Dye is a visible pollution.Even a slight colouration of water sources could make them unacceptable to consumers though it may not be toxic to the same degree.The source of such pollution lies in the rapid increase in the use of synthetic dyes.More than 10,000 chemically and dyes chemically diï¬€erent dyes are being manufactured. The world dye stuï¬€ and dye intermediates production is estimated to be around 7 x 108 kg per annum (Fu and Viraraghavan, 2001; Toh et al., 2003). These are mainly consumed in textiles, tanneries, pharmaceuticals, packed food industries,pulp and paper,paint and electroplating industries. The release of dyes into waters by industries is undesirable and causes serious environmental problems. It contains various organic compounds and toxic substances which are hazardous and harmful to aquatic organisms. The colored waste water in the receiving streams reduces the light penetration through the water's surface and therefore, reduces photosynthesis activity (Weisburger, 2002).
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There are several techniques of removal of dyes from waste water. Some of them are, by flotation, precipitation,oxidation,filtration,coagulation,ozonation,supported liquid membrane, and also biological process.Meanwhile, a new and more environmental friendly method, the biosorption process is proven to be a promising process to remove dyes from effluent. It is stated by D.J Ju et al. in his research on 2006, biosorption is also known as the uptake or accumulation of chemicals by biomass. This process is similar to adsorbent process which it is cost-effective, easy to operate, simply designed and insensitivity to toxic substances. In this study, Methylene Blue (MB), known as strong adsorptions into solid, will be used as the biosorbate. MB is an important basic dye widely used for printing cotton and tannin, and dyeing leather. Even though it is not strongly hazardous, MB can cause harmful effects to human and other living organisms. Too much exposed of MB can cause eye burns and causes irritation to the skin.
The expose of dyes into environment by various industries has been aesthetically undesirable and too much of it will eventually cause serious environmental effect, aquatic or non-aquatic. This is due to its properties which are mostly toxic, mutagenic, and carcinogenic. Dyes are causing pollution to the environment, for example, dyes adsorb and reflect sunlight from entering water and thus interfere the aquatic ecosystem. Dyes when release can have acute and or chronic effects. It is evidently, therefore, investigating the removal of dyes is significant environmental, technical, and commercially important.
Rhizopus oligosporusÂ is a fungus of the family Mucoraceae that is a widely usedÂ starter cultureÂ for the home production ofÂ tempeh. The spores produce fluffy, whiteÂ mycelia, binding the beans together to create an edible "cake" of partly fermented soybeans.In this fermention industries Rhizopus oligopsporus also comes out as a waste product which make it suitable for investigations of biosorbtion capacity. Therefore, in making this fungi a better use, it is proposed as a biosorbent to remove dyes.It is also renewable,so the costs of biomass raw materials are extremely low.
To study the effect of biosorbent dosage and the pH of dye solution on the percentage dye removal
To compare the effect of addition of activated carbon together with the biosorbent dosage.
4.1) RATIONAL OF THE RESEARCH
Pollution caused by dyes had affected the society with serious environmental effect and health problems to human body. It is evident; therefore, removal of dyes from aqueous solutions is important. Problems caused by the waste of food processind-derived rhizopus oligoporous can be solved by making use of the biomass as a biosorbent to remove dyes. Today activated carbon is commonly used for adsorption in many treatment plants.But the producing costs for activated carbon is very high,there is a need of an alternative material is more cost efficient.Biosorption process is an effective alternative method to replace conventional method, which is high cost and more complicated compared to biosorption.
4.2) CURRENT RESEARCH
4.2.1) Kumari and Abraham, 2006
Kumari and Abraham (2006) made a study on the biosorption behavior of nonviable biomass of four fungi (R. nigricans, R. arrhizus, A. niger and A. japonica) and one yeast (S. cerevisiae) treating five different reactive dyes. These organisms are all produced as byproducts in fermentation industries and other studies show that they are good biosorbents of heavy metals and radioactive compounds. The result of Kumari and Abraham's study shows that most of these organisms also are good biosorbents of reactive dyes. Only A. japonica shows quite low values, around 4-20% adsorption, for the five dyes tested. Aspergillus niger adsorbed between 58-68%. S. cerevisiae and R. nigricans was the best adsorbents (55-91%) and was for some dyes comparable to the values given by adsorption
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with activated carbon. These two organisms were then studied further.The pH of the dye solutions was around 5.9-6.1, but there was also an experiment done at pH 10. At pH 6 the adsorption was most efficient, at pH 10 S. cerevisiae didn't adsorb any dye at all while R. nigricans only could adsorb smaller amounts of reactive green and reactive blue.
