Environmental Science Water Research & Technology PAPER Cite this: Environ. Sci.: Water Res. Technol., 2015, 1, 84 Received 25th July 2014, Accepted 16th October 2014 DOI: 10.1039/c4ew00023d rsc.li/es-water Modified guar gum/SiO 2 : development and application of a novel hybrid nanocomposite as a flocculant for the treatment of wastewater† Sagar Pal, * a Abhay Shankar Patra, ab Soumitra Ghorai, a Amit Kumar Sarkar, a Raghunath Das a and Supriyo Sarkar b Using the sol gel process, a novel hybrid nanocomposite (g-GG/SiO 2 ) has been developed in the authors' laboratory by grafting synthetic polyacrylamide chains on a guar gum backbone (g-GG) in the presence of microwave irradiation followed by in situ nanosilica incorporation on the surface of g-GG. Various characterization methods propose that g-GG promotes silica polymerization and probably acts as a template for nanoscale silica formation. Rheological characteristics indicate the gelling properties of the hybrid material. The application of the composite material in flocculation has been investigated on the laboratory scale as well as on the pilot scale. The flocculation kinetics and mechanism have been explained on the basis of pH of the suspension and flocculant dosage. Because of strong matrix–nanofiller interactions as well as enhanced molecular weight and hydrodynamic radius, the modified biopolymer-based nanocomposite provides excellent potential as a flocculant for the treatment of various synthetic and industrial effluents through a green disposal technique. Introduction Recently, several efforts have been made to synthesize poly- meric nanocomposites for their different applications. 1,2 The sol–gel process is one of the most effective techniques to develop the nanoscale inorganic framework on the surface of natural/modified natural polymers. 3 The strong synergistic effect between inorganic nanofiller and modified poly- saccharide matrix generates hybrid composite materials with remarkable improvement of mechanical, thermal and surface properties compared to the individual components. 4 Because of the interesting properties of hybrid nanocomposite mate- rials, in recent years they have been extensively used for the treatment and remediation of industrial wastewater. 5 The direct disposal of industrial wastewater without appropriate treatment contaminates the water bodies with toxic elements which are extremely harmful towards aquatic species and human health. 6 Therefore, to reduce the toxicity level of wastewater as well as for the possible industrial reuse of treated wastewater, the separation of suspended solids along with other chemical and microbiological contaminants from the aqueous environment is extremely important in the field of wastewater management. 7,8 There are various waste- water treatment methods such as flocculation, precipitation, evaporation, and adsorption. Among these, flocculation is an 84 | Environ. Sci.: Water Res. Technol., 2015, 1, 84–95 This journal is © The Royal Society of Chemistry 2015 a Polymer Chemistry Laboratory, Department of Applied Chemistry, Indian School of Mines, Dhanbad-826004, India. E-mail: sagarpal1@hotmail.com, pal.s.ac@ismdhanbad.ac.in; Fax: +91 326 2296615; Tel: +91 326 2235769 b Tata Steel R&D, Jamshedpur-831 007, India † Electronic supplementary information (ESI) available: Details of settling test/ jar test methods, GPC analysis results (Fig. S1 & S2), table of elemental analysis results (Table S1), HRTEM image of the g-GG/SiO 2 -4 nanocomposite (Fig. S3), rheological characteristics (Fig. S4 & S5), table of settling rate, floc size (Table S2), jar test results (Fig. S6), point of zero charge of the g-GG/SiO 2 -3 nanocomposite (Fig. S7), and parameters of flocculation kinetics (Table S3). See DOI: 10.1039/c4ew00023d Water impact Wastewater generated from various industrial sources exhibits a wide range of toxic suspended particles, coloured wastes and chemical and microbiological contaminants. With the development of a modified biopolymer-based nanocomposite, it is possible to reduce the toxicity level of wastewater. Our work aims at the development and application of a novel modified biopolymer-based nanocomposite, which represents an outstanding contribution for sustainable development in the treatment and recovery of industrial chemical wastes. In comparison to existing systems, the guar gum–silica nanocomposite combines superior flocculation capacity, which improves the performance beyond the state of the art reported in the literature. Here, the synergistic properties between nanosilica filler and modified guar gum matrix contribute a significant technological development for water treatment and sustainability towards the environmental viewpoint. Published on 05 November 2014. Downloaded on 17/03/2015 15:14:06. View Article Online View Journal | View Issue