Thermodynamics and kinetics of adsorption of Cu(II) onto waste iron oxide.

This study investigates low-cost sorbents as replacements for current costly methods of removing heavy metals from solution. This investigation explores the waste iron oxide material (F1), which is a by-product of the fluidized-bed reactor (FBR)-Fenton reaction, for use in the treatment of the wastewater in Taiwan. X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the F1. In this investigation, F1 are tested as adsorbents for removing copper (Cu(2+)) from aqueous solutions. The highest Cu(2+) adsorption capacity of F1 adsorbent was determined as 0.21 mmolg(-1) for 0.8 mmoldm(-3) initial Cu(2+) concentration at pH 6.0 and 300 K. Adsorption data were well described by the Freundlich model and the thermodynamic constants of the adsorption process, DeltaG degrees , DeltaH degrees and DeltaS degrees were evaluated as -6.12 kJmol(-1) (at 318 K), 9.2 kJmol(-1) and 48.19 Jmol(-1)K(-1) (at 318 K), respectively. Additionally, a pseudo-second-order rate model was adopted to describe the kinetics of adsorption.

Polypropylene fibers modified by plasma treatment for preparation of Ag nanoparticles.

A novel method for preparing poly(propylene-graft-2-methacrylic acid 3-(bis-carboxymethylamino)-2-hydroxy-propyl ester)-silver fibers (PPG-IAg fibers) by plasma-induced grafting polymerization is presented in this study. The chelating groups, -N(CH2COO-)2 (GMA-IDA), on the surface of the PPG-I fibers are the coordination sites for chelating silver ions. At these sites, Ag nanoparticles were grown first by reduction with UV light with a wavelength of 366 nm, and second, through immersion in a 24% formaldehyde solution with pH values set variously at 2, 5, 8, and 11. The characteristics of the PPG-I fibers with differing durations of plasma treatment were monitored by using a Fourier transform infrared (FT-IR) spectroscope. Scanning electronic microscopy (SEM) and elemental analysis show that the percentage of GMA-IDA grafted onto PP fiber reaches a maximum when the plasma treatment time is 3 min. Plasma treatment time beyond a certain length of time results in an abundance of free radicals and causes considerable cross-linking on the fiber surface which thus decreases the extent of grafting. Moreover, the crystalline phase of Ag nanoparticles is identified by using X-ray diffraction (XRD). When the PPG-I fibers are reduced by the UV light method, SEM and TEM microscopes reveal that the size of the Ag nanoparticles on the fiber surface decreases significantly with the increase of pH values in aqueous solutions. Notably, in the reduction of formaldehyde solution, the particle size of Ag nanoparticles reaches a minimum at the lowest pH value. The TEM observations show that Ag nanoparticles are distributed both in the exterior and interior of the grafting layer. In addition, under high pH values the distribution of the Ag nanoparticles permeate more deeply in the GMA-IDA grafting layer due to the swelling effect of the GMA-IDA polymer.

Modification of polypropylene fibers by plasma and preparation of hybrid luminescent and rodlike CdS nanocrystals/polypropylene fibers.

A simple method for the preparation of hybrid luminescence and rodlike CdS nanoclusters/poly (propylene-grafted-(2-methylacrylic acid 3-(bis-carboxymethyl amino-2-hydroxy-propyl ester) (GMA-IDA fibers, by plasma induced method following chemical deposition method, is presented in this study. GMA-IDA chelating groups which are grafted onto the poly(propylene) fibers are the coordination sites for chelating Cd+2, on which nano-sized CdS nanocrystals grew. TEM observations demonstrate that the mean diameter of CdS nanocrystals inside the poly(PP-graft-GMA-IDA) fibers alters from 2 nm to 8 nm at various concentrations of S2- solution. Additionally, SEM presents that the CdS nanocrystals on the surface have rod-like structure. The UV-vis absorption spectra provide the information of the absorption edges, band-gaps, and average diameter of CdS nanocrystals, the results of which are coincidence with the TEM observations. Furthermore, the photoluminescence (PL) shows the maximum peaks are 495 nm, 571 nm, 657 nm, and 675 nm corresponding to the mean particle sizes 2.6 nm, 3.5 nm, 4.8 nm, and 7.7 nm, respectively, at an excitation wavelength of 366 nm.

Recovery of Acinetobacter radioresistens lipase by hydrophobic adsorption to n-hexadecane coated on nonwoven fabric.

A simple and clean adsorption/desorption process was proposed for recovering Acinetobacter radioresistens lipase from fermentation broth. The adsorbent used was n-hexadecane coated on a hydrophobic nonwoven fabric (NWF). n-Hexadecane has a melting point of 16-18 degrees C, and its affinity for lipase decreases markedly from liquid to solid state. Accordingly, performing the adsorption and desorption above and below, respectively, the melting point would need no extraneous materials for separation. The adsorption isotherms at various temperatures were found to follow the Langmuir model. Simulation of the batch adsorption/desorption process showed that there exists an optimal amount of adsorbent for both concentration factor and enzyme recovery; the process is restrained by equilibrium. The performance of column adsorption/desorption could also be simulated using the adsorption isotherm, and it was shown that the concentration factor was proportional to the amount of adsorbent used. The benefits of this process include easy preparation of adsorbent, low operational cost, no extraneous materials needed, negligible enzyme denaturation, high efficiency, and simple process simulation.