scholarly journals Breakthrough and thermodynamic adsorption of Cr (VI) y Ni (II) bioadsorption in continuous system

2021 ◽  
Vol 26 (1) ◽  
pp. 72-81
Author(s):  
Candelaria Nahir Tejada Tovar ◽  
Luis Carlos Newball López ◽  
Camilo Esteban Cardona Lara
Keyword(s):  
Room Temperature ◽  
Continuous System ◽  
Packed Bed ◽  
Hydroxyl Groups ◽  
Heterogeneous Structure ◽  
Active Centers ◽  
Chromium Vi ◽  
Removal Of Heavy Metals ◽  
Useful Life ◽  
Mutagenic Effects

The removal of heavy metals present in water is an issue of environmental interest, due to bioaccumulation, biomagnification and the carcinogenic and mutagenic effects on living beings. The objective of the present study was to use plantain peel residues in Chromium (VI) and Nickel (II) removal in continuous system, evaluating the effect of bedheight, temperature and adsorbent particle size on the process; obtaining a 98.7% 99.71% removal yield for Cr (VI) and Ni(II), respectively. The FTIR showed that the bioadsorbent has a heterogeneous structure with the presence of hydroxyl groups, saturated and unsaturated hydrocarbons, carbonyls, carboxyl, among others, and it was established that the process is controlled by electrostatic reactions between the active centers and the metal. The breaka ge curve was carried out under the optimal conditions established by the Response Surface Methodology (RSM) and it was established that the bioadsorbent has an extensive useful life, as it was not saturated throughout the process. The hermodynamic parameters established that the process is exothermic and irreversible, being favored at room temperature. Taking into account the behavior of plantain peels during the breakage curve, it is recommended to use it as a filler in a packed bed to remove Cr (VI) and Ni (II).

scholarly journals Cr(VI) biosorption: Effect of temperature, particle size and bed height

2020 ◽  
pp. 78-86
Author(s):  
Candelaria Nahir Tejada-Tovar ◽  
Angel Villabona-Ortíz ◽  
Rodrigo Ortega Toro
Keyword(s):  
Particle Size ◽  
Fourier Transforms ◽  
Continuous System ◽  
Packed Bed ◽  
Effect Of Temperature ◽  
Infrared Spectrometry ◽  
Packed Bed Column ◽  
Chromium Vi ◽  
Bed Height ◽  
Vis Spectroscopy

The present work aimed to evaluate the effect of temperature, particle size and bed height of the chromium (VI) adsorption process using plantain peels in a continuous system. The experiment was carried out on a packed bed column, adjusting the feed temperature of the solution with a REX-C100 controller coupled to a type K thermocouple. The initial concentration of Cr (VI) was set at 100 ppm, the pH at 2 and the feed rate of 0.75 mL/s. The analyses were performed by UV-Vis spectroscopy using the colourimetric method of 1.5-diphenylcarbazide. The material was characterized by infrared spectrometry by Fourier Transforms (FTIR), from this analysis, it was determined that the OH and NH2 functional groups are the main responsible for the formation of complexes with the cations in solution. Also, it was established that only the particle size is statistically significant. According to the response surface analysis, the optimum conditions of the process were 353.15 K, a particle size of 0.819 mm and a bed height of 67.768 mm. From the thermodynamic study of the process, it is established that it is endothermic and the chemical adsorption prevails in it. The results obtained in the process modelling suggest that Dose-Response can be used reliably to scale the process.

Structure determination of the 1/1 α/β mixed lactose by X-ray powder diffraction

2005 ◽  
Vol 61 (4) ◽  
pp. 455-463 ◽  
Author(s):  
Jacques Lefebvre ◽  
Jean-François Willart ◽  
Vincent Caron ◽  
Ronan Lefort ◽  
Frédéric Affouard ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Size Effects ◽  
Room Temperature ◽  
Real Space ◽  
Hydroxyl Groups ◽  
Soft Constraints ◽  
Rietveld Refinements ◽  
X Ray ◽  
Mixed Compound

The mixed form of α/β lactose was obtained by heating amorphous α-lactose at 443 K. NMR spectroscopy determined the stoichiometry of this mixed compound to be 1/1. The X-ray powder diffraction pattern was recorded at room temperature with a sensitive curved detector (CPS 120). The structure was solved by real-space methods (simulated annealing) followed by Rietveld refinements with soft constraints on bond lengths and bond angles. The H atoms of the hydroxyl groups were localized by minimization of the crystalline energy. The cell of 1/1 α/β lactose is triclinic with the space group P1 and contains two molecules (one molecule of each anomer). The crystalline cohesion is achieved by networks of O—H...O hydrogen bonds. The width of the Bragg peaks is interpreted through a microstructural approach in terms of isotropic strain effects and anisotropic size effects.

