Preparation Of Amino Starch/Attapulgite Composites And The Adsorption Of Heavy Metals

The treat of heavy metals has been taken more and more attention,with the serious water pollution problem caused by heavy metals in recent years.Among the different kinds of treatments,the adsorption approach has been studied by many researchers for its high efficiency,easy handling,low cost and the availability of different adsorbents.The raw materials of the traditional adsorbents are usually derived from petroleum.Although these adsorbents has excellent adsorption properties,they are difficult to degrade in the natural environment,likely to cause secondary pollution.Otherwise,the raw materials is kind of wasting resurces,diffcult to recycle,and contrary to the current trend of"green chemistry".Based on previous studies,this paper has uesd the starch and attapulgite as the raw materials which exhibits many advantages,such as wide variety of sources,environmentally friendly,low price and easy to modify.Acrylic acid and polyvinyl alcohol are compounded with the starch and attapulgite respectively to prepare two inorganic/organic composite adsorbent,which both cotain a large number of functional groups and special structure.And the structure,performance and adsorption characteristics have been investigated,the main contents include:?1?The amino starch-graft-attapulgite/acrylic acid composites?AAP?were synthesized by the inverse suspension polymerization.The results of the test of adsorption towards copper ions showed that,when the attapulgite were modified by coupling agent KH792,the neutralize degree of AA was 60%,the mass ratio:ASt/AA=1:4,792-ATP/AA=1:8,the content of Span80,crosslinking agent and initiator were 3%,2%and 1.5%respectively,the O/W=3:1,the adsorption capacity of composites was the highest.After the graft,a layer of inorganic/organic crosslinked network structure has been covered on the surface of the amino starch.The AAP also possessed a good thermal stability.?2?AAP has the characteristics of rapid adsorption,which only need 45min can reach the equilibrium.AAP showed a best adsorption effect when the pH of solution was 4.The adsorption isotherms,thermodynamics,and kinetics study of AAP found that,the Langmuir equation and the pseudo second equation was more suitable to explain the absorption procedure of Cu²⁺onto the AAP.In the adsorption process of AAP,the chemisorption played a leading role.?3?A spherical amino starch/attapulgite/Polyvinyl alcohol?PAA?composite was prepared,which possesed rich macroreticular structure,good thermal stability and chemical stability also a good adsorption ability to heavy metals.Utilizd the triethylenetetramine modified crosslinked starch with dosage of 4%,and dosage of792-ATP,CaCO₃,SA were 4%,10%,2%,the PAA showed a best adsorption ability.?4?When the solution pH was 5,the equilibrium adsorption capacity of PAA for Cu²⁺,Pb²⁺was the greatest.the Langmuir isotherm equation and the pseudo second equation were more suitable to explain the absorption procedure of PAA.PAA showed a high desroption rate on the Cu²⁺,Pb²⁺with the 0.05mol/L HNO₃ as desroption solution.After five absorption-desroption cycle,the adsorption capacity of PAA for Cu²⁺,Pb²⁺still remained the 85.1%,84.7%of the first time,respectively.