Production and characterization of cellulose nanofibril (CNF) from agricultural waste corn stover.

Agricultural waste corn stover has little economic value. Cellulose was extracted from corn stover by the processes of alkali treatment and delignification, resulting in a > 93% purity. The particle size of the extracted cellulose was reduced by mechanical shearing through high pressure homogenization. When passing through a homogenizer thirty times, the cellulose nanofibril (CNF) can be obtained. The diameters of the CNF ranged between 5 and 50 nm, and the lengths were microns. The mechanical properties of the films, made by corn stover cellulose, with and without high pressure homogenization shearing were evaluated using an Instron instrument. The films made by cellulose without shearing exhibited weaker mechanical properties, while the CNF films exhibited stronger mechanical properties. The linear rheological properties of CNF suspensions were also investigated and results show solid-like viscoelastic behavior. Our findings regarding corn stover CNF are similar to those CNF from other sources reported in the literature.

Improved hydroxypropyl methylcellulose (HPMC) films through incorporation of amylose-sodium palmitate inclusion complexes.

Polymer film blends of hydroxypropyl methylcellulose (HPMC) and amylose-sodium palmitate inclusion complexes (Na-Palm) were produced with no plasticizer, and were observed to have improved physical and gas barrier properties as compared with pure HPMC. The crystalline amylose helices incorporating the hydrophobic sodium palmitate ligand decreased the water vapor permeability of a 50/50% blended film of HPMC/Na-Palm by 40% and decreased oxygen permeability by 96%. The incorporation of 25% Na-Palm into HPMC films resulted in improved elongation, Young's modulus and toughness. Addition of the amylose-complexes produced relatively smooth, high clarity films which had reduced solubility in neutral and acidic solutions. Increasing concentrations of Na-Palm increased film thermal resilience and increased storage modulus at high temperatures. The heat deflection temperature of the films also increased with increasing concentrations of amylose-complex; HPMC/Na-Palm film blends with >50% Na-Palm displayed almost no material deformation up to 250 °C.

Metals Bioaccumulation Mechanism in Neem Bark.

The aim of this work was to define the bioaccumulation mechanism of metals onto the non-living biomaterial prepared from an extensively available plant bark biomass of neem (Azadirachta indica). Based on maximum ultimate fixation capacities (mmol/g) of the product, metals ions could be arranged as Hg(2+) < Cd(2+) < Pb(2+) ≅ Cu(2+). Surface properties of the biomaterial were characterized by X-ray photoelectron spectroscopy and X-ray diffraction techniques for their sorption mechanism. Whewellite (C2CaO4 · H2O) was identified in the biomaterial, which indicated that calcium ions are electrovalently bonded with carboxylate ions facilitating the ion exchange mechanism with metal ions. Bioaccumulation of metal ions was also studied by Fourier transform infrared spectroscopy, which indicated the presence of functional groups implicated in adsorbing metal ions. Biomaterial did not adsorb anionic As(III), As(V) and Cr(VI), because of their electrostatic repulsion with carboxylic functional groups. Neem bark can be used as bioindicators, bioaccumulators and biomonitors while determining environmental pressures. Metal bioaccumulative properties and structural investigation of plant bark has potential in providing quantitative information on the metal contamination in the surrounding environment.

Sorption of triazine and organophosphorus pesticides on soil and biochar.

Sorption and degradation are the primary processes controlling the efficacy and runoff contamination risk of agrochemicals. Considering the longevity of biochar in agroecosystems, biochar soil amendment must be carefully evaluated on the basis of the target agrochemical and soil types to achieve agricultural (minimum impact on efficacy) and environmental (minimum runoff contamination) benefits. In this study, sorption-desorption isotherms and kinetics of triazine (deisopropylatrazine) and organophosphorus (malathion, parathion, and diazinon) pesticides were first investigated on various soil types ranging from clayey, acidic Puerto Rican forest soil (PR) to heavy metal contaminated small arms range (SAR) soils of sandy and peaty nature. On PR, malathion sorption did not reach equilibrium during the 3 week study. Comparison of solution-phase molar phosphorus and agrochemical concentrations suggested that degradation products of organophosphorus pesticides were bound on soil surfaces. The degree of sorption on different soils showed the following increasing trend: deisopropylatrazine < malathion < diazinon < parathion. While sorption of deisopropylatrazine on SAR soils was not affected by diazinon or malathion, deisopropylatrazine suppressed the sorption of diazinon and malathion. Deisopropylatrazine irreversibly sorbed on biochars, and greater sorption was observed with higher Brunauer-Emmett-Teller surface area of biochar (4.7-2061 mg g(-1)). The results suggested the utility of biochar for remediation of sites where concentrations of highly stable and mobile agrochemicals exceed the water-quality benchmarks.

The production of oxygenated polycrystalline graphene by one-step ethanol-chemical vapor deposition.

