Adsorption Of Heavy Metal Ions By PET Nonwoven Fabric Treated With Chitosan Composite Gel

Based on the characteristic of chitosan to adsorb heavy metal ions,a composite gel is first prepared by using chitosan,citric acid and glutaraldehyde and/or by adding microcrystalline cellulose,and then applied to needle punched PET nonwoven fabric.The modified PET nonwoven fabric is endowed with the capability of adsorbing heavy metal ions and can be used repeatedly.The scheme to process PET nonwoven fabric is optimized according to the single factor analysis method.The behaviors to adsorb heavy metal ions by the modified PET nonwoven fabric are measured and the mechanisms are also discussed.Prior to use,PET nonwoven fabric is etched by alkali solution,thus some active groups can be produced on the surface of PET fiber and a few of pits are also formed.In the first part,PET nonwoven fabric is treated with chitosan composite gel,and then sprayed by a layer of tetrabutyl titanate solution on the basis of single factor analysis.Titanium dioxide nanoparticles are produced on fabric surface after being boiled in hot water.In the second part,microcrystalline cellulose is added into the chitosan composite gel,and then applied to PET nonwoven fabric.The optimal amount of cellulose is given.The abilities to adsorb heavy metal ions such as copper,chromium and manganese by PET nonwoven fabric are measured by means of the spectrophotometry method.The adsorption isotherm and adsorption kinetics experiments are investigated.Finally,the surface morphologies,chemical compositions,structural changes and thermal properties of PET nonwoven fabric before and after treatments are characterized by scanning electron microscopy?SEM?,X-ray energy dispersive spectroscopy?EDS?,X-ray diffraction?XRD?,infrared spectroscopy?IR?and thermogravimetric?TG?analysis techniques.The results show that,?1?The optimal process conditions of PET nonwoven fabric using chitosan composite gel are as follows:1.5 g of chitosan?degree of deacetylation 95%?is first dissolved in 60ml of 8%acetic acid solution,and magnetically stirred for 2 h.1.2 g of citric acid,1.2 g of sodium hypophosphite,and 2 ml of 3%glutaraldehyde are subsequently added into the above mixture solution and continue to stir for 5 min.0.4 g of pretreated PET nonwoven fabric is immersed into the suspension,and then exposed to high vacuum for 30 min.The treated PET fabric is heated at 85^oC for 10 min,and then baked at 160^oC for 15 min,and at last dried at 50^oC.The photocatalytic degradation of methyl orange?MO?dye under ultraviolet?UV?irradiation for the titanium dioxide coated PET nonwoven fabric can be obtained by spraying 10%tetrabutyl titanate solution on its surface.?2?PET nonwoven fabric loaded with titanium dioxide and modified with chitosan can not only adsorb heavy metal ions,but also photodegrade MO dye.The optimal conditions to adsorb copper and chromium ions are as follows:When 0.4 g of PET fabric is put into50 ml of 50 mg·l^-1 copper ion solution at pH 5 or chromium ion solution at pH 3,after 12 h of adsorption equilibrium the removal rates for both metal ions are about 75%.The adsorption behaviors are in accord with Langmuir monolayer adsorption model and secondary adsorption dynamics equation.When 0.4 g of titanium dioxide coated and chitosan modified PET fabric is immersed into 50 ml of 10 mg·l^-1 MO solution,the degradation rate of MO dye is around 90%after exposure 5 h of UV irradiation.?3?PET nonwoven fabric modified with chitosan composite gel mixed with microcrystalline cellulose can adsorb heavy metal ions more quickly than that without adding cellulose.Also,the removal rate is improved.When 0.6 g of microcrystalline cellulose is added into 1.5 g of chitosan composite gel,0.3 g of as-prepared PET nonwoven fabric is fabricated and then immersed into 50 ml of 50 mg·l^-1 chromium ions solution at pH 3,the adsorption equilibration time is reduced from 12 h to 10 h compared with that without adding cellulose.The corresponding removal rate is improved from 72%to 87%.The adsorption behavior is conformed to the Langmuir monolayer adsorption model and secondary adsorption dynamics equation.?4?The results of SEM,EDS,XRD,TG and IR confirm that chitosan and/or cellulose are grafted onto PET fibers by means of citric acid.Meanwhile the chitosan composite gel is filled into the interior of PET nonwoven fabric.Anatase titanium dioxide nanoparticles are adhered on the surface of PET fabric.