Dye removal of AR27 with enhanced degradation and power generation in a microbial fuel cell using bioanode of treated clinoptilolite-modified graphite felt.

This work studied the performance of a laboratory-scale microbial fuel cell (MFC) using a bioanode that consisted of treated clinoptilolite fine powder coated onto graphite felt (TC-MGF). The results were compared with another similar MFC that used a bare graphite felt (BGF) bioanode. The anode surfaces provided active sites for the adhesion of the bacterial consortium (NAR-2) and the biodegradation of mono azo dye C.I. Acid Red 27. As a result, bioelectricity was generated in both MFCs. A 98% decolourisation rate was achieved using the TC-MGF bioanode under a fed-batch operation mode. Maximum power densities for BGF and TC-MGF bioanodes were 458.8 ± 5.0 and 940.3 ± 4.2 mW m-2, respectively. GC-MS analyses showed that the dye was readily degraded in the presence of the TC-MGF bioanode. The MFC using the TC-MGF bioanode showed a stable biofilm with no biomass leached out for more than 300 h operation. In general, MFC performance was substantially improved by the fabricated TC-MGF bioanode. It was also found that the TC-MGF bioanode with the stable biofilm presented the nature of exopolysaccharide (EPS) structure, which is suitable for the biodegradation of the azo dye. In fact, the EPS facilitated the shuttling of electrons to the bioanode for the generation of bioelectricity.

Removal of hazardous pharmaceutical dyes by adsorption onto papaya seeds.

Papaya (Carica papaya L.) seeds were used as adsorbent to remove toxic pharmaceutical dyes (tartrazine and amaranth) from aqueous solutions, in order to extend application range. The effects of pH, initial dye concentration, contact time and temperature were investigated. The kinetic data were evaluated by the pseudo first-order, pseudo second-order and Elovich models. The equilibrium was evaluated by the Langmuir, Freundlich and Temkin isotherm models. It was found that adsorption favored a pH of 2.5, temperature of 298 K and equilibrium was attained at 180-200 min. The adsorption kinetics followed the pseudo second-order model, and the equilibrium was well represented by the Langmuir model. The maximum adsorption capacities were 51.0 and 37.4 mg g(-1) for tartrazine and amaranth, respectively. These results revealed that papaya seeds can be used as an alternative adsorbent to remove pharmaceutical dyes from aqueous solutions.

Development of a membrane-less dynamic field gradient focusing device for the separation of low-molecular-weight molecules.

Dynamic field gradient focusing uses an electric field gradient generated by controlling the voltage profile of an electrode array to separate and concentrate charged analytes according to their individual electrophoretic mobilities. This study describes a new instrument in which the electrodes have been placed within the separation channel. The major challenge faced with this device is that when applied voltages to the electrodes are larger than the redox potential of water, electrolysis will occur, producing hydrogen ions (H+) plus oxygen gas on the anodes and hydroxide (OH(-)) plus hydrogen gas on the cathodes. The resulting gas bubbles and pH excursions can cause problems with system performance and reproducibility. An on-column, degassing system that can remove gas bubbles "on-the-fly" is described. In addition, the use of a high capacity, low-conductivity buffer to address the problem of the pH shift that occurs due to the production of H+ on the anodes is illustrated. Finally, the successful separation of three, low-molecular-weight dyes (amaranth, bromophenol blue and methyl red) is described.

Fast removal and recovery of amaranth by modified iron oxide magnetic nanoparticles.

The adsorption and removal of amaranth (AM) from an aqueous solution by iron oxide nanoparticles (IONPs) coated with cetyltrimethylammonium bromide (CTAB) as adsorbent was reported. The novel magnetic separation was quite efficient for the adsorption and desorption of AM. In an aqueous solution of AM at 25 degrees C, the adsorption data could be fitted by the Langmuir equation with a maximum adsorption amount of 1.05 mg mg(-1) and a Langmuir adsorption equilibrium constant of 0.90 Lmg(-1). The effect of temperature, pH of aqueous medium, electrolyte concentration, composition of desorbent solvent and interfering ions on the recovery process were also investigated. Methanol was used for desorption of adsorbed AM. Due to the absence of internal diffusion resistance both adsorption and desorption of AM were fast and could be completed within 5 min. The results indicated that the CTAB-coated IONPs could be employed in the removal of the anionic dye from wastewater. The AM was removed successfully in spiked samples of Karoon River water.

Use of waste materials--Bottom Ash and De-Oiled Soya, as potential adsorbents for the removal of Amaranth from aqueous solutions.

Bottom Ash, a power plan t waste material and De-Oiled Soya, an agriculture waste product were successfully utilized in removing trisodium 2-hydroxy-1-(4-sulphonato-1-naphthylazo)naphthalene-3,6-disulphonate--a water-soluble hazardous azo dye (Amaranth). The paper incorporates thermodynamic and kinetic studies for the adsorption of the dye on these two waste materials as adsorbents. Characterization of each adsorbent was carried out by I.R. and D.T.A. curves. Batch adsorption studies were made by measuring effects of pH, adsorbate concentration, sieve size, adsorbent dosage, contact time, temperature etc. Specific rate constants for the processes were calculated by kinetic measurements and a first order adsorption kinetics was observed in each case. Langmuir and Freundlich adsorption isotherms were applied to calculate thermodynamic parameters. The adsorption on Bottom Ash takes place via film diffusion process at lower concentrations and via particle diffusion process at higher concentrations, while in the case of De-Oiled Soya process only particle diffusion takes place in the entire concentration range.