Removal of Pb(II) from water using a bio-composite adsorbent-A systematic approach of optimizing synthesis and process parameters by response surface methodology.

The synthesis parameters for preparing a novel bio-composite adsorbent by integrating a copolymer of 2-hydroxyethyl methacrylate (HEMA), acrylamide (AM) and crosslinker N, N'-methylene bis acrylamide (MBA), polyethylene glycol (PEG) and Azadirachta Indica or Neem leaf (NL) and the process parameters for its subsequent use for adsorption of Pb(II) ion from water were optimized with central composite design (CCD) of response surface methodology (RSM). The structure of the bio-composite was characterized by FTIR, XRD, TGA, DMA, FESEM-EDX and PZC analysis. The optimized adsorbent prepared with a AM: HEMA molar ratio of 5:1, MBA, PEG and NL wt% of 0.75, 4 and 2.5, respectively showed 182.85 mg/g (92.5%) adsorption of Pb(II) from water containing low concentration of 50 mg/L of Pb(II) ion and 911 mg/L (57%) adsorption of the same metal ion for a high feed concentration of 400 mg/L in a solution pH of 6, adsorbent dose of 0.25 g/L and a feed temperature of 30 °C. This functional bio-composite may also be suitably used for separation of other metal ions and polar molecules from water.

Synthesis, characterization and column adsorption properties of gum ghatti and water hyacianth derived cellulose grafted poly(vinyl sulfonic acid-co-acrylamide) composites.

Vinylsulfonic acid (VSA), acrylamide (AM) and N, N methylene bis acrylamide(MBA) were copolymerized by radical polymerization in the presence of gum ghatti (GG) and treated water hyacianth (WH) in water. Several composite copolymers were prepared by varying the i) AM: VSA molar ratios ii) wt% of GG and iii) wt% of treated WH based on a Box-Behnken Design(BBD) of a response surface methodology (RSM) model with three input variables and the batch adsorption capacity (mg/g) of 100 mg/L Cd (II) from water as response. The composite polymer was characterized by Fourier transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis(TGA), X- ray photo electron spectroscopy (XPS), compressive strength, pH reversibility, pH at point zero charge (pHPZC), Brunauer-Emmett-Teller (BET) surface area and scanning electron microscopy (SEM). The network parameters of the composites were determined. The copolymer composite prepared with AM: VSA of 5:1 containing 10 wt% GG and 4 wt% treated WH showed an optimum batch adsorption capacity of 399.15 mg/g Cd (II) from water containing 100 mg/L Cd (II). The same composite showed an adsorption capacity of 170.1 mg/g and a removal% of 31.5 at a feed concentration/feed flow rate/bed height of 150 mgL-1/30mLmin-1/30 mm in a fixed bed column.

Chitosan based nano composite adsorbent-Synthesis, characterization and application for adsorption of binary mixtures of Pb(II) and Cd(II) from water.

Composite type adsorbent was prepared by integrating chitosan (Cs) with crosslinked polymethacrylic acid (PMA) and nano sized halloysite nanotube (HNT). The structure of the resulting Cs-PMA/HNT adsorbents was characterized by FTIR, NMR, XRD, TGA, SEM/EDX and rheological properties. These functional adsorbents were used for removal of Pb(II) and Cd(II) as single and binary competitive mixtures from water. There was a significant improvement in adsorption properties of crosslinked PMA in the presence of Cs and HNT. The effect of synthesis parameters such as wt.% of Cs and HNT on swelling and process parameters such as solution pH, adsorbent dosage, contact time and feed concentration on adsorption of metal ions from water were studied in batch experiments. For a feed concentration of 100mg/L of metal ion, an adsorbent dose of 0.25g/L and a solution pH of 6, the Cs-PMA/HNT composite adsorbent containing 4wt% Cs and 3wt% HNT showed an adsorption capacity (mg/g)/removal% of 357.4/89.4 and 341.6/85.4 for single Pb(II) and Cd(II), respectively which reduced to 313.7/78.4 and 303.6/77.3 for the same metal ions in their binary mixtures in water.

Removal of Cu (II) ion from water using sugar cane bagasse cellulose and gelatin based composite hydrogels.

Several composite hydrogels were prepared by in situ incorporation of sugarcane bagasse cellulose (CB) and a natural polymer gelatin (GT) in to the polyacrylic copolymer network by free radical solution polymerization. The hydrogels were characterized by FTIR, XRD, TGA, DMA, SEM, EDAX, pH at point zero charge and swelling reversibility at varied pH in water. The effects of the synthesis parameters on sorption of Cu (II) from water by the resulting hydrogels were studied and the results were optimized by response surface methodology (RSM) with Box-Behnken design (BBD). The hydrogel prepared with optimized parameters was further studied for sorption of Cu (II) at varied process conditions.

Competitive Removal of Cu(II) and Cd(II) from Water Using a Biocomposite Hydrogel.

With an objective to improve the adsorption properties of a synthetic hydrogel, potato starch (PS) was incorporated in the ter-copolymer (TP) of acrylic acid (AA), acrylamide (AM), and bicarboxylic itaconic acid (IA) during polymerization of the monomers. The resulting TP-PS composite hydrogels were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), nuclear magnetic resonance (NMR), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), and rheological properties. These hydrogels were used for removal of Cu(II) and Cd(II) as single and binary competitive mixtures from water. The effect of PS as well as various physicochemical parameters such as solution pH, adsorbent dosage, contact time of gel with metal ion in water, and concentration of metal ion in water was studied in batch experiments. The adsorption results indicated that the gels could be used as an efficient adsorbent for removal of Cu(II) and Cd(II) from water as single as well as binary mixtures. The TP-PS4 gel containing 4 wt % starch showed a removal % of 85.8 and 77.6 and adsorption capacity (mg/g gel) of 214.5 and 193.9 for Cu(II) and Cd(II), respectively, from water containing 50 mg/L of each of these metal ions in a solution pH of 5.5 and a dose of only 0.2 g/L gel.

Enhanced adsorption of Cr(VI) from water by guar gum based composite hydrogels.

Composite hydrogels were prepared by in situ incorporation of a natural macromolecule guar gum and nano sized bentonite clay in an acrylic network during copolymerization of acrylic acid, N,N-methylenebisacrylamide (MBA) and hydroxyethyl methacrlylate (HEMA) in water. The structure of the hydrogels was characterized and the hydrogels showing the best results in mechanical and swelling properties were used for the removal of low (5-50mg/L) and high (100-800mg/L) concentration of Cr(VI) ions from water. The composite hydrogel showed a high removal of 97.8% (4.89mg/g gel) and 91.4% (182.4mg/g gel) at an initial feed metal ion concentration of 5mg/L and 200mg/L, respectively.

Enhanced adsorption of methyl violet and congo red by using semi and full IPN of polymethacrylic acid and chitosan.

Semi and full interpenetrating polymer network (IPN) type hydrogels were prepared by free radical in situ polymerization of methacrylic acid in presence of chitosan using N,N'-methylene-bis-acrylamide (MBA) and glutaraldehyde (for full IPN) as crosslinker. Several semi and full IPN type hydrogels were prepared by varying initiator and crosslinker concentration and also monomer to chitosan mass ratio. These hydrogels were characterized and used for removal of methyl violet and congo red dye from water. Isotherms and kinetics of dye adsorption were also evaluated.