Study On Surface Characteristics Of Organic Modified Soil And Its Adsorption Peculiarity & Mechanism For Organic And Heavy Metal Pollutants

Using Lou soil as sample, the systematic study on the surface characteristics of organic modified soils (OMS), mechanism of modifying reaction between soils and cationic surfactant cetyltrimethylammonium bromide (CTMAB), adsorption peculiarity and mechanism of modified soils for organic pollutants (OPT) such as phenol or aniline and heavy metal pollutants (HMP) such as Cd2+ or CrO42-, and the adsorption peculiarity of amphoteric surface modified soil (ASMS) for complex pollution of both organic and heavy metals (HM) were conducted. The new opinion and mechanism that the simultaneously adsorption of complex pollution of both organic and heavy metals will be achieved on soil modified with amphoteric surface modifying agent (ASMA), which have both charged group and organophilic group on one ASMA molecule, were proposed at first time, and its rationality was testified at the same time; The 50% was the critical CTMAB modifying ratio of soil CEC at which the organophilic bond (OPB) modifying mechanism was emerged; The thermodynamic characteristics of adsorption of OPT and HMP on OMS were discovered ; The study revealed the surface peculiarity of OMS that the modifying agent were distributed at uneven scatter mode and multi-characters surface were coexisted on surface of OMS, revealed the adsorption peculiarity of OMS that multi-mechanisms were coexisted, confirmed the unequal charge amount modifying mode of OMS in which dual-modifying mechanism of both ion exchange and OPB were processed at the same time, and confirmed that the adsorption hobby to CTMAB was higher than that to Ca2+ on Lou soil. The study conclusions are showed as follows:1. At the same modifying ratio (MR), all the CEC, total acidity, CEC8.2, CECp, surface adsorption density and site density of soils modified with various surface modifying agent (SMA) are lower than that on unmodified soil, the special surface area (SSA) of soil is increased by the effect of cationic SMA, while the effect of anionic SMA has relation with soil layer; CECv decrease and AEC increase in CTMAB modified soil, the reverse trend is found in sodium dodecylsulphonate (SDS) modified soil, and tetramethylammonium(TMA) has little effect on CECv and AEC of soil used. The results show that cationic SMA with long carbon chain (CTMAB) has lager effects on surface characteristics of soil than both cationic SMA with short carbon chain (TMA) and anionic SMA (SDS), the change of surface characteristics are caused by the covering effect resulted from long carbon chain and the negative charge surface of Lou soil. With the increase of MR of CTMAB, all the CEC, total acidity, CEC8.2, CECp, CECv, surface adsorption density and site density of modified soils are descended, but there are some negative adsorption sites on the surface of soil also even though at 200%CEC modifying ratio. The SSA of both layer soil increase in region of MR between 25-100%CEC, and have a little descend trend in region of 100-150%CEC; AEC of both layer soil show the trend that increase in region of MR between 25-100%CEC, and in MR region beyond 100%, AEC of Lou clay layer soil (LCLS) decrease while AEC of Lou tillage layer soil (LTLS) maintain stable. The results show that the 50% was the critical modifying ratio of soil CEC at which the change of modifying mechanism from ion exchange (IE) to organophilic bond (OPB) is emerged.All the CEC, SSA, CEC8.2,CECp of LCLS at same modifying condition are always higher than that of LTLS except CEC8.2 and CECp of 200CB soil sample, but both CECv and AEC show the reverse trend. With the increase of MR of CTMAB, total acidity decrease quickly in LCLS but decrease slowly in LTLS.2. The adsorption isotherms of CTMAB show the linear type at 20℃ and change from linear to H type at 40℃ on both layer soil. The slopes of adsorption isotherm at initial region show the stronger adsorption ability of both layer soil to CTMAB. The isotherms of CTMAB can be divided into two parts, the results that slope of adsorption isotherm at initial region show the contrary vary trend with t...