Download or read book Removal of Boron from Aqueous Solutions Using Biopolymers and Composites written by Hary Demey Cedeño and published by . This book was released on 2015 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: The growing concern over environmental pollution in recent decades has placed increasing focus on research into the development of sustainable processes associated with the removal of contaminants in waters. Water is scarcer than three decades ago, and there is still no satisfactory solution for the removal of pollutants. One element that has gained worldwide prominence is boron. Although it is a nutrient needed in small amounts for human and plant metabolism, higher levels are toxic to most plants and are associated with reproductive problems in humans. The World Health Organization (WHO) suggests a maximum concentration in drinking water of 2.4 mg/L, but many countries have not yet adopted this recommendation in their water treatment controls. At present, there is no general method for boron removal; several techniques can be used, such as electrodialysis, precipitation, chemical coagulation and electrocoagulation, complexation/nanofiltration, phytoremediation, ion exchange, reverse osmosis and adsorption with different materials. The selection of a particular treatment technology should be made not only on the basis of its efficiency but also with consideration of the associated environmental and financial costs. Biopolymers are a potential solution that has received little attention in the literature. Biopolymers and their derivatives are diverse and abundant in nature; they exhibit fascinating properties and are increasingly important in many applications thanks to their environmentally-friendly characteristics. A small number of publications report the possibility of using tannin gel (Morisada et al., 2011), cellulose cotton (Liu et al., 2007) or chitosan modified with N-methy-D-glucamine (Sabarudin et al., 2005), sugars (Morisada et al., 2011) and diols (Oishi and Maehata, 2013; Fortuny et al., 2014). Biosorption is an effective, simple and cost-beneficial method for the removal of contaminants from waters. This thesis focuses on the development of a sorption-based separation process, using biopolymers and composites for boron removal. The work has been carried out at the Department of Chemical Engineering of the Universitat Politècnica de Catalunya (UPC) in the framework of two research projects (Ref.: CTQ2008PPQ-00417/PPQ and CTQ2011PPQ-22412/PPQ) and the FPI fellowship (BES 2009-026847) financed by the Spanish Ministry of Science and Innovation (MICINN). This work is a continuation of research that has been underway at the Department of Chemical Engineering (UPC) for many years, on the development of advanced separation processes for the removal of valuable compounds or contaminants from aqueous solutions. It contributes to the state of the art on boron separation technologies (examples of which include the development of new composites based on the encapsulation of metal hydroxides in biopolymers). Alginate and chitosan were effectively used as sorbents for boron recovery in the current research. Immobilization techniques were implemented using the technology described by Guibal et al., 2010; active materials are trapped in situ and distributed throughout the polymer support, creating a more stable adsorbent than those obtained by the traditional impregnation method, in which the active material is released partially from the pores of the polymer support while successive adsorption-desorption cycles are performed. Three composite materials have been synthesized in order to improve the sorption capacity, the selectivity towards boron species, and the mechanical properties of the raw sorbents: calcium alginate/alumina (C15l), which improves the sorption capacity of alginate in neutral medium; chitosan/nickel(II) hydroxide [chiNi(III)] and chitosan/Iron(III) hydroxide [chiFer(III)], which increase the sorption uptake of chitosan and improve the handling of hydroxides in the adsorption process, and are stable enough to be used in aggressive environments such as seawater without affecting sorption uptake.