Synthesis and characterization of guar gum templated hybrid nano silica

Microwave promoted graft copolymerization of poly(ethylacrylate) onto k-carrageenan for removal of Cd and Ni from aqueous solution

Microwave promoted graft copolymerization of poly (ethyl acrylate) onto kappa-carrageenan in presence of a redox pair (ascorbic acid and potassium persulfate) led to the formation of a novel copolymer hydrogel, kappa-carrageenan-graft-poly (ethylacrylate). By varying the reaction conditions such as the microwave power, reaction time, concentration of kappa-carrageenan, ascorbic acid and persulfate, copolymers of highest percentage grafting was obtained and characterized by FT-IR, SEM, TGA and XRD. The copolymer was evaluated as an adsorbent for the adsorption of Ni(II) and Cd(II). Various adsorption parameters such as contact time, pH, initial metal ion concentration, temperature, electrolyte strength and adsorbent dosage were varied to obtain the optimum conditions for the adsorption. The adsorption data for Cd(II), fitted better for Langmuir and Ni(II), fitted much better for Freundlich adsorption isotherm model. Maximum adsorption obtained for cadmium ions and nickel ions was 308.6 mg/g-1 and 305.8 mg/g-1 respectively. The adsorption of both metal ions followed pseudo second order kinetic model. The positive ΔH values endorsed the adsorption process to be endothermic in nature. The negative values of ΔG indicate the spontaneity of the adsorption process while the positive ΔS values showed that the adsorption of metal ions proceeded with increased randomness at the surface of the copolymer. High recovery percentage of the metal ions from the adsorbent indicates that the copolymer can be used for more adsorption cycles.

A novel endo-1,4-β-xylanase from Alicyclobacillus mali FL18: Biochemical characterization and its synergistic action with β-xylosidase in hemicellulose deconstruction

A novel endo-1,4-β-xylanase-encoding gene was identified in Alicyclobacillus mali FL18 and the recombinant protein, named AmXyn, was purified and biochemically characterized. The monomeric enzyme worked optimally at pH 6.6 and 80 °C on beechwood xylan with a specific activity of 440.00 ± 0.02 U/mg and a good catalytic efficiency (kcat/KM = 91.89 s-1mLmg-1). In addition, the enzyme did not display any activity on cellulose, suggesting a possible application in paper biobleaching processes. To develop an enzymatic mixture for xylan degradation, the association between AmXyn and the previously characterized β-xylosidase AmβXyl, deriving from the same microorganism, was assessed. The two enzymes had similar temperature and pH optima and showed the highest degree of synergy when AmXyn and AmβXyl were added sequentially to beechwood xylan, making this mixture cost-competitive and suitable for industrial use. Therefore, this enzymatic cocktail was also employed for the hydrolysis of wheat bran residue. TLC and HPAEC-PAD analyses revealed a high conversion rate to xylose (91.56 %), placing AmXyn and AmβXyl among the most promising biocatalysts for the saccharification of agricultural waste.

Synthesis of porous calcium-guar gum benzoate nano-biohybrids for sorptive removal of congo red and phosphates from water

