified yellow brown soils were prepared and showed the optimum adsorption capacity for Cd²⁺based on the basis of the best modification ratio of Cd²⁺adsorption on bentonites modified by BS+CT and BS+SDS.BS modified yellow brown soils significantly enhanced the equilibrium adsorption capacity of Cd²⁺,while the adsorption of Cd²⁺on BS modified yellow brown soils was decreased by CT complex modification,and increased by SDS complex modification.Under the Cd²⁺+phenol complex conditions,the coexistence of phenol was unfavorable for the adsorption of Cd²⁺.Langmuir equation very well described the adsorption of Cd²⁺.The adsorption of modified yellow brown soils improved with pH,reduced with ionic strength upgrade.The adsorption thermodynamic parameters of Cd²⁺on BS+CT and BS+SDS modified yellow brown soils were a spontaneous physical adsorption controlled by the characteristics of entropy increment.CEC was the key reason of adsorption difference.?4?With the exaltation of montmorillonite content in yellow brown soils,total organic carbon content,montmorillonite interlayer spacing,intensity of characteristic adsorption peak,and the modification degree of surfactant on the soil surface of the amphoteric-cationic and amphoteric-anionic modified soils all increased,and the reduction degree of specific surface area also heightened as a whole.With the promotion of kaolinite,TOC of soils modified by BS+CT and BS+SDS all reflected a downward trend,montmorillonite and kaolinite layer spacing of BS+CT and BS+SDS modified soils were all not affected by kaolinite content,the degree of specific surface area and peak intensity specific displayed a falling trend as a whole.?5?The adsorption ability of amphoteric-cationic modified soils on phenol was higher than that of amphoteric and single cation modified soils,while the amphoteric-anion modified soils had less adsorption capacity for phenol than that of amphoteric modified soils when adding bentonites and kaolinite to yellow brown soils,respectively.Adsorption characteristics of soils modified by BS+CT and BS+SDS was in consistency with that of amphoteric-cationic and amphoteric-anion modified bentonites and yellow brown soils.The adsorption ability of phenol on BS+CT and BS+SDS modified soils raised when increasing the montmorillonite content of yellow brown soils,and decreased once promoting the kaolinite content of yellow brown soils.The impact of temperature and pH reduced,the impact of ionic strength hoisted,physical adsorption spontaneously increased and the thermal energy required for the reaction diminished with promotion of montmorillonite content.Conversely,The impact of pH and temperature represented an ascendant trend,the ionic strength showed a downward trend,physical adsorption spontaneously displayed a falling trend and the thermal energy appeared an ascendant trend with elevating kaolinite content of yellow brown soils.?6?When adding bentonites and kaolinite to yellow brown soils respectively,the Cd²⁺adsorption on BS modified soils could be decreased by CT complex modification,while increased by SDS complex modification as well as co-modified bentonites and yellow brown soils.The adsorption ability of Cd²⁺on amphoteric-cationic and amphoteric-anion modified soils and the impact of pH reflected an increasing trend with the elevation of montmorillonite content,while manifested a decreasing trend with the promotion of kaolinite content,but the impact of ionic strength decreased gradually with the increase of montmorillonite content and increased with elevating kaolinite content.Physical adsorption spontaneously showed a downward trend with the exaltation of montmorillonite content and denoted an upward trend with elevating kaolinite content of yellow brown soils.The thermal energy required for the reaction of amphoteric-cationic modified soils increased with the increase of montmorillonite content,and decreased once promoting kaolinite content of yellow brown soils,the thermal energy required for the reaction of amphoteric-anion modified soils showed a declining trend with elevating montmorillonite content of yellow brown soils,and appeared an ascendant trend with the exaltation of kaolinite content in yellow brown soils.