Adsorption Of Methylene Blue Onto Modified Factory Tea Waste: Batch And Fixed Bed Column
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Date
2011-06
Authors
Nasuha, Norhaslinda
Journal Title
Journal ISSN
Volume Title
Publisher
Universiti Sains Malaysia
Abstract
The aim of this work was to investigate the feasibility of chemically modified agricultural waste, namely factory tea waste (R-TW) for adsorption of methylene blue (MB) from aqueous solutions. The results revealed that modification of R-TW with sodium hydroxide (NaOH) and potassium hydroxide (KOH) which named NaOH-TW and KOH-TW respectively give the highest efficiencies for MB adsorption compared with other modification methods. R-TW, KOH-TW and NaOH-TW were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and nitrogen adsorption/desorption isotherm analyses. The effects of MB initial concentration (50–500 mg/L), contact time, temperature (30, 40 and 50 ºC) and solution pH (3–12), on MB adsorption were investigated in batch process. The results show the MB adsorption uptakes increased with increasing initial concentration and contact time. The highest removal efficiency of MB was at pH 7–10 for R-TW, KOH-TW and NaOH-TW. Adsorption isotherm of MB on all adsorbents was best fitted by Langmuir isotherm model. The maximum monolayer for adsorption capacity MB followed the trend R-TW < KOH-TW < NaOH-TW. The pseudo-second-order kinetic model described well the experimental data of MB adsorption on all adsorbents. The adsorption process for all adsorbents represented physisorption mechanism since activation energy was lower than 40 kJ/mol. A series of experiments were conducted to measure the breakthrough curves for adsorption of MB on R-TW, KOH-TW and NaOH-TW in fixed bed
column under different operating conditions including initial concentration (50, 100 and 200 mg/L), bed flow rate (10, 20 and 30 mL/min) and bed height (20, 40 and 60 mm). It was found that the amount of MB adsorbed, (mg/g) increased with increasing initial concentration and flow rate and decreased with increasing height of column bed. A Thomas model was the best model to predict the breakthrough characteristics.
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Keywords
Feasibility of chemically modified agricultural waste , for adsorption of methylene blue