Adsorption of Au(Ⅲ) by amino-modified monodispersed PGMA microspheres and deposition of gold nanoparticles

Monodispersed poly（glycidyl methacrylate）（PGMA） microspheres with various amounts of amino groups（PGMA-NH2） were used to adsorb Au（Ⅲ） from simulated wastewaters. Gold nanoparticle-coated PGMA functional microspheres can be directly obtained via the adsorption process. The adsorption kinetics follows pseudo-second model, and 10 min is enough for reaching at equilibrium. The adsorption isotherm follows Langmuir model, and the adsorption amounts for Au（Ⅲ） are 8.25 and 21.75 mol·kg^-1 at 298 and 328 K, respectively. The relative separation coefficients between Au（Ⅲ）, Pt（Ⅵ）, Pd（Ⅱ）and Co（Ⅱ）, Cu（Ⅱ）; Ni（Ⅱ）, Fe（Ⅲ） are all higher than 100 when 1 〈 pH 〈 3. Furthermore, the characterization analysis of X-ray diffraction（XRD）, thermogravimetrydifferential scanning calorimetry（TG-DSC）, scanning electron microscopy-energy dispersive spectroscopy（SEM-EDS）, transmission electron microscopy（TEM） and Fourier transform infrared spectroscopy（FTIR） confirms that AuCl4^-has been reduced to Au^0 nanoparticles and deposited onto the surface of PGMA-NH2. The current work shows a good prospect for PGMA-NH2 to be a valid adsorbent for the recovery of gold and the possible fabrication of gold nanoparticles by reduction-deposition process without any reductant.

Regeneration performance and carbon consumption of semi-coke and activated coke for SO_2 and NO removal

To decrease the operating cost of flue gas purification technologies based on carbon-based materials, the adsorption and regeneration performance of low-price semi-coke and activated coke were compared for SO2 and NO removal in a simulated flue gas. The functional groups of the two adsorbents before and after regeneration were characterized by a Fourier transform infrared（FTIR） spectrometer, and were quantitatively assessed using temperature programmed desorption（TPD） coupled with FTIR and acid–base titration. The results show that semi-coke had higher adsorption capacity（16.2% for SO2 and 38.6% for NO） than activated coke because of its higher content of basic functional groups and lactones. After regeneration, the adsorption performance of semi-coke decreased because the number of active functional groups decreased and the micropores increased. Semi-coke had better regeneration performance than activated coke. Semi-coke had a larger SO2 recovery of 7.2% and smaller carbon consumption of 12% compared to activated coke. The semi-coke carbon-based adsorbent could be regenerated at lower temperatures to depress the carbon consumption, because the SO2 recovery was only reduced a small amount.

Adsorptive removal of As(Ⅲ) ions from water using spent grain modified by polyacrylamide

In order to enhance the removal efficiency of As（III）, a pre-oxidation process is generally applied first to convert As（III） to As（V）, which may cause unwanted new contaminants. To overcome this problem, efforts were made to develop an effective way to remove As（III）directly without an oxidation step. The effect of polyacrylamide polymers（PAMs） such as anionic PAM, cationic PAM and nonionic PAM, on As（III） ion adsorption by spent grain（SG）was investigated. The physico-chemical properties of the three PAM-polymerized SGs（APSG（anionic PAM-polymerized modified spent grain）, CPSG（cationic PAM-polymerized spent grain） and NPSG（nonionic PAM-polymerized spent grain）） were analyzed using Fourier transform infrared（FT-IR）, scanning electron microscope（SEM） and zeta potential.Batch experimental data showed that the sequence of preferential adsorption for As（III） was APSG 〉 CPSG 〉 NPSG. Active functional groups such as amino group（NH2）, carbonyl group（C_O）, C–N bond of the amide group（CONH2）, and hydroxyl group（O–H） were responsible for As（III） adsorption. Many tubular structures occurring on the surface of APSG possibly increase the specific surface areas and favor the adsorption of As（III） ions. A fixed-bed study was carried out by using APSG as an adsorbent for As（III） from water. Three factors such as bed height, initial concentration and flow rate were studied, and breakthrough curves of As（III） were obtained. The Adams–Bohart model was used to analyze the experimental data and the model parameters were evaluated.