Itaconic Acid Grafted Starch Hydrogels as Metal Remover: Capacity,Selectivity and Adsorption Kinetics

Hydrogels were synthesized by free radical graft copolymerization of itaconic acid (IA) onto corn starch (S-g-IA). For this purpose, potassium permanganate (KMnO₄)-sodium bisulfite (NaHSO₃) was used as redox initiation system. The formation of grafted starches was confirmed by Fourier transform infrared spectroscopy, wide angle X-ray scattering, thermogravimetric analysis and scanning electron microscopy. The effect of monomer concentration, neutralization, addition of crosslinking agent, N,N-bismetilenacrilamide (MBAm), and initiator concentration on grafting efficiency and adsorption capacity of the starch hydrogels was investigated. It was demonstrated that the introduction of carboxyl and carbonyl groups promoted starch hydration and swelling. Grafting degree increased with the decrease of monomer concentration, increase of initiator concentration, grade of neutralization and the addition of MBAm without neutralization. Remarkably the resulting materials exhibited water absorption capacities between 258 and 1878% and the ability to adsorb metal ions. It was experimentally confirmed the metal uptake, obtaining the higher adsorption capacity (q _e  = 35 mg/g) for the product prepared with the pre-oxidation and lower initiator concentration. The removal capacity order was Pb²⁺>Ni²⁺>Zn²⁺>Cd²⁺. Moreover, the experimental kinetic and the equilibrium adsorption data for Ni²⁺ and Pb²⁺ were best fitted to the pseudo-second order and Freundlich isotherm models, respectively. This work describes for the first time the preparation of metal removal hydrogels based on starch and itaconic acid using the pair redox system KMnO₄/NaHSO₃, which avoids the starch hydrolysis and allows itaconic acid grafting incorporation without the requirement of more reactive comonomers.     

Spanish agriculture from 1900 to 2008: a long-term perspective on agroecosystem energy from an agroecological approach

Regional Environmental Change - According to the agroecological approach, energy analyses applied to agriculture should provide information about the structure and functions of the agroecosystem;...     

Radon progeny activity on skin and hair after speleotherapeutic radon exposure

The objective of present investigation was to measure radon progeny activity on hair and skin (forehead, paraumbilical, paravertebral) and its decrease after speleotherapeutic radon exposure in the gallery of the Gasteiner Heilstollen. Radon progeny activity was measured by means of a halogen-quenched Geiger-Mueller tube with a mica window (density 1.5-2.0 mg/cm2) and an effective diameter of 45 mm; beta efficiency 32% (210Bi), alpha efficiency 18% (241Am). Results are in counts per minute (cpm). All 17 patients were being treated for rheumatic disease in the galleries of the Gasteiner Heilstollen Hospital. The following activity (mean +/- standard error of the mean) was measured 25 (+/- 5) min after leaving the treatment area: on hair of the head, 1235+/-141 cpm; forehead, 503+/-78 cpm; paraumbilical 460+/-85 cpm; paravertebral, 270+/-39 cpm. Taking a shower did not significantly reduce radon progeny activity. Speleotherapeutic radon exposure causes a considerable increase in radon progeny activity on skin. The large surface of hair causes much greater activity on hair than on skin. Owing to their high adhesive properties, radon progenies are not reduced by taking a shower.