Polysaccharides are abundantly available from farm, forest, and microbial resources. They are used in myriad applications. It has been established in the authors' laboratory that their performance is enhanced considerably on purification, grafting by polyacrylamide (PAM), and subsequent hydrolysis as well as cationization. The most significant performance is enhanced in flocculation where it has been found that the modified polysaccharides outperform existing flocculants in national and international markets. Similar effects are observed in their performance in turbulent drag reduction (DR), percolation, and rheology. The present article outlines the details of materials, mechanisms, and practical applications of these novel materials.saccharides may have many low-molecular-weight impurities. The biodegradability of polysaccharides reduces their shelf life and needs to be suitably controlled. In various applications, their required dosages are large and their solutions and flocs lose stability and strength because of biodegradability. However, by purification [5], grafting [5], hydrolysis [6], and cationization [7], useful polymeric materials can be developed for varied applications.Effluent disposal is a major problem nowadays all over the world. Industrial development has created hazards and environmental problems. Hence, environmental concern and depletion of raw material resources have forced scientists and technologists to develop materials from renewable agricultural and plant resources to protect the environment from pollution.Recycling of domestic wastewater, industrial effluents, and mineral-processing effluents has been accepted by the application of synthetic flocculants for solid-liquid separation due to economic and environmental considerations all over the world [8][9][10]. When polymers are involved in a solid-liquid separation by an aggregation process of colloidal particles, the process is termed "flocculation" [10]. In general, flocculation is caused by the addition of a minute quantity of chemicals known as "flocculants". Both inorganic and organic flocculants are used in various kinds of flocculation phenomena [11]. Among the inorganic flocculants, the salts of multivalent metals like aluminum and iron are mostly used. The organic flocculants are essentially polymeric in nature. Both synthetic and natural water-soluble polymers are used as flocculants [8][9][10][11]. Some of the most important types of synthetic polymers are polyacrylamide (PAM), poly(acrylic acid), poly(styrene sulfonic acid), poly(diallyl dimethyl ammonium chloride) (DADMAC), etc., the synthetic effluents are available in all three ionic formscationic, anionic, and nonionic. Among the natural polymers, starch, guar gum, alginates, and products based on chitin, glue, and gelatin are used as flocculants and retention aids. The extensive use of polymers as flocculants is due to their low dosage (1-5 ppm), inertness to pH changes, formation of large cohesive flocs, and versatile tailorability. Large tonnage use of inorganic comp...

The synthesis of glycogen-g-polyacrylamide (Gly-g-PAM) was carried out by a ceric ion-induced solution polymerization technique. Six grades of graft copolymers were synthesized by the variation of catalyst and monomer concentrations. These graft copolymers were characterized by intrinsic viscosity measurements, FTIR spectroscopy, and X-ray diffraction techniques. Flocculation performance of these graft copolymers were done in kaolin suspension. Of the above grades, the graft copolymer Gly-g-PAM 5, which has longer PAM chains, showed best flocculation performance. The flocculation performance of the graft copolymer was compared with commercial flocculants and other PAM-grafted flocculants developed so far in the authors' laboratory. In all the cases, it was found that the graft copolymer performed the best.

A novel biodegradable graft copolymer of dextran (Dx) and 2-acrylamido-2-methyl-1-propane sulphonic acid (AMPS) was synthesized by grafting poly-AMPS chains onto dextran backbone by free radical polymerization using ceric ammonium nitrate (CAN) as an initiator. Different amounts of AMPS were used to synthesize four different grades of graft copolymers with different side chain lengths. These grafted polymers were characterized by elemental analysis, FTIR, 1 HNMR, rheological technique, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and X-ray diffractometry (XRD). They exhibited efficient flocculation performance in kaolin suspension.

ABSTRACT:The partial hydrolysis of xanthan gum-gpolyacrylamide was carried out in alkaline medium. Four grades of partially hydrolyzed products were synthesized by varying the reaction parameters. The neutralization equivalents of these products were determined by titration with standard sodium hydroxide solution. The flocculation characteristics of all the hydrolyzed graft copolymers and the unhydrolyzed xanthan gum-g-polyacrylamide were determined in 5 wt % iron ore and kaolin suspensions. The partially hydrolyzed product with neutralization equivalent of 1000 g showed better performance than that of other partially hydrolyzed products, but all hydrolyzed products exhibited poorer performance than that of the unhydrolyzed product in flocculation.

No abstract