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Abstract

In this study, novel polyacrylonitrile/polystyrene (PAN/PS) blend has been prepared and reinforced with carbon nanoparticle to form polyacrylonitrile/polystyrene/carbon nanoparticle (PAN/PS/CNP) nanocomposite foam. Acid-functional carbon nanoparticle (0.1-3 wt.%) was used as nano-reinforcement for PAN/PS blend matrix. 2’-azobisisobutyronitrile was employed as foaming agent. The PAN/PS/CNP nanocomposite foams have been tested for structure, morphology, mechanical properties, thermal stability, non-flammability, water uptake, and toxic ion removal. Field-emission scanning electron microscopy and transmission electron microscopy exposed unique nanocellular morphology owing to physical interaction between the matrix and functional CNP. PAN/PS/CNP 0.1 Foam with 0.1 wt.% nanofiller had compression strength, modulus, and foam density of 41.8 MPa, 22.3 GPa, and 0.9 mgcm−3, respectively. Nanofiller loading of 3wt.% (PAN/PS/CNP 3 Foam) considerably enhanced the compression strength, modulus, and foam density as 68.2 MPa, 37.7 GPa, and 1.9 mgcm−3, respectively. CNP reinforcement also enhanced the initial weight loss and maximum decomposition temperature of PAN/PS/CNP 3 Foam to 541 and 574 ºC, relative to neat foam (T0 = 411 ºC; T10 = 459 ºC). Nanocomposite foams have also shown excellent flame retardancy as V-0 rating and high char yield of up to 57% were attained. Due to hydrophilic nature of functional carbon nanoparticle, water absorption capacity of 3 wt.% nanocomposite foam was 30% higher than that of pristine foam. Moreover, novel foams were also tested for the removal of toxic Pb2+ ions. PAN/PS/CNP 3 Foam has shown much higher ion removal capacity (166 mg/g) and efficiency (99 %) than that of PAN/PS foam having removal capacity and efficiency of 90 mg/g and 45 %, respectively.

Abstract

Ligand-modified micellar-enhanced ultrafiltration (LM-MEUF) is a membrane technique based on a separation process which can be used for removal of target metals from an aqueous solution. This method involves adding both a metal complexing ligand and surfactant molecule to the aqueous solution under conditions where most of the molecules are present as micelles. This ligand can be attached to the surface of micelles by solubilization and forms the ligand complexes with the metal ion. The aqueous solution is then treated through a membrane which has to be smaller pore sizes than those of the complexes. Hence, permeate water is then purified from the heavy metals. In this study, divalent lead is the target ion in a solution. Filtration experiments were performed with ultrafiltration membrane system, equipped with a regenerated cellulose membrane with a 5000 Daltons cutoff. The pressure was fixed at 4.0 bar with a permeate flow rate of 500 mL min−1. Complexes of Pb2+ ions with three ligands were investigated in micellar medium of different surfactants at different pH values to determine the ligands which could provide separation. Different parameters affecting the percentage rejection of the Pb2+, such as pH and surfactant concentration were also discussed. Results have shown that the maximum percentage of the Pb2+ ions rejection were obtained using sodium dodecyl sulfate (SDS) as a surfactant and dithizone (DZ) as the lead-specific ligand. A waste stream sample from a battery plant was subjected to LM-MEUF process in the optimum conditions determined in this study and it was shown that Pb2+ ions in a waste stream could be removed by LM-MEUF effectively.

Abstract

CS2-modified titanate nanotubes (CS2/TiO2-NTs) are fabricated by reaction of CS2 and Ti-O−Na+ species on titanate nanotubes. Pb2+ ions are coated on the modified nanotubes by ion exchange (Pb/CS2/TiO2-NTs). The products are characterized by means of nitrogen adsorption-desorption isotherms at 77 K (BET method), transmission electron microscopy (TEM), X-ray photoelectron spectrometry (XPS), X-ray diffraction (XRD), atomic absorption spectrometry (AAS), and diffuse reflectance spectroscopy (DRS). The photocatalytic performances of the products are evaluated by monitoring their catalytic activities for degradation of methyl orange under UV light irradiation. The effects of calcination temperature and atmosphere on the photocatalytic performance are investigated. The results reveal that the photocatalytic activities of CS2/TiO2-NTs and Pb/CS2/TiO2-NTs are far higher than that of primary nanotubes, and the optimum calcination temperature is 500 °C under N2 atmosphere. It is also discovered that physically adsorbed Pb2+ ions affect the photocatalytic activity of Pb/CS2/TiO2-NTs obviously. The photocatalytic activity of washed Pb/CS2/TiO2-NTs is higher than that of the unwashed one under the same thermal treatment and reaction conditions.

