STUDY OF ADSORPTION ISOTHERMS OF ZINC AND CADMIUM TREATED WASTE WATER

I Nyoman Candra, Prof.Drs.Sri Juari Santosa, M.Eng.Ph.D

2012 | Tesis | S2 Ilmu Kimia

Telah dilakukan penelitian tentang adsorpsi seng dan cadmium menggunakan tanah yang diairi dengan air limbah dan tanah yang tidak diairi dengan air limbah di mana tanah tersebut berada di sebelah utara Braunschweig, Jerman. Untuk mengetahui sifat tanah yang digunakan, tanah tersebut dikarakterisasi terlebih dahulu yang meliputi: kandungan air, pH tanah, persentase pasir, silt dan lempungnya, kandungan karbon organik, dan konsentrasi logamnya. Konsentrasi unsur-unsur yang terukur di dalam fraksi pasir sangat kecil sehingga penelitian ini didasarkan atas kandungan fraksi silt+lempung. Eksperiment kinetika menunjukan bahwa laju adsorpsi seng dan kadmium menggunakan tanah yang diairi dengan air irigasi, termasuk cepat. Pada eksperimen isoterm, data diolah dengan menggunakan persamaan Freundlich dan Langmuir. Nilai kapasitas maksimum adsorpsi seng dan cadmium menggunakan tanah Harvesse berturutturut adalah 83.3 dan 244 mg/kg. Sedangkan dengan menggunakan tanah Volkse Reference, kapasitas maksimum adsorpsi untuk seng dan kadmium adalah: 214 dan 217 mg/kg. Kapasitas maksimum adsorpsi cadmium dengan menggunakan tanah Volkse South adalah 217 mg/kg. Pada eksperimen adsorpsi, peningkatan konsentrasi larutan berakibat pada tidak kontinunya proses pengurangan konsentrasi larutan. Hal ini dapat diakibatkan oleh adanya hidrolisis seng dan kadmium (pengendapan hidroksida). Apabila kita bandingkan antara kapasitas maksimum adsorpsi seng dan kadmium dengan hasil aqua regia digestion, terlihat bahwa konsentrasi seng dan cadmium di dalam tanah masih berada di bawah nilai maksmium yang dapat diadsorp.

An investigation of zinc and cadmium adsorption using two soils from wastewater irrigation fields and a reference soil near Braunschweig was conducted. Prior to use in adsorption experiment, the characterization of soil samples that were: water content, soil pH, percent of sand, silt, and clay fraction, total organic carbon content and metal concentration was investigated. The average sand, silt and clay fractions are: 78.1; 16.9; and 5%, respectively. Whereas, the average measured soil pH for the irrigation field soils is in the range of 5.7 to 5.4. The concentration of measured elements in the sand fraction is almost negligible. Therefore, the silt+clay fraction of soil samples were preferably used in adsorption isotherm. From kinetics experiment, it can be shown that the rates of adsorption of Zn and Cd using the irrigation field soils were quite fast. In the adsorption isotherm experiments, the Langmuir and Freundlich approaches were used. In total soil S∞ of Zn and Cd using soil Harvesse were 83.3 and 244 mg/kg respectively. Those of Zn and Cd for Volkse Reference were 214 and 217 mg/kg respectively. Whereas using Volkse South, this value for Cd was 217 mg/L. Extending the adsorption experiments to higher solution concentrations the development of concentration losses in solution showed no longer a continuous development. This could be due to hydrolysis of Zn and Cd (hydroxide precipitation). A comparison of the aqua regia digestion for Zn and Cd to the corresponding maximum adsorption values showed that the metal concentrations in the soils were clearly below their possible maximum adsorption load.

Kata Kunci : isoterm adsorpsi, karakterisasi sample tanah, fraksi silt+lempung, experimen kinetik.