Synthesis And Research The Adsorption Property Of New Adsorbents Based On Starch For Heavy Metal Ions

In recent years, a progressive increase in industrialization and urbanization has substantially enhanced the aquatic environmental pollution by the discharge of industrial effluents containing heavy metal ions. Removal of heavy metal ions from industrial wastewaters has become a major research topic in recent years because excess heavy metals affect the environment and human life by joining the food chain. Adsorption procedures are the most widely used technique for the separation and recovery of heavy metals because of their economic advantages and high efficiency. Starch, as a natural polysaccharide, is biodegradable, abundant and environment friendly. Different approaches are currently used for modifying starch. At present, a common used method is oxidation of starch to dialdehyde starch in the presence of sodium periodate. The present work described the preparation of chemically modified dialdehyde starch with amino compound and studied the adsorption selectivity to heavy metal ions. The adsorbent was characterized by elemental analysis, BET, FT-IR spectra, SEM and XRD. Batch adsorption experiments were carried out as a function of pH, initial ions concentration, contact time and temperature. The adsorption behavior has been further discussed according to isotherm and kinetic models.The main contents of this paper:1. The adsorbents (DASPH) was prepared via the conjugation of dialdehyde starch (DAS) with phenylhydrazine (PH). The effective functions of starch is poor, we employed the oxidation style to modify starch. Three different oxidation degree of starch (DAS1、DAS2、DAS3) were synthetized, so that we can investigate the effect of oxidation on adsorption performance. The dialdehyde starch was prepared by changing the amount of periodate. Then dialdehyde phenylhydrazine starch (DASPH、DASPH2and DASPH3) with different content were generated. The element analysis, BET, FT-IR, SEM and XRD characterization techniques confirrmed the formation of DASPH. The adsorption between Cd(Ⅱ) and dialdehyde phenylhydrazine starch (DASPH) is found to be dependent on the pH of the solution, the initial concentration of Cd(Ⅱ) as well as the contact temperature. The adsorption behavior has been further discussed according to isotherm and kinetic models. The adsorption isotherm studies showed that the adsorption of Cd(Ⅱ) fitted well with Freundlich. The adsorption process was exothermic, lower temperature accelerated it. The adsorption was best fit using the Pseudo-second-order kinetic model.2. Three similar adsorbents were prepared via the conjugation of phenylhydrazine (PH), m-phenylenediamine (MPA) and o-phenylenediamine (PDA) with dialdehyde starch (DAS) and designated as DASPH, DASMPA, DASPDA, respectively. The adsorption properties of the three adsorbents toward metal ions were determined, and the results indicated that DASPH had a good adsorbability to Cd(Ⅱ) among different metal ions. Experimental results revealed that the maximum adsorption capacity of DASPH for the four transition metal ions was as follows:Cd(Ⅱ)(4.9mmol/g)>Zn(Ⅱ)(3.3mmol/g)>Pb(lI)(1.7mmol/g)>Cu(Ⅱ)(0.83mmol/g). The subsequent adsorption-desorption experiment showed that the adsorbent can be recycled.