Large-area mono- and bilayer graphene films were synthesized on Cu foil (~ 1 inch(2)) in about 1 min by a simple ethanol-chemical vapor deposition (CVD) technique. Raman spectroscopy and high resolution transmission electron microscopy revealed the synthesized graphene films to have polycrystalline structures with 2-5 nm individual crystallite size which is a function of temperature up to 1000°C. X-ray photoelectron spectroscopy investigations showed about 3 atomic% carboxylic (COOH) functional groups were formed during growth. The field-effect transistor devices fabricated using polycrystalline graphene as conducting channel (L(c)=10 µm; W(c)=50 µm) demonstrated a p-type semiconducting behavior with high drive current and Dirac point at ~35 V. This simple one-step method of growing large area polycrystalline graphene films with semiconductor properties and easily functionalizable groups should assist in the realization of potential of polycrystalline graphene for nanoelectronics, sensors and energy storage devices.

2,4,6-triamino-1,3,5-trinitrobenzene (TATB) and TATB-based formulations--a review.

This paper reviews the research and development work on 2,4,6-triamino-1,3,5-trinitrobenzene (TATB), and TATB-based formulations of other explosives. Syntheses including the production of nano-sized particles, analytical methods, thermophysical properties, performance, formulations, toxicity and safety of TATB are reviewed in this work.

Competitive adsorption of Cu (II), Co (II) and Ni (II) from their binary and tertiary aqueous solutions using chitosan-coated perlite beads as biosorbent.

A new composite chitosan-coated biosorbent was prepared and was used for the removal and recovery of heavy metals from aqueous solution. In the present investigation, equilibrium adsorption characteristics of Cu (II), Ni (II), and Co (II) from their binary and tertiary solution on newly developed biosorbent chitosan-coated perlite beads were evaluated through batch and column studies. These beads were characterized by using FTIR, EDXRF and surface area analysis techniques. The effect of various biosorption parameters like effect of pH, agitation time, concentration of adsorbate and amount of adsorbent on extent of adsorption was investigated. The adsorption follows Lagergren first order kinetic model. The equilibrium adsorption data were fitted to Freundlich and Langmuir adsorption isotherm models and the model parameters were evaluated. Both the models represent the experimental data satisfactorily. The sorbent loaded with metal was regenerated with 0.1N NaOH solution. Furthermore the column dynamic studies indicate the re-usage of the biosorbent.

Adsorptive removal of copper and nickel ions from water using chitosan coated PVC beads.

A new biosorbent was developed by coating chitosan, a naturally and abundantly available biopolymer, on to polyvinyl chloride (PVC) beads. The biosorbent was characterized by FTIR spectra, porosity and surface area analyses. Equilibrium and column flow adsorption characteristics of copper(II) and nickel(II) ions on the biosorbent were studied. The effect of pH, agitation time, concentration of adsorbate and amount of adsorbent on the extent of adsorption was investigated. The experimental data were fitted to Langmuir and Freundlich adsorption isotherms. The data were analyzed on the basis of Lagergren pseudo first order, pseudo-second order and Weber-Morris intraparticle diffusion models. The maximum monolayer adsorption capacity of chitosan coated PVC sorbent as obtained from Langmuir adsorption isotherm was found to be 87.9 mg g(-1) for Cu(II) and 120.5 mg g(-1) for Ni(II) ions, respectively. In addition, breakthrough curves were obtained from column flow experiments. The experimental results demonstrated that chitosan coated PVC beads could be used for the removal of Cu(II) and Ni(II) ions from aqueous medium through adsorption.

Fixation of heavy metals onto lignocellulosic sorbent prepared from paddy straw.

The sorption behavior of biosorbent prepared from paddy straw with nine different heavy metals has been studied. The binding mechanisms involving adsorption and the cation-exchange process have also been investigated. Characterization of biosorbent through a scanning electron microscope revealed no major surface deformity resulting from the chemical treatment. X-ray photo electron spectroscopy was also used to determine the presence of exchangeable cations in the sorbent and the speciation of bound chromium, cadmium, and mercury. The maximum sorption capacity (millimoles/gram) obtained from the Langmuir model for Pb2+, Cd2+, Hg2+, Co2+, Ni2+, Mn2+, Zn2+, and Cu2+ were 0.286, 0.147, 0.226, 0.181, 0.196, 0.189, 0.219, and 0.248, respectively. Interpretation of Dahlquist (1978) and Scatchard (1949) was also used for the binding site heterogeneity. The unique ability of the biosorbent to bind nine different metals has been attributed to the presence of surface heterogeneity and Ca2+ ions, which attract and sequester metal ions. Biosorption results are useful for the development of low-cost biosorbent.

Physicochemical properties of an insensitive munitions compound, N-methyl-4-nitroaniline (MNA).

