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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 concentr...

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 ...

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.

Polyaniline adsorbent prepared by chemical oxidation was developed to remove the humic acid (HA) in aqueous solution. The adsorbents showed the high adsorption capacity for aqueous HA with the maximum adsorption amount 126.58 mg g−1, and the adsorption isotherm obeyed the Langmuir model. The adsorption kinetics followed an initial diffusion-controlled and then an attachment-controlled adsorption process. The HA adsorption was not much impacted in the presence of Na+, K+, while Ca2+ ion in aqueous solution can evidently enhance the HA adsorption. The HA adsorption on polyaniline decreased with increasing solution pH owing to the electrostatic interaction between imine and amine of polyaniline and disassociated HA. The HA molecules adsorbed on the polyaniline can be effectively desorbed in 0.1 M NaOH solution, and regenerated adsorbent can be repeatedly used in the subsequently adsorption–regeneration cycles.