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Adsorptive studies were carried out on four synthetic vinyl polymer tanning agents removal from aqueous phase onto wastewater activated sludge (AS). Batch experiments investigated the effects of contact time, dosage of adsorbate, extracellular polymeric substances (EPS), coexisted cations, and physical property of sludge flocs on the four vinyl polymers removal by AS to evaluate the kinetics, isotherms, and mechanisms. Almost 96% of polydiallyldimethylammonium chloride-acrylic-acrylamide (PDM-AA-AM), 90% of polydiallyldimethylammonium chloride-acrylic (PDM-AA), 82% of polydiallyldimethylammonium chloride-acrylic-acrylamide-hydroxyethyl acrylate (PDM-AA-AM-HEA), and 56% of polydiallyldimethylammonium chloride (PDM) were removed from aqueous solutions. The kinetics process of adsorption can be described by the pseudo-second-order kinetic equation and the adsorption isotherms fitted to the Langmuir model very well. The adsorption capacity increases with the increase in initial vinyl polymers concentration. Coexisted cations (Ca2+, Na+) in aqueous solution restrained vinyl polymers adsorption on AS. The presence of Cr3+ions slightly improved the PDM-AA, PDM-AA-AM, and PDM-AA-AM-HEA removal, whereas retarded the PDM removal in some extent. AS are more effective than inactivated sludge in the removal of vinyl polymers. All the four vinyl polymers showed a decrease in the degree of removal when EPS was partial extracted from the biomass. The adsorption mechanisms of AS for vinyl polymers included hydrophobic interaction, surface binding, and electrostatic force. Surface binding may play a major role in PDM-AA, PDM-AA-AM, and PDM-AA-AM-HEA adsorption, while electrostatic interaction may play a major role in PDM removal. This study provided strong evidence that AS can be employed for an effective solution for vinyl polymers syntans removal. [ABSTRACT FROM PUBLISHER]

Hexavalent chromium in aqueous environment may result in severe environmental and public health problems. In this study, short-chain polyaniline/palygorskite composites (PANI/PA) were prepared and developed to remove aqueous Cr(VI). Characterized results showed that short-chain polyaniline was successfully incorporated on the surface of PA. The maximum Cr(VI) adsorption amount was found to be 11.54, 14.34, and 16.22 mg/g at 15, 25, and 35°C, respectively, and polyaniline on the adsorbent surface may account for the enhanced Cr(VI) adsorption. Cr(VI) adsorption was highly dependent on both solution pH and ionic strength, which indicates that electrostatic force and anion exchange may account for the increased Cr(VI) adsorption onto PANI/PA. Cr(VI) saturated PANI/PA can be easily desorbed in alkaline solution and regenerated adsorbents still possess high adsorption amount for aqueous Cr(VI). The current study shows that PANI/PA can be used as an effective and recyclable adsorbent for the removal of Cr(VI) in water and wastewater treatment. [ABSTRACT FROM PUBLISHER]

In this study, the removal potential of vinyl polymer/ZnO nanocomposite (PDM/ZnO) by activated sludge (AS) biomass was investigated. PDM/ZnO was effectively removed by AS adsorption (90.3% of total PDM/ZnO removed). The effects of contact time, temperature, pH of the solution, PDM/ZnO production method, initial adsorbate concentration, and properties of the adsorbent were studied. The experimental results are fitted with the Langmuir and Freundlich equations. The adsorption kinetics closely followed the pseudo-second-order model. Thermodynamic parameters (ΔH°, ΔS°, ΔG°) indicate that the adsorption of PDM/ZnO onto AS was feasible, spontaneous, and endothermic. The effects of PDM/ZnO production method and pH value both indicate that electrostatic force may main mechanism in PDM/ZnO adsorption process. The decrease in the adsorption capacity of inactivated sludge suggests that the increase of adsorbent surface area also plays a significant role in the removal process. [ABSTRACT FROM PUBLISHER]