P-nitrophenol adsorption on polystyrene-co-divinylbenzene functionalized copolymers

The removal of phenolic compounds form wastewater is of significant importance due to the damages caused to the environment and human life [1-3]. The polymeric adsorbents were intense studied in the adsorption processes and are now considered efficient in the removal of different pollutants from wastewater, including phenolic compounds [4-6]. In this study we introduce two new polystyrene-co-divinylbenzene copolymers, functionalized with carboxylic groups. The two copolymers, PC12 (with 12% divinylbenzene) and PC6.7 (with 6.7% divinylbenzene) were characterized and tested as adsorbents for the removal of p-nitrophenol from aqueous solution. The effect of different parameters on the removal efficiency was investigated. The kinetics and adsorption isotherm were also evaluated. The copolymers were characterized by means of IR spectroscopy. FTIR spectra were carried out using a Shimadzu Prestige-21 spectrometer in the range 400–4000 cm-1, using KBr pellets and resolution of 4 cm-1. N2 adsorption–desorption isotherms of copolymers were performed on Micromeritics ASAP 2020 instrument. The specific surface area was calculated using the Brunauer–Emmett–Teller (BET) method and the pore size distribution using the Barrett–Joyner–Halenda(BJH) method from the desorption curves. Thermal analysis (TG/DSC) was carried out using a NETZSCH-STA 449C instrument. The curves were recorded in the range of 25–1200 °C with a heating rate of 10 K min-1, using platinum crucibles. The experiments were carried out in artificial air at a flow rate of 20 mL min-1. The morphology of the nanopowders was investigating by scanning electron microscopy (SEM), using a FEI Quanta FEG 250 microscope. The adsorption experiments were performed at 25 °C, using 50 mg adsorbent added at 25 mL p-nitrophenol solution with initial concentrations of 100 mg L-1. All experiments were performed at a 200 rpm shaking speed for 8 h to ensure the equilibrium of the adsorption process. The p-nitrophenol concentration was monitored by spectrophotometric analysis using a Schimadzu UV–VIS Spectrophotometer. The absorbance values were measured according to the maximum UV-absorption, at the wavelength of 316 nm. The copolymers proved a good adsorption capacity. The removal efficiency of pnitrophenol using PC6.7 adsorbent was 86% while using PC12 was 78%. The experimental data were fitted with Langmuir, Freundlich, Redlich-Peterson and Sips isotherms. The maximum adsorption capacity of p-nitrophenol, resulted from Langmuir isotherm was 213.4 mg g-1 using PC6.7 adsorbent and 80.8 mg g-1 using PC12

Silica-Coated Magnetic Nanocomposites for Pb2+ Removal from Aqueous Solution

Magnetic iron oxide-silica shell nanocomposites with different iron oxide/silica ratio were synthesized and structurally characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), small-angle neutron scattering, magnetic and N2-sorption studies. The composite that resulted with the best properties in terms of contact surface area and saturation of magnetization was selected for Pb2+ adsorption studies from aqueous media. The material presented good absorption capacit (maximum adsorption capacity 14.9 mg·g−1) comparable with similar materials presented in literature. Its chemico-physical stability and adsorption capacity recommend the nanocomposite as a cheap adsorbent material for lead

IL-Functionalized Mg₃Al-LDH as New Efficient Adsorbent for Pd Recovery from Aqueous Solutions

Palladium is a noble metal of the platinum group metals (PGMs) with a high value and major industrial applications. Due to the scarce palladium resources, researchers’ attention is currently focused on Pd ions recovery from secondary sources. Regarding the recovery process from aqueous solutions, many methods were studied, amongst which adsorption process gained a special attention due to its clear advantages. Moreover, the efficiency and the selectivity of an adsorbent material can be further improved by functionalization of various solid supports. In this context, the present work aims at the synthesis and characterization of Mg3Al-LDH and its functionalization with ionic liquid (IL) (Methyltrialkylammonium chloride) to obtain adsorbent materials with high efficiency in Pd removal from aqueous solutions. The maximum adsorption capacity developed by Mg3Al-LDH is 142.9 mg Pd., and depending on the functionalization method used (sonication and co-synthesis, respectively) the maximum adsorption capacity increases considerably, qmax-Mg3Al IL-US = 227.3 mg/g and qmax-Mg3Al IL-COS = 277.8 mg/g

Combustion Synthesis of SrAl₂O₄: Eu²⁺, Dy³⁺ Phosphorescent Pigments for Glow-in-the-Dark Safety Markings

