LIX 84로 함침된 알루미나 비드를 이용한

수용액으로부터의 구리의 선택적 제거

김종성, 이종협

서울대학교 화학공학과

SELECTIVE REMOVAL OF COPPER FROM AQUEOUS SOLUTION USING ALUMINA BEADS  IMPREGNATED WITH LIX 84

Jong Sung Kim and Jongheop Yi

Dept. of Chemical Engineering, Seoul National University

INTRODUCTION

Metal recovery using impregnated ion exchange resins (SIR) from dilute solution has been reported by a number of investigators [1]. SIR uses a solid polymeric matrix as a support which bind chemically active organic molecules. The technique takes advantage of advances made in the development of commercial extractants for metal ion separation hydrometallurgical industries [2].

Inorganic ceramics such as alumna and silica can be used as a solid matrix in stead of polymeric matrix using in SIR, which satisfy the requirements as good supports. The advantage of using porous solid ceramic supports compared to polymeric supports can be summarized as follows: high surface area, good mechanical and heat stability, favorable particle density and relative low cost.

The direct attachment of organic molecules to inorganic surfaces is difficult due to the relative inertness. Solvent extractants can be chemically attached to ceramic surface by proper surface modification method which is adopted by enzyme immobilization [3].

In the study, two different methods-silanization, silanization & bridging were attempted to bind 2-hydroxy-5-nonylacetophenone oxime (LIX 84) at the surface of the pores of alumina beads. The kinetic performances of chemically modified ceramic beads(ICABs) for copper removal from dilute solution were examined. We have also investigated the copper selectivity over other metal ions. Finally, the elution characteristics of copper at low pH were examined.

EXPERIMENTAL

□-alumina beads (□3.6mm, Grace Co) were used as supports. 2-hydroxy- 5-nonylacetophenone oxime in Kerosen (LIX 84, Henkel Co), □-aminopropyl- triethoxy silane ((C2H5O)3Si-(CH2)3-NH2)) and glutaraldehyde (25wt% in water, a. r. grade) were used  without further purification. Stock solutions of Cu(Ⅱ), Cd(Ⅱ) were prepared by dissolving the corresponding salts(a. r. grade) in deionized water.

Two techniques of silanization and silanization-bridging are used for attachment of LIX 84 at □-alumina surface.

For impregnation with LIX 84, vacuum was applied using a vacuum evaporator for 10 minutes before introducing the chelating agents. After all □-alumina beads were fully immersed into the LIX 84, vacuum is applied for 10 minutes. The impregnated ceramic beads were removed, washed with acetone, and dried in air at room temperature. Finally the impregnated beads were washed with deionized water on a rotating shaker for 24 hours to remove the weakly bound organic molecules from the bead surface. ABSO represents the impregnated alumuna beads which are silanized as pretreatment and ABSBO, the impregnated alumina beads which are silanized and successively bridged before impregnation with LIX 84.

The changes of pore structure after chemical modification were examined by BET(Micromeritics, ASAP 2000)

Equilibrium isotherm were obtained by a batch method. 5g of ICABs were placed in flask containing 250ml of 100ppm Cu solution. Cu solution was prepared from CuSO4·5H2O (Junsei, a. r. grade) and deionized water without further purification. The flask were then placed on a shake and rotated gently for 7 days, a time which was expected to be enough for equilibrium to be achieved.

Transient uptake experiments were carried out in column opreration. A pyrex tubev(□ 11mm) was used as a fixed bed reactor in which 5g of ICABs were placed.  The apparatus also comprises a circulation pump (Cole-parmer) and pH meter(DMS, Dp-880M). The flow rate of copper sulfate solution was 40ml/min and 250 ml of feed solution containing 100ppm of Cu(II) and Cd was treated batch-wise. The total operation time was 8 hours. Temperature-regulating bath and condenser cooling system are used to examine the effect of temterature on the removal rate.

Elution ratio of ICABs with various pH conditions were examined using 100ml aqueous sulfuric acid solution of pH 1.0, 1.5 and 2.0. The flasks containing ICABs and the solution was placed on the rotary shaker and equilibrated for 24 hours.

The metal concentration was measured using Inductively Coupled Plasma (Shimadzu, ICPQ-1000). The pH was adjusted by sulfuric acid and sodium hydroxide.

RESULTS AND DISCUSSION

The results of BET analysis show changes of interior structure of the chemically modified alumina beads. Pore volumes and surface areas were reduced considerably by chemical treatment.

Transient data of ABSBO are plotted versus time in Fig. 1 and Fig. 2. For comparison, pure Alumina beads before treatment (AB) and ABSB were tested to check the change of adsorption characteristics. Cu adsorption rates of AB and ABSB are similar to that of ABSBO (Fig. 1) but the Cd adsorption rates of AB and ABSB are much higher than that of ABSBO (Fig. 2). Therefore the selectivity of ABSBO is much higher than that of AB or that of ABSB. The adsorption rate for Cu of three adsorbents per unit weight is similar one another, but the amount of Cu adsorbed per unit surface area is increased by chemical modification by oxime (Fig. 3).

Fig. 4 shows the extraction efficiency of Cu ions from ABSBO with varying pH. The elution rate increases abruptly from pH 2 to pH 1.5 and the rate increases slowly from pH 1.5 to pH 1.0. Below pH 1.5, the concentration factor showed above unity. ICABs after regeneration can be used again for removal of Cu from the dilute solutions.

REFERENCES

[1] Warshawsky, A.,: □Ion Exchange and Solvent Extraction□, Marcel Dekker, New York, 8, 229(1981).

[2] Whewell, R. J., and Hanson,: □Ion Exchange and Solvent Extraction□, Marcel Dekker, New York, 8, 1(1981).

[3] Allen, B. R., Charles, M., and Coughlin, R. W.: Biotech.. and Bioeng., 21,  669(1979).

Fig. 1 Adsorption of Cu(II). Initial        Fig. 2 Adsorption of Cd(II). Initial

Cu(II) concentration=100mg/l,            Cd(II) concentration=100mg/l,

pH=3.8.                                 pH=3.8.

Fig. 3 Adsorption of Cu(II) per unit       Fig. 4 Elution ratio of Cu(II) from

surface area. Initial Cu(II) concentr-       ABSBO. Initial Cu(II) loading=2.28

ation=100mg/l, pH=3.8.                    mg/g, volume of aqueous sulfuric

acid =100ml.