N.K. Goel

Development of adsorbent from Teflon waste by radiation induced grafting: Equilibrium and kinetic adsorption of dyes

Mutual radiation grafting technique was employed to graft polyacrylic acid (PAA) onto Polytetrafluoroethylene (Teflon) scrap using high energy gamma radiation. Polyacrylic acid-g-Teflon (PAA-g-Teflon) adsorbent was characterized by grafting extent measurement, FTIR spectroscopy, SEM and wet ability & surface energy analysis. The PAA-g-Teflon adsorbent was studied for dye adsorption from aqueous solution of basic dyes, namely, Basic red 29 (BR29) and Basic yellow 11 (BY11). The equilibrium adsorption data were analyzed by Langmuir and Freundlich adsorption isotherm models, whereas, adsorption kinetics was analyzed using pseudo-first order, pseudo-second order and intra-particle diffusion kinetic models. Equilibrium adsorption of BR29 was better explained by Langmuir adsorption model, while that of BY11 by Freundlich adsorption model. The adsorption capacity for BY11 was more than for BR29. Separation factor (R(L)) was found to be in the range 0 < R(L) < 1, indicating favorable adsorption of dyes. Higher coefficient of determination (r(2) > 0.99) and better agreement between the q(e,cal) and q(e,exp) values suggested that pseudo-second order kinetic model better represents the kinetic adsorption data. The non-linearity obtained for intra-particle diffusion plot indicated, more than one process is involved in the adsorption of basic dyes. The desorption studies showed that ~95% of the adsorbed dye could be eluted in suitable eluent.

Cellulose based cationic adsorbent fabricated via radiation grafting process for treatment of dyes waste water.

A cationized adsorbent was prepared from cellulosic cotton fabric waste via a single step-green-radiation grafting process using gamma radiation source, wherein poly[2-(methacryloyloxy) ethyl]trimethylammonium chloride (PMAETC) was covalently attached to cotton cellulose substrate. Radiation grafted (PMAETC-g-cellulose) adsorbent was investigated for removal of acid dyes from aqueous solutions using two model dyes: Acid Blue 25 (AB25) and Acid Blue 74 (AB74). The equilibrium adsorption data was analyzed by Langmuir and Freundlich isotherms, whereas kinetic data was analyzed by pseudo first order, pseudo second order, intra particle diffusion and Boyds models. The PMAETC-g-cellulose adsorbent with 25% grafting yield exhibited equilibrium adsorption capacities of ∼ 540.0mg/g and ∼ 340.0mg/g for AB25 and AB74, respectively. Linear and nonlinear fitting of adsorption data suggested that the equilibrium adsorption process followed Langmuir adsorption isotherm model, whereas, the kinetic adsorption process followed pseudo-second order model. The multi-linearities observed in the intra-particle kinetic plots suggested that the intraparticle diffusion was not the only rate-controlling process in the adsorption of acid dyes on the adsorbent, which was further supported by Boyds model. The adsorbent could be regenerated by eluting the adsorbed dye from the adsorbent and could be repeatedly used.

Electron Beam Grafted Polymer Adsorbent for Removal of Heavy Metal Ion from Aqueous Solution

Abstract An electron beam grafted adsorbent was synthesized by post irradiation grafting of acrylonitrile (AN) on to a non‐woven thermally bonded polypropylene (PP) sheet using 2 MeV electron beam accelerator. The grafted poly(acrylonitrile) chains were chemically modified to convert a nitrile group to an amidoxime (AMO) group, a chelating group responsible for metal ion uptake from an aqueous solution. The effect of various experimental variables viz. dose, dose rate, temperature, and solvent composition on the grafting extent was investigated. PP grafted with the amidoxime group (AMO‐g‐PP) was tested for its suitability as an adsorbent for removal of heavy metal ions such as Co2+, Ni2+, Mn2+, and Cd2+ from aqueous solution. Langmuir and Freundlich adsorption models were used to investigate the type of adsorption of these ions. The adsorption capacities of the adsorbent for the metal ions were found to follow the order Cd2+>Co2+>Ni2+>Mn2+. The kinetics of adsorption of these ions indicated that the rate of adsorption of Cd2+ was faster than that of other ions studied.

