Studies On Preparation Of Amino Starch And Its Absorption For Cu(Ⅱ),Cr(Ⅵ)

With the development of modern industry, more and more industry waste water is piping out, which results in the pollution of water. Thus the removal of toxic and polluting heavy metal ions from waste water has received much attention in recent years. Therefore, researches were empHasized on preparing the high-powered chelating adsorption material that could not only remove heavy metal ions from waste water effectively, but also separate and recycle heavy metal ions effectively.In this article, modified heavy metal adsorbents was synthesized with corn starch as raw materials, through the dialdehyde starch reaction with ethylenediamine and loading amino-starch on bentonite. The optimization synthesis condition of dialdehyde starch and amino-starch were determined. And the static state absorbent activity to heavy metals such as Cu²⁺ and Cr(VI) by amino starch and amino starch bentonite blends was studied in terms of adsorptive capacity, adsorptive kinetics, adsorptive isotherm, medium acidity, adsorptive regeneration.The results are as follows:1. The study of dialdehyde starch preparation indicated that reaction temperature and pH were main factors on the impact of aldehyde content. We took the new determination method on aldehyde content- conductivity method, which can deteimine aldehyde content fast and accurately comparaing to the traditional titration. The optimized synthesis conditions were as follows: reaction time 3h, reaction temperature 35℃, pH 1.5-2, sodium periodates concentration 0.6mol / L, and starch sodium periodate molar ratio 1.1:1. And under these conditions, the aldehyde content of oxidized starch obtained to 80%.2. We prepared amino-starch using Dialdehyde starch as raw materials, and studied preparation conditions of amino starch. Ethylenediamine concentration and pH were main factors on the impact of nitrogen content. The optimized synthesis conditions were as follows: reacting time 2h, reacting temperature 35℃, ethylenediamine concentration 0.6mol/L, ethylenediamine dialdehyde starch ratio 4:1. And under these conditions, the nitrogen content of amino starch obtained to 150%, which was nearly twice of the traditional ether method.3. We prepared bentonite amino starch blends for the first time, and confirmed the feasibility of loading amino starch on bentonite. From the IR and XRD spectras of bentonite and amino starch bentonite blends we can find that the lamellar structure of montmorillonite did not change, and amino starch only adsorbed on the internal and external surface of montmorillonite. 4. Adsorption ability of amino starch and bentonite loaded amino starch for Cu²⁺, Cr(VI) were studied. The results showed that: the saturating adsorptive capacity of amino starch to Cu²⁺, Cr(VI) is greater than amino starch bentonite blends; The amino starch adsorption for Cu²⁺ is more fit to the second-order kinetics law, and its adsorption for Cr(VI) is more fit to the first-order kinetics law; the adsorption processes of the two absorbents for Cu²⁺, Cr(VI) are a course of heat adsorption and more fit to Langmuir model; combining with PH on the adsorption properties, we can find that the adsorption process may be surmised chemical adsorption; with diluted hydrochloric acid regeneration agent, amino starch and amino starch bentonite blends can be reused.5. The IR and XRD spectrums adsorbents adsorption of heavy metals before and after shows that, amino starch combined with heavy metal ions by coordination and amino starch bentonite blends combined with heavy metal ions by spectrometer exchange and chelating. The adsorption of the two absents for Cu²⁺ and Cr(VI) belongs to chemical adsorption and mechanisms of the adsorption for heavy metals will be studied furtherly.