This study deals with SrAl2O4: Eu2+, Dy3+ phosphor pigments prepared by an optimized perchlorate-assisted combustion synthesis and tested for developing glow-in-the-dark safety markings. Recipes with different oxidizer/fuel ratios were designed to create an in-situ reducing-reaction atmosphere and promote Eu3+ → Eu2+ reduction, which is responsible for the specific long-lasting, green emission of the pigments. The obtained data proved the efficiency of glycine-rich mixtures (up to 200% glycine excess), which led to improved optical features, as compared to the reference stoichiometric sample. The best results in terms of emission intensity and decay time were obtained in the case of 100% glycine excess. The sample with optimum emission characteristics was successfully tested in making glow-in-the-dark coatings applied to two different substrates and using pigment concentrations between 10 and 33% weight

Combustion Synthesis of SrAl2O4: Eu2+, Dy3+ Phosphorescent Pigments for Glow-in-the-Dark Safety Markings

This study deals with SrAl2O4: Eu2+, Dy3+ phosphor pigments prepared by an optimized perchlorate-assisted combustion synthesis and tested for developing glow-in-the-dark safety markings. Recipes with different oxidizer/fuel ratios were designed to create an in-situ reducing-reaction atmosphere and promote Eu3+ → Eu2+ reduction, which is responsible for the specific long-lasting, green emission of the pigments. The obtained data proved the efficiency of glycine-rich mixtures (up to 200% glycine excess), which led to improved optical features, as compared to the reference stoichiometric sample. The best results in terms of emission intensity and decay time were obtained in the case of 100% glycine excess. The sample with optimum emission characteristics was successfully tested in making glow-in-the-dark coatings applied to two different substrates and using pigment concentrations between 10 and 33% weight

Ni-Ti co-doped hibonite ceramic pigments by combustion synthesis: crystal structure and optical properties

Hibonite (CaAl12O19, space group P63/mmc) has structural formula A[XII]M1[VI] M2[V]M32[IV]M42[VI]M56[VI]O19 where Ca is 12-fold coordinated at site A and Al3+ ions are dis-tributed over five different sites: 3 distinct octahedra [M1 (D3d), M4 (C3v) and M5 (Cs)], the M3 tetrahedron (C3v), and the unusual 5-fold coordinated trigonal bipyramid M2 (D3h); (Bermanec et al., 1996; Nagashima et al., 2010). Hibonite is able to accommodate a wide range of ions with different valence and coordina-tion, making its structure a promising ceramic pigment. One of the main challenges is to under-stand and control incorporation mechanisms and the threshold of chromophores solubility. It is known that M2+ ions tend to be hosted at the M3 site, while M4+ ions are preferentially accommodated at the M4 site: the introduction of divalent ions might be promoted by the associated incorporation of tetravalent cations, which ensure the lattice electroneutrality and are ordered over the M4 face-sharing octahedral dimers. In this work, the mechanism of the coupled substitution 2Al3+ → (Ni2+ + Ti4+) was investi-gated by combining X-ray powder diffraction and diffuse reflectance spectroscopy techniques. Hibonite turquoise pigments with increasing Ni + Ti doping (CaAl12‒2xNixTixO19, where x = 0.1‒2.0 apfu) were prepared by combustion synthesis, utilizing fuel mixtures (urea, glycine, -alanine) set up according to their compatibility with metal nitrates used as raw materials. The ignition temperature of combustion reaction was 400 ºC, but samples underwent an additional annealing at 1200 ºC. Samples up to x = 0.4 are monophasic; for higher doping, hibonite is the main component accompanied to growing percentages of spinel and perovskite associated phases. The Ni and Ti addition induced a regular increasing of the hibonite unit-cell parameters till x = 1.0, that is proportional to the amount and difference in ionic radii of dopants. In particular, an elongation of the MO bond distances of both M3 and M4 sites was observed. In terms of optical parameters, Ni2+ is preferentially incorporated in tetrahedral coordination, up to 0.3 apfu at the M3 site, and at the M4 octahedron as well (up to 0.19 apfu). The crystal field strength of fourfold coordinated Ni2+ is regularly decreasing, implying an elongation of the local NiO bond that is consistent with the volume increasing from AlO4 to NiO4 tetrahedra registered by XRD. Ti4+ ions are accommodated at both the M2 and M4 octahedra which expand proportionally to the amount of dopants. Pigment purity and colour strength vary with doping depending on the multistep mechanism of Ni and Ti incorporation in the hibonite lattice. References Bermanec V., Holtstam D., Sturman D., Criddle A. J., Back M. E. and Šćavničar S. (1996) - Nežilovite, a new member of the magnetoplumbite group, and the crystal chemistry of magnetoplumbite and hibonite. Canadian Mineralogist, 34, 1287-1297. Nagashima M., Armbruster T. and Hainschwang T. (2010) - A temperature-dependent structure study of gem-quality hibonite from Myanmar. Mineralogical Magazine, 74, 871-885