Dye high demand for textile products and

Dye is asubstance that is used forimparting colour to alter the existing colour shade to a substrate. Dye becomesan incredible material as it has an ionising yet an aromatic organic compound that possesses an affinity towards the materialbeing applied (Zhong et al., 2010). Unlike paint, they do not build on uponthe material surface but being absorbed into the pores of the material because dye molecule has a smaller size than the pores of the material.

It is chemically bonded to thesurface and become a part of the material. However, the extensive usage of dyes inindustries produced a large amount ofwastewater with intense colour and the colour is highly visible even in a smallquantity. The growth of industries also increasesthe discharge of residual colour metal in water as they need a substantialamount of water in their manufacturing process. Besides, the high demand fortextile products and also increased the usage of synthetic dyes both havecontributed to the severe water pollution. There is also no official documentthat states the limiting amount of colour that can be discharged in theeffluents (Zhong et al., 2010). This is why the unlimited amount of dyesare released into the water are stillcontinuing until today.              Cationic dyes, also known asbasic dyes are a class of synthetic dyes.

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This coloured compound is called basic dyes because it contains a positive electrical charge which is attracted to thenegative charge on fibre molecule to form a salt. Basic dyes are effectivecolouring agent and it can be applied to many textiles including wool, silk andcotton. Methylene blue (MB) is one type of cationic dyes which is blue incolour. It is popularly used as a colourantin food, paper and also dying cotton and wools. Unfortunately, when MB is disposed in water without treatment, it couldcontribute to major water pollution and aquatic organisms will die. MB dyes areconsidered toxic and have carcinogenic properties. Therefore, the removal ofthis dyes from wastewater is vital to protect the environment as well as thewell-being (Gottipati& Mishra, 2010). Recently, manyconventional methods that have been used to remove dyes from the water involveshigh cost, difficult to apply, and produce chemical sludge (Bhatnagar& Minocha, 2006).

These physical, biological and chemicalmethods were investigated to clear up the colour of wastewater but have been relatively ineffective.  Biological methodstake a long time to degrade the dyes while chemical method can causepollution to the water being treated (Shendkar et al., 2013). A more effective and cheaper ways are strictly needed to treat wastewater thatused only small amounts of chemical and energy. Adsorption is a well-known technique thathas been observed to be a better technique because of the simplicity andflexibility, easy to operate and most importantly does not form dangerous substances (Khan et al., 2005).

The most popular adsorbent used isadsorbent but it is an expensive process. Thiscause number of research work have been studied to find efficient andlow-cost adsorbent to remove Methylene blue dyes from wastewater (Ehrampoosh,2011). Biomass refers to none – fossilised and biodegradable organic materials originatesfrom a plant, animal and microorganisms.The use of biomass as an adsorbent can reduce the emission of carbon dioxide aswell as the greenhouse effect (Umoren et al.

, 2013). In this study, the fruit shell of Cassia fistula is studied as anadsorbent to evaluate the efficiency of this plant for the removal of Methyleneblue dyes in aqueous solution. In the previousstudy, the ash of Cassia fistula seedhas been used to adsorb Congo red dye from aqueous solution (Amuda et al.

, 2014). The results concluded that it has aconsiderable potential as an adsorbent in the future.Dyes are basically an organic compoundthat can bind themselves to surface in order to provide a bright and long-lasting colour. The discharge of dyes intothe water streams causes many diseases to human and an environment where the growth of bacteria is blocked and can causeharm to aquatic life (Rahman et al., 2012). Most of them are complex molecules andresistance to many things such as the action of detergent (Amrhar et al.

, 2015).       Several conventional methods that are already existed for the treatmentof coloured wastewater including chemical, biological and physical method hasbeen proved to be limited in small and medium scaled industries. Dyes aredifficult to biodegrade even after extensive treatment, so the colour mightstill present in the water. They were less efficient, difficult to apply,expensive process, produce sludge and also use electricity. Thus, adsorptionprocess is done to remove Methylene blue dyes by using adsorbent obtained from the fruit shell of Cassia Fistula.       The aim of this research is to investigate thepotentiality of Cassia fistula’sfruit shell as an adsorbent for removing Methylene blue dyes from aqueoussolution. Specific objectives include:a)     Toproduce adsorbent from Cassia fistula’s fruitshell.b)     Tostudy the effect of different parameters including adsorbent dosage, pH, MBconcentration, temperature and contact time.

c)     Tocharacterise the adsorption of dyes usingmoisture content, ash content, bulk density, SEM, FTIR, and pHpzc studies. d)    Todetermine the adsorption isotherm of MB over the adsorbent produced. This study can contributeto a clean environment as it helps toreduce water pollution. The degradation of the environment has become a seriousproblem for the existence and survival of human beings as well all life onEarth. Water pollution due to dyeing industry is one of the heavily pollutingindustries because a large quantity ofeffluent is being discharged into thewater. This research can contribute to the alternatives of treating thewastewater. The adsorbent used in this study is a low-cost adsorbent and this natural adsorbent will not cause anyharm to our Earth.

