Sains Malaysiana 34(1): 89-95 (2005)

Pemendakan Logam Karbonat I: Kesan Pencampuran Logam

(Carbonate Metal Precipation I: Effects of Mixed Metals)

Siti Rozaimah Sheikh Abdullah & Lim Sue Ann

Jabatan Kejuruteraan Kimia dan Proses

Fakulti Kejuruteraan

Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor, D.E. Malaysia

ABSTRAK

Objektif kajian ini adalah untuk mengkaji trend kebolehlarutan melawan pH bagi setiap logam secara individu dan juga dalam bentuk campuran dengan logam-logam lain. Melalui kajian ini, julat pH optimum bagi proses perawatan air sisa berlogam melalui pemendakan karbonat dapat ditentukan supaya proses ini dapat dijalankan dengan berkesan dan mtnjimatkan. Proses pemendakan ke atas larutan air sisa sintetik dijalankan dari medium berasid ke medium beralkali dengan menggunakan agen pemendakan natrium karbonat. Alikuot sampel air sisa sintetik diambil pada setiap peningkatan nilai pH dan dituraskan bagi mengetahui kandungan logam dalam hasil turasan sampel yang dianalisa dengan menggunakan alat Spektrometer Serapan Atom (Model FlAS-100, Perkin Elmer, U.S.). Keputusan ujikaji menunjukkan bahawa medium beralkali merupakan medium yang paling sesuai untuk penyingkiran semua logam sama ada secara individu ataupun dalam bentuk campuran . Julat pH optimum untuk proses penyingkiran semua logam dolam sistem air sisa logam bercampur tidak menunjukkan perbezaan yang ketara jika dibandingkan dengan julat pH optimum untuk proses penyingkiran logam secara individu. Namun begitu, julat pH optimum untuk pemendakan kesemua logam dalam air sisa logam bercampur secara serentak adalah 8.0-11.0. Selain itu, proses penyingkiran semua logam dalam sistem logam bercampur didapati bermula pada nilai pH yang lebih rendah berbanding dengan dalam sistem logam individu.

Kata kunci: logam berat, kebolehlarutan ion logam, pemendakan kimia, pemendakan karbonat

ABSTRACT

The objective of this study is to determine the metal solubility trend for each metal either treated individually or in mixed metals. Through this investigation, a range of optimum pH for treating wastewater containing heavy metals by carbonate precipitation can be determined so that the treatment can be performed effectively and economically. The precipitation process for the synthetic wastewater was carried out through acidic to an alkaline medium by using sodium carbonate as the precipitating agent. Aliquots of wastewater sample were taken at every increment of pH value before being filtered out. The residual metal concentrations in the filtered samples were analyzed by using Atomic Absorption Spectrophotometer (MS) (Model FlAS-l00, Perkin Elmer, U.S.). The results showed that the alkaline medium provides the most conducive environment for the removal of every metal regardless of whether the metals were treated individually or mixed metals. It was found that the optimum pH range for the removal of metals in a mixed metal system did not show any significant differences after being compared to the optimum pH range for the removal of metals individually. However, the optimum pH range obtained for the removal of all metals simultaneously in a mixed metal system is 8.0 -10.0. Moreover, metal removal in a mixture system begins at a lower pH value, several units below the pH at which precipitation first becomes apparent in the individual metal system.

Keywords: heavy metals, metal ion solubility, chemical precipitation, carbonate precipitation

RUJUKAN/REFERENCES

Benefield, L.D., Judkins, J.F. & Weand, B.L. 1982. Process chemistry for water and wastewater treatment. New Jersey: Prentice-Hall Inc.

Cerundolo, D.L., Coons, S.E, Gibson, E.D. & Loreti, C.P. 1988. Matrix elements and ligands. Dim. Bodek, 1. (pnyt.), Lyman, WJ. (pnyt.), Reehl, WE (pnyt.) & Rosenblatt, D.H. (pnyt.). Environmental inorganic chemistry: properties, processes and estimation methods, hlm 611-688. New York: Pergamon Press.

Hautala, E., Randall, J. Goodban, A. & Waiss, A. 1977. Calcium carbonate in the removal of iron and lead from dilute waste water. Wat. Res. 11: 243-245.

Jabatan Alam Sekitar. 2002. Peraturan-Peraturan Kualiti Alam Sekeliling (Kumbahan dan Effluen-Effluen Perindustrian) 1979. (atas talian). http://www.jas.sains.my (22 Disember 2003).

Nguyen, N.Y. & Hung, Y.L. 2003. The removal of nickel from wastewater in some nickel plating factories in Hanoi using carbonate precipitation and ferrous co-precipitation. (atas talian). http://www.environmental-center.com/articles/ article920/ removalnickel.pdf  (29 Disember 2003).

Patterson, J.W 1982. Effect of carbonate ion in precipitation treatment of cadmium, copper, lead and zinc. Proceedings of the 36^th Industrial Waste Conference Purdue University, hlm. 579-602.

Patterson, J.W, Scala, J.J. & Allen, H.E. 1977. Heavy metal treatment by carbonate precipitation. Proceedings of the 30^th  Industrial Waste Conference Purdue University, hIm. 32- 1 50.

Rakmi Abd. Rahman, Abu Bakar Mohamad, Salmijah Surif & Hassan Basri. 1994. Treatment of Metal Finishing Wastewater in Sequencing Batch Process. Jurnal Kejuruteraan 6: 3-13.

Sun, J. & Huang, J.C. 2002. Co-removal of hexavalent chromium during copper precipitation. Water Research and Technology 46: 413-419.