title: Adsorption kinetics of maxilon yellow 4GL and maxilon red GRL dyes on kaolinite.
abstract: Kaolinite, a low-costly material, is the most abundant phyllosilicate mineral in highly weathered soils. In this work, the adsorption kinetics of maxilon yellow 4GL (MY 4GL) and maxilon red GRL (MR GRL) dyes on kaolinite from aqueous solutions was investigated using the parameters such as contact time, stirring speed, initial dye concentration, initial pH, ionic strength, acid-activation, calcination and solution temperature. The equilibrium time was 150 min for both dyes. The results showed that alkaline pH was favorable for the adsorption of MY 4GL and MR GRL dyes and physisorption seemed to play a major role in the adsorption process. It was found that the rate of adsorption decreases with increasing temperature and the process is exothermic. The adsorption kinetics followed the pseudo-second-order equation for both dyes investigated in this work with the k(2) values lying in the region of 1.79 x 10(4) to 107.87 x 10(4)g/mol min for MY 4GL and 3.44 x 10(4) to 72.09 x 10(4)g/mol min for MR GRL. The diffusion coefficient values calculated for the dyes were in the range of 3.76 x 10(-9) to 62.50 x 10(-9)cm(2)/s for MY 4GL and 1.98 x 10(-9) to 44.00 x 10(-9)cm(2)/s for MR GRL, and are compatible with other studies reported in the literature. The thermodynamic activation parameters such as the enthalpy, entropy and free energy were determined. The obtained results confirmed the applicability of this clay as an efficient adsorbent for cationic dyes.
authors.affiliation: Department of Chemistry, Faculty of Science and Literature, Balikesir University, Balikesir, Turkey. mdogan@balikesir.edu.tr
authors.forename: Mehmet
authors.initials: M
authors.lastname: Doğan
authors.forename: M Hamdi
authors.initials: MH
authors.lastname: Karaoğlu
authors.forename: Mahir
authors.initials: M
authors.lastname: Alkan
mesh_terms: D000327:Adsorption; D000814:Aniline Compounds / Q000302:isolation & purification*; D001391:Azo Compounds / Q000302:isolation & purification*; D002412:Cations; D004396:Coloring Agents / Q000302:isolation & purification*; D006835:Hydrazones / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D007616:Kaolin / Q000737:chemistry*; D007700:Kinetics; D009994:Osmolar Concentration; D011726:Pyridinium Compounds / Q000302:isolation & purification*; D013696:Temperature; D013816:Thermodynamics; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods
chemical_list: D000814:Aniline Compounds; D001391:Azo Compounds; D002412:Cations; D004396:Coloring Agents; D006835:Hydrazones; D011726:Pyridinium Compounds; D014874:Water Pollutants, Chemical; C541781:maxilon red GRL; C541780:maxilon yellow 4GL; D007616:Kaolin