The widespread of uses of adsorbent as a method for watertreatment is strongly recommended due to the higher efficiency, low cost and flexible technique. This research alsocan be used in the present industry toadsorb dye released by the factory beforefurther treatment.This study focus on the use of biomassfrom the fruit shell of Cassia fistula. Theadsorbent produced were then tested on the adsorptionof Methylene blue dye. The colour reduction of the dye at different initialconcentration of MB, adsorbent dosage, temperature, initial pH and contact timeis observed in this study.Dyesare a coloured compound and are beingapplied to numerous substrates for example to textiles, paper and also foods (Dash, 2010).

Dyes contain chromophores to give rise to colour and the other group, auxochromes such as carboxylic acid to enablethe bonding to fibre and modify the colour. Dyes can be produced from bothnatural and synthetic sources. Natural dyes are organic compounds mainlyderived from natural sources without any chemical process. A great source ofthis dyes is from plants, animals,insects, and minerals. Due to increase in population and industrial activities,natural dyes do not meet the global demands and their application has been limited mainly in the food industry (Dawood & Sen, 2014).Table 2.

1 above shows the most commonnatural dyes used in textile industries. Syntheticdyes have become popular due to its long-lasting colour, variety choices of colourand would not lose their pigmentation as easily as natural dyes. These are thereasons why synthetic dyes have evolvedinto a multi-billion dollar industry. Synthetic dyes made up from chemicalcompounds that may contain elements such as mercury, chromium, lead, benzeneand toluene.

(Maria et al., 2013).Being exposed to these elements can be very dangerous to human body andenvironment because it has high toxicity.Mainly,dyes are classified based on the usage in textile industry such as anionic,cationic and non-ionic dyes (Pathania et al.,2017).Cationic dyes are also called as basic dyes because it has positive ions in themolecular structure of chromophores. This class of synthetic dyes are watersoluble and form a colouredcationic salt which then reacts with theanionic structure on the substrate surface (Filipi & Milichovský, 2014).

There are applied to substrate with anionic character to produce bright shades with high tinctorial values. MethyleneBlue (MB) also known as methylthioninium chloride is heterocyclic aromaticcompounds with a molecular formula of (C16H18N3CSI.H2O).It appeared as a solid, dark green powder at room temperature and produces ablue solution when dissolved in water.

The chemical structure of MB is shown in Figure 2.1.Methylene blue is one of the cationic dyes which is used in textile industryfor example dyeing of cotton and wools. MB is widely used in humanand medicine for therapeutic and diagnostic procedures including as a stain inbacteriology and also antiseptic and disinfectant (Prasad & Santhi, 2012).

In medicine, Methylene blue was the first synthetic drug to be createdoriginally used as a malaria treatment (Koch, 2013).MBalso commonly used by a biologist as adye to assist in the identification of bacteriaand widely used as a bacterialinfection preventive. Although MB is not strongly hazardous, it can causeharmful side effects to human and aquatic animals (Umoren et al., 2013).Thecommon side effects include vomiting, high blood pressure and also allergicreactions (Pathania et al.

, 2017).Waterpollution is a worldwide problemparticularly in a textile industry where large quantities of dyes are discharged to thewastewater from dyeing process. As textile industries have been the largest consumer of dyes, the demand fordye in the world will continue to rise in the incoming years because ofincrease in human population. Theeffluent of dyestuff from textile industry was declared as one of the majorsource of water pollution within the global when considering of both volume andcomposition of dyes (Dasuqkhi et al.

,2013).The stability and fastness of dyes attractthe producers of dyes and they are consequently producing dyestuff which is more difficult to degrade after being used.  Thereleased of dyes into the wastewater causesevere detrimental effects on a humanbeing and aquatic life.

For a human being,these intermediates can damage the vital organs such as heart, brain, kidneyand central nervous system. They also can interferethe transmission of sunlight for the photosynthetic activity of aquaticorganisms (Maryam, 2013).Most of the dyes areconsidered toxic and have carcinogen properties which make the water inhibitor to aquatic life. As dyes are designedto resist breakdown with time, it cannot be easily removed by conventionaltreatment due to their complex structure and synthetic origins (Ehrampoosh, 2011).Therefore, it is urged for the researcherto find out the way to removes such toxic dyes from the wastewater.Theoretically,there is a great number of separation processes tailored to remove dyes such asa conventional method. Conventionalmethod consists of a combination of the physical, chemical and biological process. Someof the disadvantages of this treatment are the constant high electrical energyrequirement, high cost for supervision, maintain and also construction.