A study made by Khalaf (2008) focused on textile wastewater treatment by non-viable biomass of Aspergillus niger and the alga Spirogyra. The dye solution contained the commercial Synazol reactive dye, a mixture solution with one red and one yellow dye. The biosorption experiments were performed at different initial pH (1-8), different temperature (15-45 °C) and different biomass loading (4-12g/L). The A.niger and Spirogyra biomass was inactivated by either gamma radiation or autoclaving. Autoclaving resulted in the highest biosorption values. Another study made by Fu and Viraraghavan (2000 and 2002) even showed that autoclaved biomass of A. niger even had higher biosorption capacity compared to living biomass.The surface characteristics of the biomass are changed in a way that improves the dye biosorption capacity. A possible explanation to that is that the autoclaving disrupts the biomass structure and then exposes the adsorption sites even more.The result of the study showed that the highest biosorption values were obtained at pH 3 and the lowest values occurred around pH 6-8.The optimal temperature and biomass loading for the biosorption was found to be at 30 °C respectively at 8 g/L.
4.3) ADVANTAGES AND IMPORTANT OF THIS RESEARCH
Generally, dyes are difficult to biodegrade(Fu and Viraraghavan,2000).Application of biological processes to treat coloured wastewater is yet to be fully established.Between treatment technologies,adsorption is rapidly gaining relevent as a method of treating wastewater.Activated carbon is the most effective and always used as adsorbent(El-Guendi,1991).However,its high cost has prevented its application,so it is necessary to search for an alternative low-cost adsorbent which can be the replacement for activated carbon.Since 1980s,biosorption has been continuosly studied for wastewater treatment,so it could be an alternative to be the replacement for activated carbon.
Biosorption ,if compared to the other available technologies such as precipitation,ion exchange,reverse-osmosis and adsorption,gives comparable performance at a very low cost.Apart from cost effectiveness and competitive performance,other advantages are possible regeneration at low cost,availability of known process equipment,sludge free operation and recovery of the sorbate(Volesky,1999).The use of dead biomass is better than live biomass because toxic or pollutants from nature cannot effect on the sorption process.Besides,there is no requirement for either having any nutrients or maintaning a growth enviroment.
Other than that,fungal biomass seems to be good material because it can produced economically using simple fermentation and economical growth media.Furthemore,fungal biomass is also available as by-product or waste material from various industrial processes(Fu and Viraraghavan,2000).It is easily and economically available anywhere,especially in locations with hot and humid such as Malaysia.
4.4) SCOPE OF THE STUDY
This study investigates the biosorption abilities of inactive rhizopus oligosporus for the removal of Methylene Blue (MB) dye from aqueous solutions. There are two parameters to be studied which are the characteristic and effects of biosorbent dosage with or without additional of activated carbon and solution pH.
Biosorption is a property of certain types of inactive, dead, microbial biomass to bind and concentrate heavy metals - or other types of molecules or ions - from even very dilute aqueous solution. Biomass exhibits this property, acting just as chemical substance, as an ion exchanger of biological origin. It is particularly the cell wall structure of certain algae, fungi and bacteria which was found responsible for this phenomenon. In similar meaning stated by D.J. Ju et al in his research, the uptake or accumulation of chemicals by biomass is known as biosorption.
There are a lot of efforts were made in many studies for the removal of dyes from either aqueous solutions or wastewaters. This includes the use of metal hydroxides, clays, sunflower stalks, hardwood, fertilizers and steel wastes.The biosorbent used in the study were prepared from autoclaving and driying rhizhopus oligosporus(biomass).The dye solution will be treated with inactivated rhizopus oligosporus. This is because,if the cells of the fungi are active they are easily affected by toxic compounds and chemicals in the waste water and they may then pollute the enviroment by releasing toxins.Another problem when dealing with active biomass is that it could not be stored at room temperature for long time periods before it may purtefy.When the biomass is dead and dried it could be stored and transported easier.Earlier studies also showed that autoclaved biomass actually has higher biosorption capacity than living biomass(Fu and Viraraghan,2000 and 2002).These facts are the reasons why inactivated biomass by autoclaving is chosen for this experiment.
