[Effect of Adding Compound Adsorbent on Phenanthrene and Cr(â ¥) Absorption by Lou Soil].

To study the effect of the addition of compound adsorbent on the phenanthrene and Cr(Ⅵ) adsorption of Lou soil, biochar (made from corn stover) and B200B (Bentonite modified by BS-12, dodecyl dimethyl betaine with modified ratio of 200% CEC of Bentonite) were mixed at mass ratios of 1:2, 1:1 and 2:1 as the compound adsorbents (CS1:2, CS1:1 and CS2:1). Different amounts (2%, 5% and 10%) of these three compound adsorbents were added into Lou soil. Batch method was used to analyze the phenanthrene and Cr(Ⅵ) adsorption isotherms of different Lou samples, and compare the effect of environmental conditions such as pH value and temperature on the phenanthrene and Cr(Ⅵ) adsorption. The results indicated: ① Adsorption amounts of Cr(Ⅵ) on different Lou samples were 3.02 to 13.61 times higher than CK (original Lou soil). Under the same adding conditions (amount), Cr(Ⅵ) adsorption showed the order of CS2:1 Lou > CS1:1 Lou > CS1:2 Lou > CK. Cr(Ⅵ) adsorption was a spontaneous process with decreased enthalpy (except CS1:2) and increased entropy. Adsorption amounts of phenanthrene on different Lou samples were 3.87 to 13.00 times higher than CK. Phenanthrene adsorption presented the ranking of CS1:2 Lou > CS2:1 Lou > CS1:1 Lou > CK at the adding amounts of 2% and 5%, while showed the order of CS1:2 Lou > CS1:1 Lou > CS2:1 Lou > CK when 10% of the compound adsorbent was added. The adsorption was also a spontaneous process with decreased enthalpy and increased entropy. ② When the temperature was 10-30℃, the adsorption amount of Cr(Ⅵ) increased by 5.84%, 4.63% and 8.22% on CK, CS1:1 and CS2:1 Lou soils, and reduced by 2.70% on CS1:2 Lou soils. Adsorption amount of phenanthrene increased by 1.69% of CK and reduced by 10.55%, 4.36% and 12.81% of CS2:1, CS1:1 and CS1:2 Lou soils respectively. ③ When the pH was 4-10, the Cr(Ⅵ) adsorption had no significant change for CK, while those for CS1:2, CS1:1 and CS2:1 Lou soils all reduced. Phenanthrene adsorption of CK, CS1:2 and CS1:1 Lou soils was all highest at pH=4, and phenanthrene adsorption of CS2:1 Lou was highest at pH=7.④ The higher the ratio of B200B in compound adsorbent, the better the phenanthrene adsorption was. The higher the ratio of biochar in compound adsorbent, the better the Cr(Ⅵ) adsorption was.

[Effect of SDS on the adsorption of Cd2+ onto amphoteric modified bentonites].

Under different modified ratios, temperatures, pH and ionic strengths, the effect of sodium dodecyl sulfonate (SDS) on the adsorption of Cd2+ onto bentonites which modified with amphoteric modifier dodecyl dimethyl betaine (BS-12) was studied by batch experiments, and the adsorption mechanism was also discussed. Results showed that the adsorption of Cd2+ on amphoteric bentonites can be enhanced significantly by SDS combined modification, Cd2+ adsorption decreases in the order: BS + 150SDS (BS-12 + 150% SDS) > BS + 100SDS (BS-12 + 100% SDS) > BS +50SDS(BS-12 + 50% SDS) > BS + 25SDS (BS-12 + 25% SDS) > BS (BS-12) > CK (unmodified soil). The adsorption isotherm can be described by the Langmuir equation. The change of temperature effect from positive on CK and amphoteric bentonites to negative on BS + 150SDS bentonites is observed with an increase of SDS modified ratio. The pH has little influence on Cd2+ adsorption on bentonites. The adsorption of Cd2+ on bentonites decreases with ionic strength rise, but the effect of ionic strength can be reduced with an increase of SDS modified ratio also. The adsorption thermodynamic parameters demonstrated that the adsorption of Cd2+ on modified bentonites was spontaneously controlled by entropy increment. When the SDS modified ratio is lower than 100% CEC, the adsorption of Cd2+ on modified bentonites is a process with characteristics of both enthalpy increment and entropy increment, while the SDS modified ratio is equal to or higher than 100% CEC, the adsorption of Cd2+ on modified bentonites becomes a process of enthalpy decrement and entropy increment.