Thereis also some issues of ecological disposal of the sludge waste (De Filippis etal., 2013).Table 2.2 shows some advantages and disadvantages of conventional treatment forwastewater. Biological methods are applied in industrial effluents so that microorganisms such asbacteria, yeast, algae and fungi able to build up and degrade differentpollution. However, their application is restricted because of technicalconstraint. It also requires a large area and hasless flexibility in operation (Sharma, 2014).

Despite many organic molecules are degraded, other molecules are recalcitrant due to their complicated chemicalstructureCoagulationis one example of a chemical method whichis an expensivemethod and creates a disposal problem although the dyes are removed.There is also the possibility that a secondary pollution problem will arise because of excessive chemical used (Tripathi & Ranjan, 2015).Recently, other techniques known asadvanced oxidation technique has beenapplied successfully to degrade pollution but they are very costly and consumehigh chemical reagents (Lopez-Nuñez etal., 2014).

Physicalmethods such as membrane-filtration arethe prime method used in drinking water and wastewater treatment (Kharub, 2012).Generally, the dye molecule will clog the membrane and limits the separationprocess afterwards. It also has a limitedlifetime before membrane fouling happened. Adsorption by adsorbent has been apopular method to treat wastewater but its widespread use is restricted due tohigh cost. Therefore, adsorption by using low-costadsorbent become great alternatives tothe adsorbent.

It is a popular separationprocess and an effective approach for water treatment due to its low initialcost, flexible, simple design, ease of operation and does not result in theformation of harmful substances (De Filippis etal., 2013). The adsorbent is the material uponwhose surface the adsorption takes place. Adsorption is the accumulation ofparticles (adsorbate) at the surface of a solid or liquid (adsorbent). Thebasic principle for adsorption is the mass transfer of a molecule from a liquidinto the solid surface. The adsorbent ismanufactured in such a way as to produce porous particles to attract and holdsorganic molecules.

This process occurs because:                               i.           The contaminant has lowsolubility in the liquid or gas                             ii.           The contaminant hasgreater affinity for the adsorbent than for the liquid                           iii.           The combination of two Major types of adsorbents used are activatedalumina, silica gel, activated carbon,molecular sieved and organic polymers (Christmann, 2011).Most adsorbents such as adsorbent aremanufactured but a few such as zeolites occurnaturally. Each adsorbent has its owncharacteristics such as porosity, pore structure and the nature of itsadsorbing surfaces (Bash, 2015).

Adsorbent isamazingly useful in many applications and industries including drying, humiditycontrol and remediation task. They are applied in industry for semiconductors,pharmaceuticals, food processing, packaging, energy production, pollutioncontrol and waste management. In food processing, for example, the adsorbent isused to make food and other product last longer in a damp environment. Inrecent times, several approaches for the growth of economic and potent adsorbent have been studied including low-cost adsorbent obtained from biomass forremoval of dyes. Some of the adsorbents have been efficiently used  (Radenovi et al,2011). The bonds that form between solute molecules and specificsurface chemical groups have all the properties of true chemical bonds and arecharacterized by relatively large heats of adsorption Theeffects of four adsorption variables which are initial concentration of MB,adsorbent dosage, temperature, initial pH, and contact time are investigated inthis study. Thedistribution of dye molecule between the liquid phase and the adsorbent is ameasure of the position of equilibrium in the adsorption process and can beexpressed by one series of isotherm models.

The adsorption isotherm models are utilised to describe the interaction behaviouramong adsorbate and adsorbent (García et al.,2014). In this study,Langmuir and Freundlich isotherm models were used to describe the adsorptionequilibrium data from the adsorption of methylene blue.

TheLangmuir isotherm describes that the adsorption of MB onto the surface ofadsorbent requires three assumptions (Pathania et al., 2017):·        The surface of theadsorbent is in contact with a solution containing an adsorbate which isstrongly attracted to the surface.·        The surface has aspecific number of sites where the solute molecules can be adsorbed ·        The adsorption involvesthe attachment of only one layer of molecule to the surfaceTheLangmuir adsorption isotherm has been successfully applied to many pollutantadsorption processes (Chairgulprasert etal.

, 2013)Langmuir model is described by the following Equation (3):  =  + . Ce                              (Equation 1)whereKL (L/mg) is Langmuir constantand qmax (mg/g) is the maximum adsorption capacity.TheFreundlich isotherm model describes that the adsorption of solutes from aliquid to a solid surface (Hashem & El-Khiraigy, 2013).The Freundlich model can be represented by Equation (4):Inqe = In KF +  InCe                                              (Equation 2)whereCe (mg/L) is the equilibrium concentration of dye in solution, qe (mg/g) is the amount of dyes adsorbed at equilibrium.

KF and 1/nare Freundlich constant where n indicates the degree of to which an adsorptionprocess is favourable and KF (mg/g)(L/mg)1/n is theadsorption capacity of the adsorbent.  

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