Nagwa A. Badway

A novel hydrogel based on agricultural waste for removal of hazardous dyes from aqueous solution and reuse process in a secondary adsorption

A novel hydrogel based on the orange peel (OP) and N-vinyl-2-pyrrolidone was prepared by free-radical polymerization using gamma irradiation. The effect of radiation dose and hydrogel composition on gel content was studied. The formed hydrogel was characterized by FT-IR, TGA, and SEM. The swelling behavior was determined as a function of swelling time, pH, and OP content. The hydrogel swelling was found to be pH dependent, and the diffusion mechanism of water into the hydrogel was found Fickian. The developed hydrogel was used for the removal of Congo red (CR) and methyl orange (MO) dyes from wastewater. The effects of various operating parameters, such as initial pH, contact time, initial dye concentration, and temperature on the removal of dyes, have been investigated. The Langmuir and the Freundlich adsorption models were applied to study the adsorption isotherm. The pseudo-first-order model was proved compatible for CR adsorption and the pseudo-second-order model well described the adsorption of MO. The adsorption of dyes increased with increasing temperature indicating that the endothermic nature of the adsorption process and the thermodynamic parameters was evaluated. Second, the adsorption cycle of dyes was also examined and discussed utilizing the loaded hydrogel with the other dye and cobalt metal ions.

Characterisation of alginate-based nanocomposites prepared by radiation for removal of pesticides

Nanocomposites based on sodium alginate (NaAlg) and acrylic acid monomer (AAc) with different concentrations of calcite (C) or xonotlite (X) were prepared using gamma ray radiation. (NaAlg/AAc) hydrogel and its composites were characterised by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The introduction of calcite or xonotlite particles into (NaAlg/AAc) hydrogel increases the swelling capacity. The thermal stability improved by introducing calcite into (NaAlg/AAc) nanocomposite and decreased by introducing xonotlite. The prepared nanocomposites were used for removal of methomyl pesticide. It was found that the removal of methomyl by the nanocomposites is pH-dependent. The adsorption isotherm of various nanocomposites was fitted with Freundlich model. The maximum removal percent of methomyl is sequence in order of (NaAlg/AAc-X) > (NaAlg/AAc-C) > (NaAlg/AAc).

Consecutive Removal of Hazardous Dyes from Aqueous Solutions by Composite hydrogels Based on Rice Straw

The composite hydrogels based on rice straw (RS) and N-vinyl-2-pyrrolidone (NVP) or acrylamide (AAm) were successfully prepared by gamma irradiation. The effect of the radiation dose and the monomer content on the gel percent was studied. The composite hydrogels were confirmed by (FTIR), (TGA) and (SEM). It was found that the diffusion of water into the prepared composites was Fickian character. The removal of congo red (CR) and methyl orange (MO) dyes by (NVP/RS) and (AAm/RS) composite hydrogels were investigated as a function of the pH, contact time, initial dye concentration solution and temperature. It was achieved that the adsorption capacity of (NVP/RS) composite hydrogel towards (CR) and (MO) was higher than (AAm/RS) one. The kinetic data was tested by the pseudo-first-order and the pseudo-second-order kinetic models. The adsorption isotherm was closely fitted with the Freundlich model for adsorption of CR and MO onto (NVP/RS) and the Langmuir model for adsorption of the dyes onto (AAm/RS). A high adsorption capacity was obtained in the second adsorption cycle of MO onto the composite hydrogels loaded with CR. Improvement in the adsorption of MO onto (NVP/RS) and (AAm/ RS) composite hydrogels loaded with Co(II).