A high-capacity cationic hydrogel adsorbent (CHA) was prepared by polycondensation using triethylenetetramine, acetone and formaldehyde as raw materials. Batch and fixed-bed column experiments were conducted to investigate the adsorption of Acid Black 1 from aqueous solution by CHA. The adsorption mechanism was discussed with respect to its characteristics. Experimental results showed that the adsorption was attributed to a combination of electrostatic attraction and intermolecular interactions between the functional groups of the hydrogel and the dye. The high adsorption capacity of CHA was due to its high cationic charge density and abundant functional groups. Langmuir isotherm fitted well to the equilibrium data and the adsorption process followed pseudo-second-order and intraparticle diffusion kinetic models . The diffusion of dye molecules inside the hydrogel was found to govern the mass transfer process. Good adsorption performance was also observed in the continuous column experiments. The adsorption capacity increased with increasing bed height and decreased with increasing feed flow rate . Overall, the results reported here indicated that CHA could be used as a promising adsorbent for the removal of anionic dyes from wastewater.
Wenxia Wang,Guohe Huang,Chunjiang An,Xiaying Xin,Yan Zhang,Xia Liu
From the viewpoint of sustainability, biomass adsorbent has a high potential in pollution control and there is an emerging interest to investigate the behaviors of pollutants at the interface between biomass adsorbent and solution. This study investigated the performance of cetyltrimethylammonium bromide surfactant-modified flax shives (MFS) for removal of anionic azo dyes from aqueous solution. The equilibrium and kinetic analysis for the adsorption of Acid Orange 7 (AO-7), Acid Red 18 (AR-18) and Acid Black 1 (AB-1) on MFS were conducted. The surface of MFS was characterized by synchrotron infrared and SEM analysis. The absorbed amount of three anionic azo dyes varied with the change of adsorbent dosage, pH and ionic strength. The adsorption isotherm data well fit to the Langmuir model. The adsorption process followed the pseudo-second-order kinetics and the liquid film diffusion models. Thermodynamic studies indicated that the adsorption of three anionic azo dyes was spontaneous. The adsorption of AR-18 and AB-1 onto MFS was endothermic while the adsorption of AO-7 was exothermic. The results can help better understand the behaviors of organic pollutants at biomass adsorbent-water interface. They also present the potential of using MFS as a suitable adsorbent for the removal of anionic azo dyes from wastewater.
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