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Methylene blue (MB,chemical formula: C16H18N3SCl; FW:320â€‰gâ€‰molâˆ’1,Â ðœ†max=Â 662â€‰nm and class: thiazine.MB is not regarded as acutely toxic, but it can have various harmful effects. On inhalation, it can give rise to short periods of rapid or difficult breathing, while by ingestion through the mouth it produces a burning sensation and may cause nausea, vomiting, diarrhea, and gastritis.MB is used as model dye for this reasons:
MB is one of the commonly used commercial dye
MB is well known for its adsorption characteristics to the solid
MB compared to the other dyes.have high briliance and colour intensity,resulting in high visible colour,even at very low dye concentration(Fu and Viraraghavan,2000)
The experiment could be divided into two different parts.The first part is the biosorbent preparation and the second part is the biosorption experiments.
5.1) Biosorbent preparation
The solid agar, Potato Dextrose Agar (PDA), is prepared by mixing a prepared powder with de-ionized water. The composition of the agar is 5.0g/L potato, 20.0g/L dextrose, 13.0g/L agar and 0.1g/L chloramphenicol. After preparation the PDA is autoclaved at 121°C for 30 minutes. The petri dish containing the PDA are then laid down at room temperature until the medium is turned into solid mass. When it is solid the tubes are incubated for 1 day. After incubation one could be excluded that other biomass is growing at the agar.
The rhizopus oligoporus grown on PDA is stored in a fridge at 4°C. By inoculating the cultures further onto fresh PDA the biomass is deactivated,After inoculation the dish are incubated for at least 5 days.
After the incubation the biosorbent is inactivated by being autoclaved at 121°C for 30 minutes. The mixture is then filtered to get rid of the supernatant and to get only biomass. After filtration the biosorbent is dried in an oven at 80°C for 24 hours. When the biomass is dry it is powdered and it is ready for the biosorption experiment.
5.2) Biosorption experiment
Two different biosorption experiments is performed according to two different parameters; biosorbent dosage and pH. Each experiment will be done in different intervals and in duplicate samples.
The dye solutions used is prepared by mixing the methylene blue stock solution with a water solution at a NaCl concentration off 30g/L. The concentration of the methylene blue stock solution is 1g/L.
The biosorption will take place in an incubator at temperature 30+/-1 °C, a shaking of 150 rpm and during 16 hours.
After the biosorption the samples will be filtrated to get the supernatants.
The absorbance of that solution is measured by a Vis/UV Spectrophotometer and the absorbance units are then converted into concentration units by using a standard curve.
5.2.1) Biosorption dosage
The biosorption experiments with different biosorbent dosage is performed at natural pH and an initial dye concentration of 50mg/L. The dye solution is prepared by taking 50ml of the stock solution and adding de-ionized water until the volume is 1 liter. Seven different biosorbent dosages is used; 0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6g. The biosorbent is weighted and put into a test tube. Then 50 ml of the dye solution is added to every test tube.
Now the biosorption experiments will be performed at different pH. As in the experiments above the initial dye concentration will be 50mg/L. The proper biosorbent dosage to use in this experiment is got in the previous experiment. Six different initial pH will be tested; 2, 4, 6,8, 10 and 12. The pH of the dye solutions is prepared by adding 1M HCl or NaOH solutions.
The standard curve is used to convert the absorbance values into concentrations. Then the decolorization and amount of biosorbed dye per unit Rhizopus oligoporus, the biosorption capacity (Qe), could be calculated.C0 is the dye concentration in a blank sample with no biosorbent.C0 could be defined as the initial dye concentration but then it is not taken into account that the dye could also be taken up by for example the filter paper during the filtration or lost during some other process. When C0 is defined as the blank concentration we are only taking the biosorption into account when calculating the decolorization and biosorption capacity.Ce is the concentration at equilibrium after the biosorption.
Table 1: The absorbance at different known concentrations of methyelene blue dye solutions.
The standard curve of methelyene blue dye solution