Preparation And Process Research Of Chitosan Adsorption Materials For Heavy Metal Ion Adsorption In Water

Heavy metal pollution has become one of the most pollution and harmful to human beings.At present,the common treatment methods of heavy metal ions in wastewater include chemical precipitation,adsorption,redox,ion exchange and so on.Among them,the adsorption method has been widely applied to the treatment of heavy metal ions due to its advantages of simple operation,low cost and little secondary pollution.For the adsorption method,the key is the choice of adsorbent.Among many adsorbents,chitosan as an environmentally friendly biosorbent has been widely researched.The aim of this study is to introduce more active sites or make chitosan itself exposed more active groups,to rapidly and efficiently remove heavy metal ions by chitosan.Specific research work includes the following:In the first part,a novel kind of chitosan-based bead was prepared from chitosan(CS)as the main adsorbent material,sodium phytate(SP)and epichlorohydrin(ECH)as ion chelator and covalent cross-linking agent,respectively.The structure of the beads was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy,respectively.The adsorption properties of the beads for Cu(Ⅱ)ions under different adsorption conditions were investigated.The maximum adsorption capacity of Cu(Ⅱ)ions was 177.1 mg/g.The adsorption isotherm of Cu(Ⅱ)ions on the CS/SP/ECH beads was well correlated with the Langmuir isotherm model,and the whole adsorption process could be better followed the pseudo-second order kinetic model.Moreover,the CS/SP/ECH beads still exhibited good adsorption capacity even after the fifteenth regeneration cycles.In the second part,a homogeneous adsorption behavior of chitosan on single system and binary metal ion system was explored in order to further improve the adsorption capacity and adsorption efficiency of chitosan for heavy metal ions.The result showed that the maximum adsorption capacities for Cu(Ⅱ)and Ni(Ⅱ)ions were 450 and 384 mg/g,respectively.These values were five and eight times as much as pure CS resin reported,showing a high performance/price ratio although no regeneration.The homogeneous adsorption of chitosan for Cu(Ⅱ)and Ni(Ⅱ)ions followed the Langmuir model and the pseudo-second order kinetic model.In the third part,chitosan composite membrane modified by sodium phytate was used to adsorb trace heavy metal ions under the electric field.CS/SP/PET composite membrane was successfully prepared by PET nonwoven fabric as a support membrane.The influences of the electrode voltage,electrode spacing and flow rate on adsorption capacity of CS/SP/PET composite membrane for copper ions were studied.The results showed that the removal rate was up to 88%at the conditions of applied voltage of 1.2 V,electrode spacing of 2.0 mm,flow rate of 5 mL/min.Compared with no voltage applied,the removal rate increased by 32%.