Removal of heavy metals from aqueous media using native cassava starch hydrogel

Graft copolymers of cassava starch and acrylonitrile were synthesized in aqueous solution using ceric ammonium ion as the initiator. Saponification of grafted copolymer was done by reaction with sodium hydroxide and precipitated with methanol. Grafting was confirmed by Fourier transform infrared spectroscopy (FTIR). The grafted copolymer and the hydrolyzed graft copolymer (hydrogel) were used as sorbent for the uptake of heavy metals from the aqueous media. The sorption capacity was evaluated by measuring the extent of sorption of nickel, copper, and leads metals ions, under equilibrium conditions. Using the sorption isotherm models, the Freundlich model was found suitable because of good fitness and equilibrium data yielded the following ultimate capacity values for the sorbent of the grafted copolymer: 54 mgPb/g, 64.5 mgCu/g and 71.1 mgNi/g and for the hydrogel: 72 mgPb/g, 76.6 mgCu/g and 86.5 mgNi/g. Hydrolysis increases the sorption affinity of grafted copolymer toward metal ions. Acid stripping with 2% HCl resulted in 99.6% metal recovery for the hydrogel and 52.2% for the grafted copolymer. This shows the ability of the product to be reused, upon drying between treatments.Key words: Acrylonitrile, cassava starch, grafted copolymer, heavy metals, hydrogel, sorption

Biopolymer-Based hydrogels for agriculture applications: Swelling behavior and slow release of agrochemicals

Hydrogels are cross-linked polymers that can absorb and hold largeamounts of water and aqueous solutions due to the presence of hydrophilic functional groups in their 3D network. These materials also serve as vehicles of different active compounds because they can regulate their release rate. Because of such properties, hydrogels are currently used in many areas including agriculture, mainly as water retention agents for soil conditioning, and as carriers of agrochemicals for their slow or sustained-release. However, most of the hydrogels currently available on the market are based on polyacrylamide and acrylate derivatives, which means that they are not completely biodegradable, i.e. are considered as potential soil contaminants and present certain degree of toxicity. In this context, the development of biodegradable hydrogels for their use in agriculture is gaining interest worldwide. Biopolymers such as chitosan, cellulose, alginate and their derivatives are being explored due to their biocompatibility, biodegradability and low cost. Briefly, in this chapter, recent studies on biopolymer-based hydrogels for their use in agriculture are discussed in terms of their synthesis, swelling behavior, as well as their uses for slow and controlled release of agrochemicals.Fil: Tomadoni, Bárbara María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Casalongue, Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Alvarez, Vera Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; Argentin