The use of cheap and eco-friendly adsorbents has been studied as an alternative substitution of activated carbon for the removal dyes from wastewater. Activated carbon is the most widely used adsorbent because it has excellent adsorption efficiency of the organic compound.
But, commercially available activated carbon is very expensive. Presently there is growing interest in using inexpensive potential materials for adsorption of dyes.
This work focus on the utilization of agricultural waste like rice husk, bagasse, tree fern, and hemp stems and lingzhi mushroom for the removal of dye from aqueous solutions. Simple structural modification of rice husk, bagasse, and flex fibre increase absorption capacity of these materials which were used as the adsorbent for the removal of dye.
The result indicates that modified rice husk could be employed as low-cost alternatives to commercial activated carbon in wastewater treatment for the removal of basic dyes. A batch sorption system using tree fern as biosorbent was investigated to remove basic dye from aqueous solutions. Use of coconut shell was proved to be a simple adsorbent for removing direct dye from textile waste water.
Use of coconut shell was proved to be a simple adsorbent for removing direct dye from textile wastewater. Similarly, caustic treated bagasse and hemp stems were found to be efficient adsorbent for reactive dyes. Treatment of textile dye waste was carried in a batch reactor using lingzhi mushroom.
The characteristics of textile dye wastewater were studied. At the optimized conditions, the maximum decolourization and COD reduction were found. The adsorption system variable study includes a type of sorbent, nature of dye, pH, temperature, and results revealed the potential of, an agricultural product, as a low-cost sorbent.
Dyes are basically natural or synthetic, organic compounds that can connect themselves to surfaces or fabrics to provide bright and lasting colour. They are applied in various industries such as leather, textile, paper, rubber, cosmetics, plastic, pharmaceuticals, and food industries.
Most of them are complex organic molecules and are resistant to many things such as the action of detergent. Coloured dye wastewater is regarded as a direct result of the production of the dye and also as consequence of its use in textile and related industries.
The conventional waste water treatment, rely on aerobic biodegradation have low removal efficiency for various dyes. Due to low biodegradation of dye, the conventional biological treatment process is not very effective in treating dye waste water. However, these processes are very expensive and cannot effectively be used to treat the wide range of dyes waste.
It is difficult to separate industrial growth from environmental pollution but it can be minimized through cost effective approaches of pollution abatement. To reach the full objectives of zero pollution, adoption of alternative technologies which suit the solution of row capital availability, minimum man power and limited energy consumption are necessary.
Adsorption through agricultural products such as rice husk, sugarcane bagasse, soybean hulls, saw dust, coconut shells, groundnut shell, apple-waste, fly-ash etc., has been demonstrated to be a useful alternative to the conventional treatment systems for the removal of toxic metals such as dyes/colour, chromium (Cr), mercury (Hg), copper (Cu), nickel (Ni), etc., from aqueous solution. In the present study, it was aimed to carry out experiments using low-cost material like bagasse, fly ash from the combined waste water.
The adsorption process is one of the effective methods for removing dyes from waste effluent.
The process of adsorption has an edge over the other methods due to its sludge free clean operation and completely removed dyes, even from the diluted solution.
Activated carbon (powdered or granular) is the most widely used adsorbents because it has excellent adsorption efficiency of the organic compound. But, commercially available activated carbon is very expensive. Furthermore, regeneration using solution produced small additional effluent while generation by refractory technique result in a 10-15% loss of absorbents and its uptake capacity.
Adsorption currently appears to offer the best potential for overall treatment and it is found to be an efficient and economically cheap process for removing dyes using various adsorbents. Activated carbon is known as to be highly effective adsorbent: however, it has higher operating costs.
Therefore, in recent years, considerable attention has been devoted to the study of different types of low-cost materials.Where examples are the zeolite, coconut husk. Agricultural by-products are considered as low-value products.
The effluent containing dyes are highly coloured, resulting in major environmental problems. Physical methods, main adsorption on various supports, as the most frequently used. However, adsorption is one of the promising methods to remove the dye pollutants from the aqueous system completely.
It was, therefore, thought adsorbents for the removal of dye from textile effluents. In the present investigation, attempts have been made to explore for the removal of dye with activated carbon prepared from rice husk.
Tree fern is naturally and commercially available in Taiwan. This variety of tree fern is generally horticultural purposes because of its character of sorbability to retain water and manure for plants. Tree fern, an agricultural by-product, has been currently investigated to remove heavy metals from aqueous solutions.
Many microorganisms, including bacteria, fungi, and actinomycetes, have been reported for their ability to decolourise dyes. Among these micro organisms, white rot fungi are the most intensively studied dye decolorizing microbes.
These fungi produce large quantities of extracellular enzymes that help to remove dyes from industrial effluent. In the study, a white rot fungal stain, Ganoderma lucidum, was examined for its ability to decolourise the textile dye in industrial wastewater.
ROLE OF DIFFERENT AGRICULTURAL WASTE AS AN ADSORBENT
Over the last few years, sizeable research investigations have been undertaken by various researchers for wastewater treatment using adsorption process. The adsorption process is utilized as a stage of an integrated chemical-physical-biological process for the treatment of wastewater, or simultaneously with a biological process.
