Preparation Of Modiifed Solvent Impregnated Resins Containing Sec-octylphenoxy Acetic Acid And Their Adsorption Properties For Indium (Ⅲ)

The demand for indium has increased in recent years because of its extensively beingused in the manufacture of liquid crystal displays and semiconductors. It is not mined foritself, and it has to be recovered as a byproduct from other metallurgical processes or fromsecondary raw materials. Solvent extraction or ion exchange process has been employed inthe recovery of indium. However, the main drawback of solvent extraction process isattributed to the loss of extractant into aqueous solution, which may cause environmentalhazard and economic limitation. Ion exchange process is simpler, but the low selectivity andslow adsorption and desorption rates for metal ions are its main problems.Solvent impregnated resins(SIRs) technique combines the advantageous features of bothsolvent extraction and ion exchange technique, and SIRs containing organophosphorusextractants have been used in the adsorption and separation of indium. But the maindisadvantage of the extractant materials is toxic and less adsorption capacity. At the same time,the main disadvantage of SIRs technique is its low stability because of the leakage of theextractant from polymeric support and long adsorption time.Sec-octylphenoxy acetic acid (CA-12) as a novel carboxylic acid is non-toxic and highextraction capacity. In this study, it was used as extractant, and styrene-divinylbenzenecopolymer (HZ818) was used as support in preparing SIRs. HZ818was firstly modified afternitration of the benzene rings present in its structure, and then CA-12was impregnated tomodified support by dry technique. Hence the first modified SIRs (NSIRs) were prepared.The second modified SIRs were prepared as follows. Traditional SIRs were firstlyprepared by impregnation of CA-12on HZ818by dry technique, and then were coated withPVA–boric acid cross-linking method to enhance their stability. The coated SIRs(CSIRs) wereformed.Three kinds of adsorption materials (SIRs, MSIRs, CSIRs) were systematicallycharacterized by FTIR analysis, scanning electron microscopy and thermogravimetric analysis,and their adsorption behaviors for indium (III) in hydrochloric acid solution were investigatedby batch and dynamic method.It was shown that optimal pH for indium(III) was found to be3.0with three kinds ofresins. And the adsorption capacities for indium(III) were52.3mg/g,57.6mg/g and60.7mg/g with SIRs, NSIRs and CSIRs at35℃, respectively. The adsorption isotherms were found tofollow Langmuir isotherms at different temperatures, and the maximum adsorption capacitiesincreased with increasing temperature. The adsorption processes of indium (III) with all ofresins were endothermic. Kinetics data indicated that the adsorption processes of indium (III)were in a good agreement with the pseudo second-order rate equation, and governed by thefilm diffusion. MSIRs exhibited highest adsorption rate among three kinds of resins. Both ofNSIRs and CSIRs sustained adsorptivity well through several adsorption-elution cyclescomparing with SIRs. In addition, indium(Ⅲ) could be adsorbed selectively from simulationsolution containing Zn(Ⅱ), Cu(Ⅱ), Cd(Ⅱ) and In(Ⅲ) with SIRs and CSIRs at pH3.