ADSORPTION OF CONGO RED DYE ONTO COCONUT SHELL BASED NaOH ACTIVATED CARBON: KINETICS, THERMODYNAMICS AND OPTIMISATION STUDIES

摘要

Coconut Shell (CS) was carbonised, activated with NaOH and used to adsorb Congo Red (CR) dye from its aqueous solution.Proximate and ultimate analyses, Fourier Transform Infra-red (FTIR) and Scanning Electron Microscope (SEM) were used tocharacterize both the raw and the Coconut Shell Activated Carbon (CSAC) while UV spectrophotometer was used to monitorthe CR dye concentration. Batch adsorption experiments were carried out using 100 ml each of 50 mg/l to 250 mg/l CR dyesolution at different contact times, and temperature. To establish optimum adsorption conditions, Central Composite Design(CCD) in Response Surface Methodology (RSM) was employed using the initial dye concentration, contact time andtemperature as variables at a fixed pH of 3 and 0.2 g/100ml of adsorbent. Adsorption capacity of 122.00 mg/g was obtainedwith CR concentration, contact time and temperature of 250 mg/l, 180 min and 30oC, respectively. Pseudo first order kineticmodel best fitted the experiment. The coefficients of determination of Langmuir, Freundlich and Temkin isotherms were 0.978,0.974 and 0.863, respectively, with Langmuir isotherm giving a better fit for the adsorption. The maximum monolayer adsorptioncapacity from Langmuir isotherm was 121.56 mg/g at pH 3 and a temperature of 30oC.