|Combating dyes with bottom ash|
As much as we adore batek, we at the same time have to bear its menace. Most textile factories, also some other industries, use dyes and pigment to color their products. Without proper wastewater treatment, the effluents discharged by these factories are no doubt harming the environment. Hazardous dyes such as methylene blue, methyl orange, methyl violet and erythrosine found in the effluents of these factories are a potential harm to mankind and aquatic life. Some of their effects are skin irritation, irritation to mucous membrane, upper respiratory tract and severe headaches.
Researcher Hawaiah Imam Maarof and colleagues of UiTM Pulau Pinang, who conducted experiment to remove the discharge of dyes, awakened us to the more than 9000 types of dyes, color and pigment used by industries. The biggest consumers of these dyes are textile, paper industries, cosmetic, plastic, coffee pulping, pharmaceutical, food processing and electroplating. The discharge of dyes in water resources, even in small amount, can affect aquatic life. The dyes will deplete dissolved oxygen resulting in death of fish.
Now it looks we have to go on a battle with these dyes. There have been many techniques to remove dyes from wastewater. They can be physical, chemical and biological. However, there is no single technique suitable to all types of application. The suitability of wastewater technique will be subject to the characteristics of wastewater, operating cost and size of system. For instance, biological treatment processes have the lowest treatment cost and easy to run but sometimes they are not effective. Other methods such as photochemical degradation, froth flotation, flocculation and membrane filtration can also be used in this case. However, these methods require high technology and are unfortunately expensive. They are also inefficacious and incompetent as their percentage of removal is low, which is not keeping with the cost of maintenance.
But the past 10 years, the world attention has been nailed to a technique called adsorption process. Adsorption process has become proficient as a separation and purification process. It has been proven effective to treat both water and wastewater containing organic pollutants, colour, volatile organic compound and heavy metals.
Activated carbon can be commercially employed as adsorbent. Thus this group of researchers chose coal fired bottom ash, abundantly produced by Malaysian thermal power plants. Hawaiah and colleagues tested the feasibility of bottom ash as an adsorbent. In their experiment, they conducted a batch adsorption study of methylene blue from the aqueous solution. They varied the initial concentration of methylene blue between 20 - 500 mg/L while the adsorbent dosage and the volume of methylene blue solution were fixed at 5 g and 200 mL, respectively. The initial and final concentration of methylene blue was analyzed using the UV-Vis spectrophotometer (Perkin Elmer, Lambda 25) at maximum wavelength of 664 nm. At equilibrium stage, the maximum percentage removal of methylene blue was about 99.3% for initial methylene blue concentration of 20 ppm. It was observed that the uptake (mg of adsorbent/g of dye) of methylene blue increased as the initial concentration of MB increased. The adsorptive characteristic of bottom ash was enhanced by the acid-based activation and In addition, the equilibrium adsorption result was found to be in tandem with Langmuir isotherm. In sum, the bottom ash can be a choice low cost adsorbent to remove dyes in wastewater – good news for our textile industry.
Hawaiah Imam Maarof
Faculty of Chemical Engineering, UiTM Pulau Pinang
|Last Updated on Monday, 17 January 2011 09:10|