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The adsorption mechanism of the removal of lead from water by using carboxylic functional group (COOH) functionalized on the surface of carbon nanotubes was investigated. Four independent variables including pH, CNTs dosage, contact time, and agitation speed were carried out to determine the influence of these parameters on the adsorption capacity of the lead from water. The morphology of the synthesized multiwall carbon nanotubes (MWCNTs) was characterized by using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) in order to measure the diameter and the length of the CNTs. The diameters of the carbon nanotubes were varied from 20 to 40 nm with average diameter at 24 nm and 10 micrometer in length. Results of the study showed that 100% of lead was removed by using COOH-MCNTs at pH 7, 150 rpm, and 2 hours. These high removal efficiencies were likely attributed to the strong affinity of lead to the physical and chemical properties of the CNTs. The adsorption isotherms plots were well fitted with experimental data.

This study was carried out to evaluate the environmental application of modified and nonmodified carbon nanotubes through the experiment removal of chromium trivalent (III) from water. The aim was to find the optimal condition of the chromium (III) removal from water under different treatment conditions of pH, adsorbent dosage, contact time and agitation speed. Multi wall carbon nanotubes (MW-CNTs) were characterized by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The diameter of the carbon nanotubes produced varied from 20–40 nm with average diameter of 24 nm and 10 micrometer in length. Adsorption isotherms were used to model the adsorption behavior and to calculate the adsorption capacity of the absorbents. The results showed that, 18% of chromium (III) removal was achieved using modified carbon nanotubes (M-CNTs) at pH 7, 150 rpm, and 2 hours for a dosage of 150 mg of CNTs. The removal of Cr (III) is mainly attributed to the affinity of chromium (III) to the physical and chemical properties of the CNTs. The adsorption isotherms plots were well fitted with experimental data.

Graft copolymerization of methyl methacrylate (MMA) onto oil palm empty fruit bunch fiber (OPEFB) was successfully carried out in aqueous medium using hydrogen peroxide as an initiator. Results from the investigation of the optimum conditions for grafting are presented. Maximum percentage of grafting was achieved when the amount of initiator, cocatalyst, and nitric acid were 5.877 ϫ 10 Ϫ3 mol, 2.63 ϫ 10 Ϫ4 mol, and 3.24 ϫ 10 Ϫ3 mol, respectively. The optimum reaction temperature was 50°C and the reaction period was 120 min. The highest percentage of grafting and grafting efficiency were 220 and 47%, respectively, under optimum conditions. The grafted copolymer was characterized by FTIR spectroscopy and scanning electron microscopy. The presence of a band at 1730 cm Ϫ1 provides strong evidence of grafting.

Abstract:A new optical pH sensor based on polysulfone (PSU) and polyaniline (PANI) was developed. A transparent and flexible PSU membrane was employed as a support. The electrically conductive and pH-responsive PANI was deposited onto the membrane surface by in situ chemical oxidative polymerization (COP). The absorption spectra of the PANI-coated PSU membranes exhibited sensitivity to pH changes in the range of 4-12, which allowed for designing a dual wavelength pH optical sensor. The performance of the membranes was assessed by measuring their response starting from high pH and going down to low pH, and vice versa. It was found that it is necessary to precondition the sensor layers before each measurement due to the slight hysteresis observed during forward and backward pH titrations. PSU membranes with polyaniline coating thicknesses in the range of «100-200 nm exhibited fast response times of <4 s, which are attributed to the porous, rough and nanofibrillar morphology of the polyaniline coating. The fabricated pH sensor was characterized by a sigmoidal response (R 2 = 0.997) which allows for pH determination over a wide dynamic range. All membranes were stable for a period of more than six months when stored in 1 M HCl solution. The reproducibility of the fabricated optical pH sensors was found to be <0.02 absorption units after one month storage in 1 M HCl solution. The performance of the optical pH sensor was tested and the obtained pH values were compared with the results obtained using a pH meter device.

Grafted rubberwood fibre was converted to polyamidoxime ion-exchange resin in order to remove heavy metal ions from aqueous solution. The cation-exchange resin existed predominantly in the syn-hydroxyamino form. The water uptake by the resin was ca. 31 g/g dry resin while its hydrogen ion capacity was 3.6 mmol/g. The adsorption capacity of the resin towards different metal ions from wastewater was determined at different pH values within the range 1-6. The prepared chelating ion-exchanger exhibited the highest adsorption capacity towards Cu 2+ ions (3.83 mmol/g), followed by Cd 2+ , Fe 3+ , Pb 2+ , Ni 2+ and Co 3+ ions, respectively. The results showed that the adsorption capacity depended on the solution pH. Polyamidoxime ion-exchange resin was also used to separate Co 3+ and Ni 2+ ions from Cu 2+ ions using a column technique. On passing Cu 2+ /Ni 2+ and Cu 2+ /Co 3+ ion mixtures through the resin at pH 3, Cu 2+ ions were adsorbed by the resin but no sorption of Ni 2+ or Co 3+ ions was detected. Approximately 98% of the Cu 2+ ions could be desorbed from the resin. FT-IR spectroscopy was used to confirm the conversion of polyacrylonitrile-g-rubberwood fibre to polyamidoxime.

Preparation of poly(butyl acrylate)‐grafted oil palm empty fruit bunch fibre (OPEFB) has been successfully carried out using H2O2/Fe2+ as a redox initiator in aqueous solution. The effects of reaction temperature and period, as well as the amount of monomer, initiator and nitric acid, on the percentage of grafting were investigated. The percentage of grafting increases with amount of monomer and can be controlled by setting the appropriate reaction conditions. The maximum percentage of grafting (about 265%) was obtained when the reaction was carried out without acid under optimum conditions (reaction period: 2 h, reaction temperature: 55 °C, amount of H2O2: 5.88 mmol) with 42.2 mmol of monomer. Mechanisms of grafting of butyl acrylate onto OPEFB were proposed. Characterization of the grafted OPEFB was done by Fourier‐transform infrared spectroscopy and scanning electron microscopy. The thermal properties were studied by thermogravimetric analysis. Copyright © 2003 Society of Chemical Industry

Graft copolymerization of poly(methyl acrylate) (PMA) onto rubberwood fiber (RWF) was carried out by free radical initiation. Hydrogen peroxide and ferrous ions were used as an initiator system. Effects of various parameters (reaction temperature and reaction time, as well as hydrogen peroxide, ferrous ammonium sulfate and monomer concentrations) on the grafting percentage were investigated. A high percentage of grafting was achieved when optimum reaction conditions were used. The optimum temperature of the reaction was determined to be about 55 • C and the reaction time was 120 min. The optimum concentration of H 2 O 2 was 0.03 M and the amounts of Fe 2+ and MA were 0.4 mmol and 0.05 mol, respectively. The PMA homopolymer was removed from the graft copolymer by Soxhlet extraction using acetone. The presence of PMA on the fiber was confirmed by FT-IR spectroscopy and gravimetry. The surface morphology of the poly(methyl acrylate)-graft-(rubberwood fiber) was studied by means of scanning electron microscopy.