Adsorption of paraquat using methacrylic acid-modified rice husk.

This work investigates the adsorption of paraquat from aqueous medium using a methacrylic acid (MAA)-modified rice husk. The carboxyl groups were chemically bound to the surface of the rice husk by graft copolymerization using Fenton's reagent as a redox initiator. The graft copolymerization was examined to determine the H(2)O(2) concentration and the amount of MAA monomer used. FT-IR spectra confirmed the presence of carbonyl groups on the structural units of the rice husk derivative. The MAA-modified rice husks were hydrolyzed to sodium salt and used to adsorb paraquat. The adsorption was rapid in the first few minutes and quickly reached equilibrium. Equilibrium adsorption data are more consistent with the Langmuir isotherm equation than with the Freundlich equation. The maximum adsorption capacity of modified rice husks was 317.7mg/g-adsorbent. This value clearly exceeds the 60mg/g of Fuller's earth and the 90mg/g of activated carbon, which are the most commonly used binding agents for paraquat.

Preparation of acrylic acid-modified chitin improved by an experimental design and its application in absorbing toxic organic compounds.

Chitin grafted poly (acrylic acid) (chi-g-PAA) is synthesized and characterized as an adsorbent of toxic organic compounds. Chi-g-PAA copolymers are prepared using of ammonium cerium (IV) nitrate (Ce(4+)) as the initiator. The highest grafting percentage of AA in chitin obtained using the traditional technique is 163.1%. A maximum grafting percentage of 230.6% is obtained using central composite design (CCD). Experimental results are consistent with theoretical calculations. The grafted copolymer is characterized by Fourier transform Infrared spectroscopy and solid state (13)C NMR. A representative chi-g-AA copolymer is hydrolyzed to a type of sodium salt (chi-g-PANa) and used in the adsorption of malachite green (MG), methyl violet (MV), and paraquat (PQ) in aqueous. The monolayer adsorption capacities of these substances are 285.7, 357.1, and 322.6 mg/g-adsorbent, respectively. Thermodynamic calculations show that the adsorption of MG, MV, and PQ are more favored at diluted solutions. The high adsorption capacity of chi-g-PANa for toxic matter indicates its potential in the treatment of wastewater and emergency treatment of PQ-poisoned patients.

Preparation of methacrylic acid-modified rice husk improved by an experimental design and application for paraquat adsorption.

Methacrylic acid (MAA) grafted rice husk was synthesized using graft copolymerization with Fenton's reagent as the redox initiator and applied to the adsorption of paraquat. The highest grafting percentage of 44.3% was obtained using the traditional kinetic method. However, a maximum grafting percentage of 65.3% was calculated using the central composite design. Experimental results based on the recipes predicted from the statistical analysis are consistent with theoretical calculations. A representative polymethacrylic acid-g-rice husk (PMAA-g-rice husk) copolymer was hydrolyzed to a salt type and applied to the adsorption of paraquat. The adsorption equilibrium data correlate more closely with the Langmuir isotherm than with the Freundlich equation. The maximum adsorption capacity of modified rice husk is 292.5mg/g-adsorbent. This value exceeds those for Fuller's earth and activated carbon, which are the most common binding agents used for paraquat. The samples at various stages were characterized by solid-state (13)C NMR spectroscopy.