**Abstract**

Water represents one of the essential resources on earth, and all living organisms rely on it for survival. However, freshwater systems are directly under serious threat by human activities. A recent World Health Organization report has estimated that 2 billion people use contaminated water sources. The major organic contaminants in water bodies include organic dyes. These are directly related to the spread of diseases owing to their allergenic, mutagenic, and carcinogenic characteristics. Dyes occur in the environment through untreated industrial effluents. Also, the advancement in human civilisation cannot be considered without the development of modern industries. However, an attempt to limit the resulting impacts of coloured effluents on global freshwater quality has become the focus of recent research. For this reason, the use of efficient, simple, and low-cost methods for the treatment of dyes-containing industrial wastewater could serve as a useful tool. An effort to meet the demand for "green chemistry" and sustainable development has led to several investigations on polysaccharide-based adsorbents. This chapter exposes a critical discussion on the literature concerning the biopolymeric xanthan gum and *kappa*-carrageenan polysaccharides as adsorbents for dye removal in an aqueous medium. Functionalisation of these biopolymers through graft copolymerisation and inclusion of inorganic nanoparticles for improved adsorption performance is systematically elaborated.

**Keywords:** xanthan gum, *kappa*-carrageenan, grafted polysaccharides, nanocomposite, dyes, adsorption

### **1. Introduction**

Water is a precious resource indispensable for the sustainability of life on earth. It is vital to human well-being and economic development. However, safe water remains a significant issue around the world [1]. According to a recent report by the World Health Organization (WHO 2019), approximately 785 million people lack clean water for their basic needs. Supplying water to an increasing global population necessitates concurrent consideration of several societal sectors that compete for limited resources [2]. For that reason, a vast majority are dependent on surface water and groundwater for drinking purpose. The WHO report also highlights the fact that more than two million people die every year from the use of unsafe drinking water. This is well-reported to spread sickness and waterborne diseases such as typhoid and cholera. This situation emerges from the occurrence of pollutants as a result of the environmental disposal of untreated effluent released by human activities [3]. Indeed, it is inconceivable to achieve progress in human civilisation without industrialisation. However, its exponential development in a competitive era and an increasing global population has seriously impaired the quality of freshwater systems.

Among an assortment of environmental pollution, waterbody contamination owing to the discharge of untreated water-containing organic species has attracted significant consideration in recent years [4, 5]. Organic dye-containing wastewater from industries such as textiles, petrochemical, cosmetics, papers and plastics, for example, has been described for their carcinogenic and mutagenic nature [6]. Also, the organic dyes are oxygen-sequestering agents capable of reducing light penetration in the water systems and thereby restraining the photosynthesis of aquatic vegetation [7, 8]. **Figure 1** illustrates the fate of organic dyes in the natural environment. Thought the textile industry had played an enormous role in the development of the South African economy [9], this has also significantly impacted the water resources. The dye-containing effluents disposed to the environment without proper treatment can be highly toxic even at a concentration lower than one ppm [10]. Therefore, the removal of toxic organic dyes from contaminated effluents before being discharged into the environment has evoked considerable attention.

From the commercial and environmental viewpoint, the focus of this chapter is to provide a comprehensive discussion on the ability of natural polymers to perform as adsorbents for industrial wastewater remediation. The hybridisation of these

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feasible regeneration [29, 30].

*Nanoengineered Polysaccharide-Based Adsorbents as Green Alternatives for Dye Removal…*

**2. Treatment of dye-contaminated water in adsorption procedure**

biomaterials by grafting of segments and combination with inorganic nanoparticles is presented as an ideal strategy to improve their inherent characteristics and sorp-

Several techniques have been reported to be able of alleviating the occurrence of organic dye in contaminated industrial effluents, and these include flocculation, membrane filtration, biodegradation, chemical degradation, and photochemical treatment [11]. Although these treatment procedures have been applied successfully, they have also displayed shortcomings like high operational costs, low selectivity and toxic sludge production. Adsorption procedure, on the other hand, has frequently been described as a promising approach for wastewater treatment because of the reasons like simplicity in design, low operational cost and comparatively high efficiency [12, 13]. Furthermore, this treatment procedure can be applied on a large scale, as it can handle large flow rates and yields a high quality of

Numerous adsorbents are reported in the literature for the removal of contaminants in wastewater, and these include activated carbon, clay minerals, zeolites, industrial wastes, metal oxides, and polymeric materials [15–20]. Among these adsorbents activated carbon is the most widely employed material for the removal of dye in aqueous solution due to its high surface area [21]. However, activation of carbon sources is energy-intensive and requires the use of expensive chemicals and equipments. The low regeneration of spent activated carbon also restricts its practical application. A large majority of the reported adsorbents are also associated with drawbacks like non-biodegradability and low efficiency. These limitations can be overcome using naturally occurring "green" polysaccharide adsorbents owing to

**3. Polysaccharide adsorbents for the removal of organic dye in aqueous** 

Polysaccharides are hydrophilic, non-toxic, and relatively cheap polymers consisting of repeating subunits of sugar linked with glycosidic bonds. The composition and sources of polysaccharides that are generally investigated for their potential to act as adsorbents in aqueous media are presented in **Table 1** [22–25]. The adsorption ability of these biomaterials is due to the occurrence of functionalities such as hydroxyl (-OH), sulphonic acid (-SO3H), the carboxylic acid (-COOH), amino (-NH2) and amide (-CONH2) groups which can serve as binding sites [26]. This feature, complemented with the porous nature, make polysaccharides good candidates for water treatment applications. Some of the commercially available polysaccharides include cellulose, starch, guar gum, chitosan, xanthan gum and carrageenan. Among these, eco-friendly xanthan gum and carrageenan (**Figure 2**) with the ability to form gel have been gaining considerable attractions recently [27, 28]. So far, these have been described to be among the most effective adsorbents for the removal of toxic dyes in aqueous solution due to

Among these, eco-friendly xanthan gum and carrageenan (**Figure 2**) with the ability to form gel have been gaining considerable attractions recently [27, 28]. So far, these have been described to be among the most effective adsorbents for the removal of toxic dyes in aqueous solution due to their tunable surface chemistry and

*DOI: http://dx.doi.org/10.5772/intechopen.94883*

water without producing sludge and residuals [14].

their cost-effectiveness, ease availability, and biodegradability.

their tunable surface chemistry and feasible regeneration [29, 30].

tion capacity.

**solution**

**Figure 1.** *The fate of the dye-contaminated effluent in the aquatic environment.*

biomaterials by grafting of segments and combination with inorganic nanoparticles is presented as an ideal strategy to improve their inherent characteristics and sorption capacity.
