Research On Preparation And Properties Of Sensitive Hydrogel To Heavy Metal Ions

The types of sensitive hydrogels were reviewed in this paper.It introduced the preparation methods,including,cross linking polymerization,graft copolymerization and interpenetrating polymer network.The mechanism of its volume phase transition,the responsibility principles of pH-sensitive and thermo-sensitive hydrogels were also especially described.The heavy metal ion is the weak acid and middle acid and easy coordinate to the organic oxygen and the organic nitrogenous.According to this,the topic was carried on the molecular design,proposed the synthesis of acrylic acid sodium low-molecular polymer/acrylic amide copolymer hydrogel.Low-molecular weights poly-acryllic acid soldium was synthesized,the technological conditions of synthesizing was:initiator 0.2%(weight),chain transfer agent4%(weight), temperature80℃,whose molecular was 4370.And then Acrylic acid sodium low-molecular polymer/acrylic amide copolymer hydrogel was synthesized,which was examined by IR and SEM+EDS.In experiment,when heavy metal ion solution density changed,the swelling ratio of acrylic acid sodium low-molecular polymer/acrylic amide copolymer hydrogel was able to have a larger change,but the swelling ratio changes in the light metal Na⁺ solution not to be obvious.Using the orthogonal experiment,pH=3,T=20℃,through determinating the rate of various samples swelling curve in the Zn²⁺,Pb²⁺,Cu²⁺,Na⁺ solution at 0.03mmol/L,obtained the best formula.It could be concluded that the optimal reaction conditions were:acrylic acid sodium :acrylicamide=1:0.3(mol),the neutralization degree of 80%,initiator 0.015%,the amount of crosslinking agent 0.35%,which had a better sensitivity.Sensitive ability was that: Pb²⁺＞Cu²⁺＞Zn²⁺.Besides,the effect of pH and temperature on sensitivity were also studied.It showed that when pH=4,T=30℃,the gel had the best sensitivity. The gel obtained on the condition that acrylic acid sodium:acrylicamide=1:0.5(mol), the neutralization degree of 90%,initiator 0.015%,crosslinking agent 0.20%,which had a Volume phase transition in 0.07mol/L Pb²⁺ solution at pH=3,from swelling to shrink.Through the method of EDTA titration,the hydrogel adsorbing capacity to Pb²⁺ was determined,the effect of pH and temperature on it were also studied.When pH=4,T=30℃, the gel had a best adsorbing capacity.Contrast to the adsorbing capacity of acrylic acid sodium /acrylic amide copolymer hydrogel in 0.07mol/L Pb²⁺ solution,the acrylic acid sodium low-molecular polymer/acrylic amide copolymer hydrogel was better,its maximum adsorbing capacity was 0.0746g/g。In the end,another designed hydrogel sensitive to heavy metal ions was proposed, hydroxyethyl acrylamide hydrogel.Through experiment and contrast its IR to the IR of N-(hydroxymethyl) acrylamide,Hydroxyethyl Acrylamide was synthesized.It showed that the optimal reaction conditions were:methyl acrylate:ethanolamine=1:1.3(mol), temperature70℃,catalyzer1.5%(weight),reaction time 4h.