Correlation between surface energy and uptake behavior of radiation-grafted methacrylic acid-g-LDPE

An efficient and low-cost effluent adsorbent has been developed by grafting an ionizable monomer onto polyolefin surface and its efficacy was tested for dyes and metal ion uptake from aqueous medium. The grafted matrix was synthesized by optimizing various experimental parameters such as irradiation dose, dose rate, monomer concentration, inhibitor concentration, surfactant concentration, and backbone thickness. Grafting yield decreased with dose rate and thickness and increased with the concentration of methacrylic acid and inhibitor. Grafting kinetics studies indicated that grafting rate is comparatively much affected by dose rate that monomer concentration. Surface energy of the grafted surface was accessed from dynamic contact angle measurements. Uptake study of Basic Red 29, Methylene Blue showed high correlation with grafting yield and polar component of the surface energy; however, metal ion uptake was exceptionally high at ~25 grafting (%), highlighting anomalous behavior of MAA-g-LDPE with respect to surface energy and total ion uptake capacity.

Swelling response of radiation synthesized 2-hydroxyethylmethacrylate-co-[2-(methacryloyloxy)ethyl] trimethylammonium chloride hydrogels under various in vitro conditions.

High-energy 60Co gamma radiation has been used to synthesize 2-hydroxyethylmethacrylate-co-[2-(methacryloyloxy)ethyl]trimethylammonium chloride (HEMA-co-MAETC) polyelectrolyte hydrogels. HEMA-co-MAETC co-polymer gels were characterized and investigated for swelling behaviour in different swelling conditions. Fourier transformed infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) techniques were used to characterize the co-polymer gels. Swelling extent of the gels was found to be a linear function of MAETC content in the gels. The effect of ionic strength, temperature, pH, some solutes of biological importance like glucose, urea, and surfactants such as Triton-X and deoxycholic acid on swelling behavior have been reported. The swelling of gels at higher temperature enhanced the swelling rates but not the swelling extent. HEMA-co-MAETC hydrogel exhibited an excellent responsive characteristic to the ionic strength of the swelling medium. It was found that the swelling of the co-polymer gel at 60°C reduced the swelling–deswelling cycle time by approx. 30% without altering the swelling extent. The gels were also investigated for their swelling in aqueous solutions of anionic dyes, acid blue 25 (AB25), acid blue (AB74) and acid yellow 99 (AY99), and were found to be suitable for dye uptake applications.

Radiation Induced Synthesis of 2‐Hydroxyethyl Methacrylate‐Co‐Vinylbenzyltrimethylammonium Chloride Binary Hydrogel System‐I: Equilibrium Swelling Studies

High‐energy gamma radiation has been used to synthesize 2‐hydroxyethyl methacrylate‐co‐vinylbenzyltrimethylammonium chloride (HEMA‐co‐VBT) hydrogels. Unlike pure poly(vinylbenzyltrimethylammmonium chloride) gels, these gels had good strength and could be handled easily. The equilibrium degree of swelling of the gels was a linear function of the VBT content in the gels. The effect of ionic strength, temperature, pH, some solutes of biological importance such as glucose, urea, and surfactants such as Triton‐X, Deoxycholic acid, have been reported. An increase in temperature of the swelling medium did not affect the EDS but did affect the rate of swelling of the gels. HEMA‐co‐VBT hydrogels showed ionic strength responsive properties, and the reversible swelling‐deswelling action could be performed in NaCl‐water medium for several cycles without losing physical strength of the gel. The gels were also tested for uptake of monovalent anionic dyes namely acid blue 25 (AB25), acid yellow 99 (AY99) from dilute aqueous solutions and found to be suitable for dye uptake with high efficiency.

A horseradish peroxidase immobilized radiation grafted polymer matrix: a biocatalytic system for dye waste water treatment

Horseradish peroxidise (HRP) enzyme, an industrially and environmentally relevant biocatalyst, was covalently immobilized onto epoxy functionalized polypropylene (PP) films, fabricated via 60Co-gamma radiation induced mutual irradiation grafting of 2,3-epoxypropyl methacrylate (EPMA) on to PP matrix. The effect of the grafting parameters, such as radiation dose and monomer concentration, on the grafting yield was studied in order to optimize the radiation grafting process. Poly(EPMA)-g-PP films were characterized by grafting yield determination, FTIR, SEM and XPS. The catalytic activity of the immobilized enzyme HRP system was spectrophotometrically assayed using 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) as a substrate. The immobilized HRP system was investigated for repeatability, storage, thermal and pH stability with respect to the free enzyme. The practical applicability of immobilized HRP in the treatment of textile dye waste water was examined by studying the repeated catalytic degradation of Basic Red 29 (BR29) dye. The immobilized enzyme system was found to cause ∼90% degradation of BR29 over a period of 20 days and was observed to be reusable for five cycles without substantial loss in activity.