Biosorption of Pb (II) from aqueous solutions by modified of two kinds of marine algae, Sargassum glaucescens and Gracilaria corticata

In this research, the batch removal of Pb2+ ions from wastewater and aqueous solution with the use o two different modified algae Gracilaria corticata (red algae) and Sargassum glaucescens (brown algae) was examined. The experiment was performed in a batch system and the effect of the pH solution; initial concentration and contact time on biosorption by both biomasses were investigated and compared. When we used S. glaucescens as a biosorbent, the optima conditions of pH, Pb2+ concentration and equilibrium time were at 5, 200 mg/L and 70 min, in the range of 95.6% removal. When G. corticata was used for this process, pH 3, 15 mg/L pb2+ concentration and 50 min contact time, resulted in the maximum removal (86.4%). The equilibrium adsorption data are fitted to the Frundlich and Langmuir isotherm model, by S. glaucescens and G. corticata, respectively. The pb2+ uptake by both biosorbent was best described by the second-order rate model.

.B. & Ariyanto, E. (2007). Competitive adsorption of malachite green and Pb ions on natural zeolite. J. Colloid Interf. Sci. 314, 25–31. DOI: 10.1016/j.jcis.2007.05.032. 40. Kumar, P.S., Vincent, C., Kirthika, K. & Kumar, K.S. (2010). Kinetics and equilibrium studies of Pb 2+ ion removal from aqueous solutions by use of nano-silversol-coated activated carbon. Braz. J. Chem. Eng. 27, 339–346. DOI: 10.1590/S0104-66322010000200012. 41. Ribeiro, J., DaBoit, K., Flores, D., Kronbauer, M.A. & Silva, L.F. (2013). Extensive FE-SEM/EDS, HR-TEM/EDS and ToF-SIMS studies of micron

CCV, Luna AS, Henriques CA. Sorption and desorption of Pb2+ ions by dead Sargassum sp. biomass. Biochem Eng J. 2006;27:310-314. [69] Pahlavanzadeh H, Keshtkar AR, Safdari J, Abadi Z. Biosorption of nickel(II) from aqueous solution by brown algae: Equilibrium, dynamic and thermodynamic studies. J Hazard Mater. 2010;175:304-310. [70] Özer A, Özer D, Ekiz HI. Application of Freundlich and Langmuir models to multistage purification process to remove heavy metal ions by using Schizomeris leibleinii. Process Biochem. 1999;34:919-927. PII: S0032-9592(99)00011-4. [71

the concentration of free Pb 2+ ions below the level required for the precipitation of solid phase Pb(OH) 2 . The formation of nucleation centers through Pb(OH) 2 in the reaction bath is the first step in the growth of PbS film on the substrates. After deposition, the samples were rinsed in deionized water. The non-adherent outer PbS layer was then removed with a cotton swab dipped in a dilute ammonium sulphate solution and again rinsed. A 160 nm thick aluminum (Al) film was used as the bottom contact. It was deposited either by electron beam evaporation or

widely in India, China, Brazil and other parts of the world. It is a multipurpose plant cultivated for phytostabilization and bioenergy production ( 22 ). It has been reported that castor bean can grow luxuriantly in contaminated soils due to its tolerance to heavy metals ( 23 ). Compartmentalization of Pb 2+ ions within the roots and reduced translocation towards shoots is a well-adaptive response of the plants against Pb-toxic conditions ( 24 ). Previous studies reported that castor bean have been used for risk assessment studies of different toxic metals such as Cd