Investigations On Stucture And Properties Of Inorganic And Organic Anions Intercalated Iron-Containing Layered Double Hydroxides And Their Adsorption Properties For Imidacloprid

In present report, sulfate, dodecylsulfate and dodecylbenzensulfate surfactant anions intercalated iron-containing layered double hydroxides (LDHs) were prepared by using one-step coprecipitation method. The structures and physicochemical properties of the synthesized materials were systematically investigated. The adsorption properties of a non-ionic pesticide imidacloprid over the as-prepared materials were also studied and discussed preliminary. The novelty and major content of the thesis were detailed as follows:Inorganic sulfate-and organic dodecylbenzensulfate-intercalated zinc-iron (â…¡-â…¢) layered double hydroxides were synthesized by one-step coprecipitation method for the first time. The as-synthesized samples have been characterized by XRD,FT-IR,SEM,TEM,TG-MS, Mossbauer spectroscopy (MS),Rietveld analysis and ICP. The combination characterization results revealed that both Fe²⁺ and Fe³⁺ existed in the SO₄^2- contaning product which posses the Green Rust two (GR2) -like crystal structure within an approximate composition of [Zn_0．435 Fe_0．094 ^â…¡Fe_0．470 ^â…¢(OH)₂] (SO₄^2-)_0．235·1．0H₂O, while only Fe³⁺ existed in the DBS-containing one which exhibits the common LDHs compound-like structure. The contact angle measurement indicates the hydrophobic properties of DBS-containing product with the contact angleof 104⁰, compared to strong hydrophilic surface property of SO₄^2- contaning product with the contact angle of 0⁰．Dodecylsulfate and dodecylbenzensulfate surfactant anions were intercalated into zinc-iron and calcium-iron layered double hydroxides (LDHs) by coprecipitation method. The effects of the interlayer anions, as well as the layer charge dencities and the metal within the layers on the crystal structure and the surface properties of the as synthesized materials were systematically investigated. XRD and FT-IR characterizations revealed the well-organized layered structures of the prepared materials. The contact angle measurement indicates the evident hydrophobic properties of the prepared materials. Based on the characterization results, the interlamellar arrangement of surfactant molecules was proposed.Adsorptions of a nonionic organic compounds (NOCs) imidacloprid on the synthesized materials were investigated by batch equilibration techniques, temperature effects on the distribution coefficients (k_r) were also sdudied. The experimental results indicate that Linear equation is fit for the adsorption of imidacloprid on LDHs. The amount of absorbed imidacloprid can be increased due to the interlayer hydrophobic areas of surfactant anions intercalated LDHs. The highly linear adsorption isotherms obtained suggested that the adsorption of pesticides on surfactant anions intercalated LDHs were resulted from partition retention mechanism. The interaction between the surfactant anions intercalated LDHs and imidacloprid includes hydrophobic force, hydrogen force and the van der Waals' force. The sorption parameters of thermodynamics indicate that the adsorption of imidacloprid on DS-ZnFe-LDHs and DBS-ZnFe-LDHs is driven by the decrease of free energy.