Biodegradable drag reducing agents and flocculants based on polysaccharides: Materials and applications

Abstract

Organic and inorganic flocculants are used in treatment of water and industrial effluents. Polymeric flocculants, synthetic as well as natural, because of their natural inertness to PH changes, low dosage, and easy handling, have become very popular in industrial effluent treatment. It has been established in the authors' laboratory that by grafting polyacrylamide branches on rigid backbone of polysaccharides, the dangling grafted chains have easy approachability to contaminants in effluents. Thus grafted polysaccharides are very efficient, shear stable and biodegradable flocculants. They also exhibit turbulent drag reducing characteristics. Among grafted guar gum, xanthan gum, carboxymethyl cellulose, and starch, grafted starch performs the best. Starch consists of amylose (a low molecular weight linear polymer) and amylopectin (a high molecular weight, branched polymer). The grafted amylopectin is found to be the best flocculant for various kinds of industrial effluents, providing credibility to the above‐cited model. In the present paper, the details about grafted polysaccharides as turbulent drag reducers and flocculants are given, along with their applications.

A Review on Development and Application of Plant-Based Bioflocculants and Grafted Bioflocculants

“…13 Hence, the flocs formed are bigger, stronger and denser with good settling characteristics. 14 In addition, they are easy to handle, immediately soluble in aqueous systems, not sensitive to pH and produce lower sludge volume. 10 However, the potential problems associated with their use are lack of biodegradability and dispersion of monomers or residual polymers in water that may represent a health hazard.…”

“…Biopolymers based flocculants have attracted wide interest from researchers because they have the advantages of biodegradability, non-toxic and easily available from reproducible agricultural resources. 10,14,17 Natural organic flocculants which are based on natural polymers or polysaccharides like starch, cellulose, chitosan, natural gums, mucilage and etc. have been investigated for their flocculating properties in wastewater treatment.…”

Settling rates for flocculation of iron and manganese ore‐containing suspensions by cationic glycogen

“…However, the synthetic polymer flocculants are not shear resistant or biodegradable [1]. By contrast, naturally occurring polysaccharides are shear stable, biodegradable, cheap, and easily available from reproducible farm and forest resources [7,8]; yet they are less efficient flocculants and have a shorter shelf-life due to biodegradability [1].…”

“…Such cationic polymers are being used in waste water carrying high negative charges and are widely used as wet-end additives in paper industry [12][13][14]. One of us previously demonstrated that cationized polysaccharides exhibit higher flocculation than the corresponding unmodified polysaccharides [1,15]. Among various water-soluble polysaccharides, glycogen is most highly branched and has high molecular weight [16,17].…”

“…While water used for direct human consumption and for agriculture cannot be recycled, water used for industrial processes can be reused successfully if purified; and purification is dependent on getting the solid constituents out of suspension without imposing excessive cost. Around the world the application of synthetic flocculants is accepted for solid-liquid separation in the recycling of domestic wastewater and of industrial and mineral processing effluents [1][2][3].…”