Accurate information on physicochemical properties of an organic contaminant is essential for predicting its environmental impact and fate. These properties also provide invaluable information for the overall understanding of environmental distribution, biotransformation, and potential treatment processes. In this study the aqueous solubility (Sw), octanol-water partition coefficient (Kow), and Henry's law constant (K(H)) were determined for an insensitive munitions (IM) compound, N-methyl-4-nitroaniline (MNA), at 298.15, 308.15, and 318.15 K. Effect of ionic strength on solubility, using electrolytes such as NaCl and CaCl2, was also studied. The data on the physicochemical parameters were correlated using the standard Van't Hoff equation. All three properties exhibited a linear relationship with reciprocal temperature. The enthalpy and entropy of phase transfer were derived from the experimental data.

Biosorption mechanism of nine different heavy metals onto biomatrix from rice husk.

A biomatrix was prepared from rice husk, a lignocellulosic waste from agro-industry, for the removal of several heavy metals as a function of pH and metal concentrations in single and mixed solutions. The biomatrix was characterized using scanning electron microscope and Fourier transform infrared spectroscopy, which indicated the presence of several functional groups for binding metal ions. Different experimental approaches were applied to show mechanistic aspects, especially the role of calcium and magnesium present in the biomatrix in ion exchange mechanism. The ultimate maximum adsorption capacity obtained from the Langmuir isotherm increases in the order (mmol/g): Ni (0.094), Zn (0.124), Cd (0.149), Mn (0.151), Co (0.162), Cu (0.172), Hg (0.18) and Pb (0.28). The sorption of Cr(III) onto biomatrix at pH 2 was 1.0 mmol/g. Speciation of chromium, cadmium and mercury loaded on the biomatrix was determined by X-ray photoelectron spectroscopy. The biomatrix has adsorption capacity comparable or greater to other reported sorbents.

Removal of arsenic (III) and arsenic (V) from aqueous medium using chitosan-coated biosorbent.

A biosorbent was prepared by coating ceramic alumina with the natural biopolymer, chitosan, using a dip-coating process. Removal of arsenic (III) (As(III)) and arsenic (V) (As(V)) was studied through adsorption on the biosorbent at pH 4.0 under equilibrium and dynamic conditions. The equilibrium adsorption data were fitted to Langmuir, Freundlich, and Redlich-Peterson adsorption models, and the model parameters were evaluated. All three models represented the experimental data well. The monolayer adsorption capacity of the sorbent, as obtained from the Langmuir isotherm, is 56.50 and 96.46 mg/g of chitosan for As(III) and As(V), respectively. The difference in adsorption capacity for As(III) and As(V) was explained on the basis of speciation of arsenic at pH 4.0. Column adsorption results indicated that no arsenic was found in the effluent solution up to about 40 and 120 bed volumes of As(III) and As(V), respectively. Sodium hydroxide solution (0.1M) was found to be capable of regenerating the column bed.

Dispersion of chitosan on perlite for enhancement of copper(II) adsorption capacity.

Chitosan coated perlite beads were prepared by drop-wise addition of slurry, made of chitosan dissolved in oxalic acid and perlite, to an alkaline bath (0.7 M NaOH). The beads that contained 32% chitosan enhanced the accessibility of OH and amine groups present in chitosan for adsorption of copper ions. The experiments using Cu(II) ions were carried out in the concentration range of 50-4100 mg/L (0.78-64.1 mmol/L). Adsorption capacity for Cu(II) was pH dependent and a maximum uptake of 104 mg/g of beads (325 mg/g of chitosan) was obtained at pH 4.5 when its equilibrium concentration in the solution was 812.5 mg/L at 298 K. The XPS and TEM data suggested that copper was mainly adsorbed as Cu(II) and was attached to amine groups. The adsorption data could be fitted to one-site Langmuir adsorption model. Anions in the solution had minimal effect on Cu(II) adsorption by chitosan coated perlite beads. EDTA was used effectively for the regeneration of the bed. The diffusion coefficient of Cu(II) onto chitosan coated beads was calculated from the breakthrough curve and was found to be 2.02 x 10(-8) cm(2)/s.

Removal of hexavalent chromium from wastewater using a new composite chitosan biosorbent.

A new composite chitosan biosorbent was prepared by coating chitosan, a glucosamine biopolymer, onto ceramic alumina. The composite bioadsorbent was characterized by high-temperature pyrolysis, porosimetry, scanning electron microscopy, and X-ray photoelectron spectroscopy. Batch isothermal equilibrium and continuous column adsorption experiments were conducted at 25 degrees C to evaluate the biosorbent for the removal of hexavalent chromium from synthetic as well as field samples obtained from chrome plating facilities. The effect of pH, sulfate, and chloride ion on adsorption was also investigated. The biosorbent loaded with Cr(VI) was regenerated using 0.1 M sodium hydroxide solution. A comparison of the results of the present investigation with those reported in the literature showed that chitosan coated on alumina exhibits greater adsorption capacity for chromium(VI). Further, experimental equilibrium data were fitted to Langmuir and Freundlich adsorption isotherms, and values of the parameters of the isotherms are reported. The ultimate capacity obtained from the Langmuir model is 153.85 mg/g chitosan.