Adsorption Properties And Extraction Application Of As-synthesized Masoporous MCM-41

Although many instrument analysis methods possessing high sensitivity andselectivity have been developed recently，Pre-concentration and analysis of traceanalyte in samples with complex metrix before the accurate measurement by theinstruments in reality is still a rigorous chanllenge of analysis science. Currently, themost widely used method for the enrichment and separation of trace elements andorganic compound in the sample solutions is the solid phase extraction technique,for its convenience and efficiency. The confined tamplates in the as-synthesizedmesoporous samples are unique resources to dissolve organic molecules, whichmakes the as-synthesized mesoporous samples may have potential applications assolid-phase extractants.We used cetyltrimethylammonium bromide（CTAB） and ionic liqud1-alkyl-3-methylimidazolium salts([C₁₆mim]Br) as the template and tetraethylorthosilicate（TEOS） as the silica source for the synthesis of CTAB-MCM-41and[C₁₆mim]Br-MCM-41. The properties of synthesized samples were characterizedwith XRD low angle, N2adsorption-desorption and IR analysis. The adsorption ofphnols and2,4-dichlorophenoxyacetic acid（2,4-D） and the solid phase extractionapplication to enrich2,4-D of as-synthesized MCM-41were investigated in thiswork. The extent of adsorption of2,4-D was investigated as a function of solutionpH, reaction temperature and supporting electrolyte （sodium chloride） concentration.Langmuir and Freundlich isotherms were used to model the adsorption equilibriumdata.The as-synthesized MCM-41showed very high adsorption capacity for theanalytes with rapid speed. The MCM-41without template did not show significantaffinity for the analytes. The key factor leading the differences is the excellentAdsolubilization performance of template inside MCM-41. The adsorption of2,4-Dby both as-synthesized CTAB-MCM-41and as-synthesized [C₁₆mim]Br-MCM-41are exothermal. acidic condition, room temperature are favorable to the adsorption.The adsorption of2,4-D by as-synthesized CTAB-MCM-41synthesized byhydrothermal method is well fitted using Freundlich isotherm model and theadsorption capacity is42.80mg/g. Using the as-synthesized CTAB-MCM-41assolid-phase extractants developed a solid-phase extraction method. Its quantitativedetermination is of the scope of3.0-25.0mg/L and the enrichment factor is33.33.When the sodium chloride concentration in the solution is lower than0.05g/L, theimpact is very small for solid-phase extraction. The proposed method was applied tothe detennination of trace2,4-D in tap water and Songhua River water samples with the recovery ratio ranging between71.00%-99.29%and RSD ranging between2.36%-9.31%. The results proved that the as-synthesized MCM-41really is aexcellent solid-phase extractants and provides a new absorbent to enrich andseparate trace2,4-D.The adsorption of2,4-D by as-synthesized [C₁₆mim]Br-MCM-41synthesizedby Sol-gel method is well fitted using Langmuir isotherm model and the adsorptioncapacity is113.54mg/g. Using the as-synthesized [C₁₆mim]Br-MCM-41as solid-phase extractant developed a solid-phase extraction method. Its quantitativedetermination is of the scope of0.3-6.2mg/L and the enrichment factor is25. Whenthe sodium chloride concentration in the solution is lower than0.05g/L, the impactis still great for solid-phase extraction. But the results can not meet the requirementsfor analysis when the proposed method is applied to the determination of trace2,4-Din tap water and Songhua River water samples.