Effect of Contact Time on the Adsorption of Methylene Blue Onto Almond Shell
Chapter One
AIMS AND OBJECTIVES
The aim of this study was to determine the biosorptive activity of almond shell in removing methylene blue (MB) from aqueous solution.
The objectives of the study are outlined below:
- To study the influence of contact time on the uptake of methylene blue (MB) by almond shell at different initial concentrations.
- Investigate the effect of adsorbent dosage on equilibrium adsorption of methyl blue at different concentrations.
- To investigate the effect of adsorbent dosage on dye removal efficiency of methyl blue onto almond shell at different concentrations.
CHAPTER TWO
MATERIALS AND METHODS
CHAPTERTWO
MATERIALS AND METHOD
MATERIALS
Methylene blue (MB) (C6H18N3SCI), Distilled water, Tap water, almond shell, Sodium hydroxide (0.1m), and Hydrochloric acid (0.1m).
APPARATUS
Volumetric flask, Measuring cylinder, Plastic container, Time piece, Beaker, Sieve, Domestic grinder, Mortar and pestle, Plastic reagent bottle, Conical flask, Spatula, Filter paper, Marker, Hand gloves, Masking tape, Syringe, and Aluminium foil.
INSTRUMENT
Weighing balance, Uv-spectrophotometer, Electronic laboratory oven, Water bath shaker
METHODS:
PREPARATION OF BIOSORBENT (ALMOND SHELL)
The biomaterial (almond shell) used in this study were obtained from Onitsha, where it was generated as primary agricultural waste.
The material collected was extensively washed with tap water and later rinsed with distilled water to remove dirt and other particulate matter that might interact with any sorbed e.g. sand weed etc.
The biomaterial (almond shell) was then dried in the oven at 70 oC and this lasted for 48 hours. It was then grinded with mortar into smaller pieces and finally grinded with a domestic grinder and then sieved with a mesh sieve of 1.0-1.5 mm. The finely divided adsorbent material which was then used for all the concentration and biosorption studies was then stored in a plastic container.
PREPARATION OF STOCK SOLUTION
Methylene blue (MB) with the chemical formular C16H18CIN3S which was used as an adsorbate. 2g of methylene blue was weighed out into a beaker accurately using the electronic weighing balance. The 2g was dissolved with distilled water and poured into 1000ml volumetric flask, and then filled with distilled water to reach up to 1000 ml .It was properly shaken to ensure complete dissolution.
Secondly, dilutions of 50mg/l, 100mg/l, 150mg/l, 200mg/l and 250mg/l were obtained from the STOCK SOLUTION.
These are the WORKING SOLUTIONS; for example, to produce a 25mg/l WORKING SOLUTION from the STOCK SOLUTION. We have M1V1=M2V2
CHAPTER THREE
RESULTS
The calibration results for the absorption of methylene blue are presented in table 3.0. Tables 3.1-3.4 are showing the result including the removal efficiency of methylene blue at different concentrations rangine from 25 mg/L to 250 mg/L. The initial absorbance increases with increasing concentration, thereby giving a straight line plot.
CHAPTER FOUR
DISCUSSION AND CONCLUSION
DISCUSSION
Effect of contact time on initial concentration and percent removal
The adsorption of MB dye at initial concentration of 25 mg/L up to 250 mg/L was studied at different contact time (0 – 120 min) (table 3.1-3.6). Generally, the removal efficiency increased with increasing contact time. The dye adsorption uptake was increased as contact time increased, and reaches equilibrium at 120 minutes (Figure 3.2). The result suggests that, adsorption takes place rapidly at the initial stage on the external surface of the adsorbent followed by a slower internal diffusion process, which may be the rate determining step. In addition, the fast adsorption at the initial stage may be due to the fact that a large number of surface sites are available for adsorption but after a lapse of time, the remaining surface sites are difficult to be occupied. This is because of the repulsion between the solute molecules of the solid and bulk phases, thus, taking long time to reach equilibrium.
The extent of dye removal by activated carbon increased with the increased of contact time. The removal of MB dye by adsorption using activated carbon (almond shell) was found to be rapid at the initial period of contact time and then become slower with the increase of contact time. This is due the strong attractive forces between the dye molecules and the adsorbent. As shown in the Figure 3.3, the capacity uptake of methylene blue at equilibrium on both adsorbents at 25mg/l and 50 mg/l are fairly similar with the capacity uptake of 70-95 %.In general, the results indicate that almond shell were capable to be used in colour removal of methylene blue from the aqueous solution. The results showed that the contact time required to achieve equilibrium was about 120 minutes for adsorption using the shell. This may be due to higher surface area. The results strongly indicate that the activated carbons used in this study are effective in removing methylene blue.
CONCLUSION
Almond shell like other agricultural waste can be used in the treatment process of dyes in wastewater. The adsorption capacity is dependent on contact time. Maximum percentage MB removal (85%) was attained at 120 minutes. The adsorption capacity of almond shell increased with the increase in initial MB concentration. The value of the maximum adsorption capacity, Qt was comparable with the values observed for other adsorbents reported in the earlier studies. These preliminary studies suggest that adsorbent prepared from almond shell can be used effectively for the adsorbent of MB in wastewater.
References
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