Modification Of Natural Polymer And Its Application In Wastewater Treatment Of Heavy Metal Ions

In recent years, wastewater containing heavy metal ions has attached more andmore attentions, and many kinds of adsorbents have been used in wastewatercontaining heavy metal ions treatment. Natural polymer and its derivatives, whichhave a wide range of advantages, such as from large resources, cheap,biodegradability, innocuous, simple preparation and so on, are easily used to preparedpolymer adsorbent with different textures and different purposes, due to its structurediversity and active group diversity. In this thesis, the effective andenvironmentally-friendly adsorbents were prepared using bentonite, cellulose,polyacrylic acid, and were applied to remove heavy metal ions from wastewater. Ithas a very important practical significance.Firstly, modified methods of bentonite, and bentonite's derivatives applied inwastewater containing heavy metal ions treatment were reviewed. Modified methodsof cellulose, cellulose and its modified products in wastewater containing heavy metalions treatment were reviewed. The limits of bentonite and cellulose in application ofthe environment were also pointed out.Secondly, the PAA/Bent were prepared using acrylic acid and sulfuric acidbentonite. The optimum conditions for preparation of PAA/Bent were given based onthe removal rates of Pb²⁺. Furthmore, the obtained PAA/Bent was characterized byFT-IR spectra,TGA/DTA , XRD and SEM.Thirdly, we have investigated the adsorption ability of PAA/Bent towards Heavymetal ions (Pb²⁺, Cu²⁺) and COD adsorption properties of mining waste water. (l)We have treated the Pb²⁺ Containing simulated wastewater using PAA/Bent asadsorbent. The optimal condition is as following: [Pb²⁺] 500 mg/l, PAA/Bent: 1 g/L,pH: 5.0, oscillating 60 min in 20 oC. Under the condition, the Removal rate reached to99.9%. The effiuent meet the class I of National Intergated Wastewater DischargeStandard (GB8978-1996). Adsorption dynamics consistent with pseudo-second orderkinetic model; isotherm model can meet the Langmuir isotherm. (2) We have treated the Cu²⁺ Containing simulated wastewater using PAA/Bent as adsorbent. The optimalcondition is as following: [Cu²⁺] 200 mg/l, PAA/Bent: 1 g/L, pH: 6.0, oscillating 60min in 20 oC. Under the condition, the Removal rate reached to 97.8%. Adsorptiondynamics consistent with pseudo-second order kinetic model; isotherm model canmeet the Langmuir isotherm. (3) PAA/Bent was also used to treat the mining wastewater of COD. The optimal condition is as following: mine drainage solution 100 mL,PAA/Bent: 0.25 g/L, pH: 5.0, oscillating 2 min in 20 oC. Under the condition, theRemoval rate reached to 78.9%.Fourthly, The wheat straw/poly(acrylic acid) (WSC/PAA) composite wasprepared by wheat straw and graft acrylic copolymer. FT-IR spectroscopy, scanningelectronmicroscopy (SEM) and thermogravimetric analysis (TGA) techniques areused to characterize it. We have treated the Pb²⁺ Containing simulated wastewaterusing WSC/PAA as adsorbent. The optimal condition is as following: [Pb²⁺] 600 mg/l,PAA/Bent: 1 g/L, pH: 5.0, oscillating 60 min in 20 oC. Under the condition, theRemoval rate reached to 99.8%. The effiuent meet the class I of National Intergatedwastewater Discharge Standard(GB8978-1996). Adsorption dynamics consistent withpseudo-second order kinetic model; isotherm model can meet the Langmuir isotherm.