This work aims to develop an eco-sound nano-bio-hybrid sorbent using sustainable materials for sorptive elimination of congo red and phosphates from aquatic environment. An amphipathic biopolymer derivative, high DS guar gum benzoate (GGBN) was used for entrapment of as synthesized calcium carbonate nanoparticles using solvent diffusion nano-precipitation technique. Designer nano-biohybrids were developed upon experimenting with various materials stoichiometry. SEM, XRD and EDX studies confirmed near-uniform impregnation of rhombohedral calcium carbonate crystals throughout the biopolymer matrix. Average pore size distribution and surface area of final product Ca-GGBNC, were estimated from NDLFT and BET methods respectively. Analysis of adsorption findings acquired at study temperature 27 ± 2 °C showed that the maximum adsorption capacity of Ca-GGBNC recorded qmax, 333.33 mg/g for congo red azo dye and that for phosphate was at 500 mg/g. Adsorptive removal was noted and both components followed pseudo second order kinetics. Intra-particle diffusion kinetics investigation disclosed that the boundary layer effect was prominent and the adsorption rates were not solely directed by the diffusion stage. Activation energy, Ea was to be estimated using Arrhenius equation at 56.136 and 47.015 KJ/mol for congo red and phosphates respectively. The calculated thermodynamic parameters(ΔG°, ΔH°, and ΔS°) revealed the spontaneous, feasible and endothermic sorption process. Owing to active surface area, spherical size, functional moiety and porous network, antibacterial properties of nanobiohybrid were persistent and MIC against E. coli and S. aureus were recorded at 200 μg/mL and 350 μg/mL respectively.

An all-biopolymer self-assembling hydrogel film consisting of chitosan and carboxymethyl guar gum: A novel bio-based composite adsorbent for Cu2+ adsorption from aqueous solution

A novel bio-based composite adsorbent, all biopolymer self-assembled hydrogel film has been prepared by eco-friendly amalgamating chitosan (CS) and carboxymethyl guar gum (CMGG) biopolymers in water without needing small molecules for cross-linking. Various analysis demonstrated the electrostatic interactions and hydrogen bondings within the network structure are responsible for gelling, crosslinking, and forming a 3D structure. Various experimental parameters were optimized to evaluate the CS/CMGG's potential for removing Cu²⁺ ions from aqueous solution, including pH, dosage, Cu(II) initial concentration, contact time, and temperature. The pseudo-second-order kinetic and Langmuir isotherm models are highly correlated with the kinetic and equilibrium isotherm data, respectively. Using the Langmuir isotherm model for an initial metal concentration of 50 mg/L at pH 6.0 and 25 °C, the maximum adsorption of Cu(II) was calculated to be 155.51 mg/g. A combination of adsorption-complexation and ion exchange must be involved in Cu(II) adsorption on the CS/CMGG. Five cycles of the loaded CS/CMGG hydrogel regeneration and reuse were successfully achieved without an appreciable difference in Cu(II) removal percentage. Thermodynamic analysis indicated that copper adsorption occurred spontaneously (ΔG°: -2.85 J/mol, 298 K) and exothermically (ΔH°: -27.58 J/mol). A reusable bio-adsorbent for removing heavy metal ions was developed that is eco-friendly, sustainable, and efficient.

Synthesis and characterization of solid-state Fe-exchanged nano-bentonite and evaluation of methyl orange adsorption

A new adsorbent was synthesized using ion-exchange between iron salts and bentonite modified with acetyl trimethylammonium bromide (CTAB) in the solid phase. Ion-exchange was performed in the solid state at a temperature of 100 °C for 2 min. Various analyses such as X-ray diffraction (XRD), scanning electron microscopy (SEM), porosity measurement (BET), infrared Fourier transform (FT-IR), transmission electron microscopy (TEM), X-ray energy diffraction (EDX), and thermal weighing (TGA) were used to characterize the synthesized nano-adsorbents. Under optimal conditions (pH = 7, time 60 min, concentration of dye solution 150 ppm, and amount of nano-adsorbent 0.75 g/l), the modified nano-adsorbent absorbed 73% of the methyl orange (MO) dye. Adsorption isotherm studies and kinetic model showed that the pseudo-second-order model and Langmuir equation agree with the obtained results. After three reductions of the modified nano-adsorbent in the photo-Fenton process, the dye absorption percentage was 69.50%.