Development of Functional Adsorbent From Textile Cotton Waste by Radiation Induced Grafting Process: Equilibrium and Kinetic Studies of Acid Dye Adsorption

An environment benign-aqueous solvent based-single step-radiation induced grafting process was used to graft Poly(vinylbenzyltrimethyl ammonium) chloride (PVBT) onto cellulosic cotton textile waste to transform it into a valuable cationic adsorbent (PVBT-g-Cellulose). The PVBT-g-Cellulose adsorbent was characterized by grafting yield determination, elemental analysis, scanning electron microscope (SEM), and fourier transformed infrared (FTIR) spectroscopy. The PVBT-g-Cellulose adsorbent, investigated for the removal of model dyes from manufactured solutions, exhibited equilibrium adsorption capacities of ∼540 mg/g, ∼474 mg/g, and ∼122 mg/g for acid blue 25(AB25), acid yellow 99(AY99), and acid blue 74(AB74), respectively. The degree of agreement between the adsorption isotherm models and experimental data followed the order: Langmuir-Freundlich>Redlich-Peterson>Langmuir>Freundlich. The kinetic adsorption data was found to be in close agreement with pseudo-second order kinetic model. The elution percentage of as high as ∼95% could be achieved for AB25 using a suitable eluent.

Radiation engineered copper nanoparticles immobilised catalytic reactor (Cu-NICaR) system

A robust and reusable Copper Nanoparticles Immobilised Catalytic Reactor (Cu-NICaR) system was fabricated by immobilising Copper Nanoparticles (Cu NPs) onto a radiation functionalized polymer support. Gamma radiation induced simultaneous irradiation grafting process was employed for introducing poly-glycidyl methacrylate (poly(GMA)) chains onto non woven PE-PP matrix. Optimization of the grafting process was carried out by studying the effect of experimental parameters, such as absorbed dose, monomer concentration and solvent polarity on grafting yield. The poly(GMA)-g-PE-PP matrix was used as a functional polymer support for Cu NPs, synthesised under optimized conditions using NaBH4 as reducing agent. Characterization of the samples was carried out by UV-Visible spectrophotometer, Fourier Transform Infrared (FTIR) Spectroscopy, X-ray fluorescence (XRF), Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM). Catalytic activity of Cu NPs immobilised poly(GMA)-g-PEPP catalytic system was studied by spectrophotometrically monitoring the catalytic reduction of p-nitrophenol (PNP), using NaBH4 as reducing agent. The Cu NPs-immobilised-poly(GMA)-g-PE-PP was observed to exhibit excellent catalytic activity both in batch process (12 cycles over a period of 30 days) as well as in fixed bed column reactor mode, without significant loss of activity. Copyright

Radiolytically Synthesized Noble Metal Nanoparticles: Sensor Applications

Nanotechnology is a discipline that has grown exponentially over the last few decades. The unique properties of nanomaterials, including optical, thermal, electromagnetic etc., make them a highly attractive proposition for a vast array of applications, ranging from medical science to defense technologies. The singular optical properties of noble metal nanoparticles, in particular, have helped develop highly sophisticated sensor systems for estimating trace levels of various analytes. This chapter brings into focus some of the recent developments in the field of sensors based on the Localized Surface Plasmon Resonance (LSPR) properties of Gold (Au) and Silver (Ag) nanoparticles. The use of ionizing radiation, such as 60Co gamma, for fabrication of polymer stabilized Au and Ag nanoparticles via radiolytic route has proved to be one of the most attractive and convenient techniques for nanosynthesis. Using gamma radiation, Au and Ag nanoparticles have been synthesized and successfully employed as LSPR based sensors for estimation of trace levels of analytes such as H2O2, Hg2+, dopamine and Uric Acid. In a nutshell, the chapter highlights how the wedlock between radiation and nanotechnology is fast emerging as a powerful tool to design new materials that can cater to high end applications.