A FILM-PORE-SURFACE CONCENTRATION DEPENDENT MODEL FOR ADSORPTION 47 Jurnal Teknologi, 42(F) Jun. 2005: 47–66 © Universiti Teknologi Malaysia 1,2,3&4 Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia. 5 Department of Food Science, Faculty of Food Science and Biotechnology, Universiti Putra Malaysia, 43400 Serdang, Selangor, Malaysia. *Corresponding author A FILM-PORE-SURFACE CONCENTRATION DEPENDENT MODEL FOR ADSORPTION OF DYE ONTO ACTIVATED CARBON THOMAS S. Y. CHOONG 1 *, T. G. CHUAH 2 , AZNI IDRIS 3 , Y. L. LAI 4 & S. Y. QUEK 5 Abstract. Adsorption process has been gaining its popularity as an effective alternative for separation processes. Two fundamental properties that determine the adsorption rate are the adsorption equilibrium and the mass transfer limitation. The adsorption isotherm is obtained from batch studies. The mass transfer coefficients of the batch studies need to be extracted by matching the model with the experimental data. For dye adsorption on activated carbon, concentration dependent surface diffusivity is the most important mass transfer parameter and must be included in the study. The pore diffusivity should also be included to improve the accuracy of the simulation. In this work, a mathematical model for adsorption rate was developed based on the film-pore- concentration dependent surface diffusion (FPCDSD) model. The governing partial differential equations (PDEs) were transformed to ordinary differential equations (ODEs) using orthogonal collocation (OC) method. This set of ODEs was then integrated using the numerical algorithm DIVPAG (IMSL library subroutine), which was based on Gear’s Method. The FPCDSD model is sufficiently general and can be reduced easily to describe other simpler models for liquid adsorption, such as film-concentration dependent surface diffusion (FCDSD) model and film-pore diffusion (FPD) model. The data fitting using the FPD model was unsatisfactory. Both the FPCDSD and the FCDSD model were able to fit the experimental data using a single set of mass transfer parameters. However, the D s ′ values for FCDSD model were found to be about 30% higher compared to that of the FPCDSD model. Keywords: Adsorption, mass transfer coefficients, activated carbon, dye, diffusion model Abstrak. Proses penjerapan terkenal sebagai satu proses pemisahan alternatif yang berkesan. Dua sifat asas yang menentukan kadar penjerapan ialah keseimbangan penjerapan dan had pemindahan jisim. Garis sesuhu penjerapan diperoleh daripada kajian kelompok. Pekali pemindahan jisim bagi kajian kelompok diperoleh menerusi perbandingan antara model dengan data eksperimen. Bagi penjerapan pewarna pada karbon teraktif, kemeresapan permukaan bersandar kepekatan merupakan parameter pemindahan jisim yang paling penting dan mesti dimasukkan ke dalam kajian. Kemeresapan liang juga mesti dimasukkan demi meningkatkan ketepatan penyelakuan. Dalam kajian ini, satu model matematik kadar penjerapan dihasilkan dengan berdasarkan model kemeresapan permukaan bersandar kepekatan-saput-liang (FPCDSD). Persamaan kebezaan separa (PDEs) menakluk ditransformasikan menjadi persamaan kebezaan biasa (ODEs) menggunakan kaedah penempatan bersama ortogon (OC). Seterusnya ODEs dikamilkan menggunakan algoritma berangka DIVPAG (subrutin pustaka IMSL) yang berdasarkan Untitled-6 02/17/2007, 01:36 47 brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by Universiti Teknologi Malaysia Institutional Repository