Fabrication and Characterization of Xanthan Gum-cl-poly(acrylamide-co-alginic acid) Hydrogel for Adsorption of Cadmium Ions from Aqueous Medium

The present research demonstrates the facile fabrication of xanthan gum-cl-poly(acrylamide-co-alginic acid) (XG-cl-poly(AAm-co-AA)) hydrogel by employing microwave-assisted copolymerization. Simultaneous copolymerization of acrylamide (AAm) and alginic acid (AA) onto xanthan gum (XG) was carried out. Different samples were fabricated by changing the concentrations of AAm and AA. A sample with maximum swelling percentage was chosen for adsorption experiments. The structural and functional characteristics of synthesized hydrogel were elucidated using diverse characterization tools. Adsorption performance of XG-cl-poly(AAm-co-AA) hydrogel was investigated for the removal of noxious cadmium (Cd(II)) ions using batch adsorption from the aqueous system, various reaction parameters optimized include pH, contact time, temperature, and concentration of Cd(II) ions and temperature. The maximum adsorption was achieved at optimal pH 7, contact time 180 min, temperature 35 °C and cadmium ion centration of 10 mg·L-1. The XG-cl-poly(AAm-co-AA) hydrogel unveiled a very high adsorption potential, and its adsorption capacities considered based on the Langmuir isotherm for Cd(II) ions was 125 mg·g-1 at 35 °C. The Cd(II) ions adsorption data fitted nicely to the Freundlich isotherm and pseudo-first-order model. The reusability investigation demonstrated that hydrogel retained its adsorption capacity even after several uses without significant loss.

Influence of polysiloxane as nanofiller on the surface, optical and thermal properties of guar gum grafted polyaniline matrix

Mesoporous silica containing nanocomposites of in situ polymerised aniline grafted on guar gum (GG), were synthesised by sol-gel technique. Characterization of samples with respect to SEM, TEM, XRD, XPS, FTIR, BET, UV-vis, and PL illustrated the optically active materials with diverse morphologies. Microscopic analysis rendered transitional changes from smooth GG to coated PANI grafts and dense clusters of polysiloxane nanocomposites. FTIR analysis confirmed the interaction of GG-PANI-Si components. XRD diffractograms illustrate tremendous reduction of dominant amorphous phase of GG by grafted HCl doped PANI depicted by characteristic peaks (centred at 2θ=~25° and 2θ=~20.0°) in the partially crystalline and amorphous GG-g-PANI and GG-g-PANI-Si1 nanocomposites. Phase modification through PANI grafting showed specific surface area of GG-g-PANI (7.6m²/g) improving immensely with low polysiloxane contents to ~170.6m²/g in GG-g-PANI-Si1 compared to 25.6m²/g of GG-g-PANI-Si2. The nanocomposites were thermally stable up to ~240°C, each leaving 69% (GG-g-PANI-Si1) and ~77% (GG-g-PANI-Si2) of inorganic residues. Both showed no thermal dedoping, suggesting the good thermal protection offered by polysiloxane layer.

Biomimetic and Bioinspired Synthesis of Nanomaterials/Nanostructures

In recent years, due to its unparalleled advantages, the biomimetic and bioinspired synthesis of nanomaterials/nanostructures has drawn increasing interest and attention. Generally, biomimetic synthesis can be conducted either by mimicking the functions of natural materials/structures or by mimicking the biological processes that organisms employ to produce substances or materials. Biomimetic synthesis is therefore divided here into "functional biomimetic synthesis" and "process biomimetic synthesis". Process biomimetic synthesis is the focus of this review. First, the above two terms are defined and their relationship is discussed. Next different levels of biological processes that can be used for process biomimetic synthesis are compiled. Then the current progress of process biomimetic synthesis is systematically summarized and reviewed from the following five perspectives: i) elementary biomimetic system via biomass templates, ii) high-level biomimetic system via soft/hard-combined films, iii) intelligent biomimetic systems via liquid membranes, iv) living-organism biomimetic systems, and v) macromolecular bioinspired systems. Moreover, for these five biomimetic systems, the synthesis procedures, basic principles, and relationships are discussed, and the challenges that are encountered and directions for further development are considered.