Adsorption is a surface phenomenon in which a multi-components fluid (gas or liquid) mixture is attached to the surface of a solid adsorbent to form attachments via the physical or chemical bond. The substance that providing the solid surface is termed as adsorbent while material removed from the liquid phase is known as the adsorbate.
Tiny chemical particles suspended in another phase of matter, meaning in the air as a gas or in water as a liquid, are considered as contaminants. These contaminants can be separated from those phases through adsorption process that bonded onto the solid phase.
Activated carbons treated from low-cost rice husk by sulphuric acid and zinc chloride activation were used as the as an adsorbent for the removal of methylene blue, a basic dye from aq. Solution.
The raw tree fern was dried in an oven at 1000C for 24 h. and screened. The dye sorption capacity of tree fern increased as the sorbent particle size decreased maximum. Saturated monolayer sorption capacity of tree fern for Basic Red 13 408 mg/g.
The coarse hemp was treated with 5% NaOH at boiling temperature in order to remove lignin, Pectin, and hemicelluloses. The treated material washed with water to remove excess of caustic and it was dried in sunlight for 48 hrs.
The raw bagasse treated with 5% NaOH solution in the ratio 1:5 and heated at boiling temperature for 1hrs. The material thus obtained was washed with water to remove excess amount of NaOH and dried in sunlight to remove moisture. There is maximum adsorption of Novacron Brill Red FN 3GL on modified bagasse, modified Hemp as compared to activated carbon during first 20 minutes.
The waste material coconut shells are were washed with tap water to remove soil and dust, sprayed with distilled water, and dried to constant weight at 1050C.Direct dye Cango red, which was present in wastewater was removed in5 hrs.
The raw material of mushroom collect and it is well preserved in the laboratory. The strain is maintained on solid medium at 40C. The media composition and process conditions were : Agar 20 g/l; malt extract 20 g/l; temperature 250C; pH 6.5; incubation time 10 days.
The effects of process parameters like pH, temperature, speed and dye wastewater concentration on dye decolorization and degradation were studied for each adsorption process separately.
EFFECT OF TEMPERATURE
Temperature is an important factor that serves as an indicator as to whether the adsorption is an exothermic or endothermic process. If the adsorption is an endothermic process, the adsorption capacity will increase with increasing temperature.
This may possibly due to the increase in the number of active sites and the mobility of the dye molecules at the higher temperature. In contrast, if the adsorption is an exothermic process, the adsorption capacity will decrease with increasing temperature. In this case, a higher temperature may decrease the adsorptive forces between the dye molecules and the active sites on the adsorbent surface.
It is because that dyes molecular diffuse more quickly as the temperature rises, resulting in more opportunity to connect with adsorbents through specific sites.
Maximum adsorption of dye on rice husk fly ash was observed at room temperature. While, there is maximum adsorption of Novacron Brill Red FN 3GL on modified bagasse, modified Hemp and activated carbon at 600C. The optimum condition for adsorption on to coconut shell was found out to be at temp. 600C. Maximum adsorption of dye on lingzhi mushroom was observed at room temperature.
FACTORS AFFECTING ADSORPTION OF DYE
There are many factors which affect the adsorption of dye molecules such as solution pH, initial dye concentration, adsorbent dosage and temperature.
In-depth study and optimization of these parameters will greatly help in the development of industrial-scale treatment process for the dye removal. Thus, these factors will be discussed in the next section.
EFFECT OF SOLUTION pH
The pH of the solution is a very important parameter in the adsorption process, particularly for dye adsorption. The magnitude of electrostatic charges which are imparted by the ionized dye molecules is controlled by the solution pH. As a result, the rate of absorption will vary with the pH of the medium used.
The maximum uptake of methylene blue on activated rice husk was found to be at pH10 . There is no considerable change in adsorption of dye by changing pH, but the maximum dye is adsorbed by bagasse during first 20 min. at alkaline pH.
. The optimum condition for adsorption onto coconut shell was found out to be pH 2, temp. 600C, time 5 hrs.
The effects of process parameters like pH, temperature, speed and dye wastewater concentration on dye decolorization and degradation were studied. The raw material of mushroom collect and it is well preserved in the laboratory. The strain is maintained on solid medium at 40C. the media composition and process conditions were : Agar 20 g/l; malt extract 20 g/l; temperature 250C; pH 6.5; incubation time 10 days.
- Fly ash derived from rice husk is found to be an effective adsorbing material for removal of basic dyes from textile wastewater.
- Tree fern at dry condition adsorbs basic dyes.
- Chemically modified bagasse and hemp stems remove reactive dyes from textile effluent.
- Coconut shells were proved to be an effective adsorbing material for removal of direct dyes from the effluent.
- At the optimized conditions, the maximum coloring material and COD were reduced by lingzhi mushroom.
- Harmful coloring matter can be removed from textile wastewater by using agricultural waste.
- Biodegradable material derived from plant resources could be an effective alternative for activated charcoal for colour removal from textile wastewater.
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