Toxic and mutagenic effects of chromium(VI). A review

Polyhedron ◽  
1996 ◽  
Vol 15 (21) ◽  
pp. 3667-3689 ◽  
Author(s):  
Maria Cieślak-Golonka
Keyword(s):  
Chromium Vi ◽  
Mutagenic Effects

Enhanced Thermal Stability of Esterified Lignin in Different Solvent Mediums

2018 ◽  
Vol 9 (1) ◽  
pp. 39-49 ◽  
Author(s):  
Sharifah Nurul Ain Syed Hashim ◽  
Sarani Zakaria ◽  
Chin Hua Chia ◽  
Sharifah Nabihah Syed Jaafar
Keyword(s):  
Thermal Stability ◽  
Alkaline Solution ◽  
Room Temperature ◽  
Hydroxyl Groups ◽  
Aqueous Alkaline Solution ◽  
Alkali Lignin ◽  
Weight Percentage ◽  
H Nmr ◽  
Ft Ir ◽  
Thermal Stability Of

In this study, soda alkali lignin from oil palm empty fruit bunch (EFB-AL) and kenaf core (KC-AL) are esterified with maleic anhydride under two different conditions, namely i) pyridine at temperature of 120°C for 3h and ii) aqueous alkaline solution at room temperature for 4h. As a result, the weight percentage gain (WPG) of the esterified EFB-AL (EFB-EL) and esterified KC-AL (KC-EL) in pyridine demonstrated a higher compared to aqueous alkaline solution. The FT-IR results of EFB-EL and KC-EL in both solvents exhibited some changes at the carbonyl and hydroxyl groups. Furthermore, the esterification process induced the carboxylic peak to appear in both alkali lignin samples. The outcome is confirmed by conducting H-NMR analysis, which demonstrated ester and carboxylic acid peaks within the spectral analysis. Finally, the TGA results showed both EFB-EL and KC-EL that are exposed to aqueous alkaline actually possessed better thermal stability and higher activation energy (Ea) compared to the esterified samples in pyridine.

Structure determination of the stable anhydrous phase of α-lactose from X-ray powder diffraction

2005 ◽  
Vol 61 (2) ◽  
pp. 185-191 ◽  
Author(s):  
Cyril Platteau ◽  
Jacques Lefebvre ◽  
Frederic Affouard ◽  
Jean-François Willart ◽  
Patrick Derollez ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Room Temperature ◽  
Structural Model ◽  
Hydroxyl Groups ◽  
Rietveld Refinements ◽  
X Ray ◽  
Hydrogen Bond Networks ◽  
Monte Carlo Simulated Annealing ◽  
Annealing Method

The stable anhydrous form of α-lactose has been obtained by the dehydration of α-lactose monohydrate in methanol. An X-ray powder diffraction pattern was recorded at room temperature with a laboratory diffractometer equipped with an INEL curved sensitive detector CPS120. The starting structural model of this form was found by a Monte-Carlo simulated annealing method. The structure was obtained through Rietveld refinements and the minimization of crystalline energy for the localization of the H atoms of the hydroxyl groups. Soft restraints were applied to bond lengths and angles. Networks of O—H...O hydrogen bonds account for the crystalline cohesion. A comparison is made between the hydrogen-bond networks of this form and those of the monohydrate and hygroscopic anhydrous forms of α-lactose.

scholarly journals The Novel Use of Saraca thaipingensis Leaf Powder as Potential Biosorbent Material for the Removal of Chromium(VI)

2015 ◽  
Vol 3 (3) ◽  
pp. 35-39
Author(s):  
Sannasi Palsan ◽  
Chai Swee Fern ◽  
Stephanie Bernardine ◽  
Lim Fan Shiang
Keyword(s):  
Heavy Metals ◽  
Particle Size ◽  
Contact Time ◽  
Low Cost ◽  
Peninsular Malaysia ◽  
The Novel ◽  
Batch Experiments ◽  
Chromium Vi ◽  
Removal Of Heavy Metals ◽  
Leaf Powder

Saraca thaipingensis or ‘Gapis’ tree, classified under the Fabaceae family is a native of Taiping; copious over Peninsular Malaysia and Southeast Asia. The withered and fallen dead leaves were collected from INTI International University’s garden walkway. To date, literature has yet to capture the use of S. thaipingensis tree parts or refuse as potential biosorbent material for the removal of heavy metals thus verifying the novelty of this study. Batch experiments were carried out with the leaf powder to study the effects of dosage, particle size and contact time towards Cr(VI) removal (%) at 1-100 mg/L. Results showed that Cr(VI) removal increased from 52.22% to 99.31% (p < 0.05) with increase in biosorbent dosage (0.005, 0.010, 0.015, 0.020, 0.025 and 0.050 g). The different particle size ranges tested were: 107-125, 126-150, 151-250, 251-500, and 501- 1000 ?m. Highest Cr(VI) removal of 99.53% was obtained with the 151-250 ?m particle size; further size decrease did not yield more removal (p > 0.05). The optimal Cr(VI) removal was recorded after 45 min (99.62%) and 90 min (99.76%) contact time (p > 0.05). Further characterization and optimization studies are being carried out to develop a novel, sustainable, low cost yet effective leaf powder based biosorbent material.

scholarly journals The Isomorphous Structures of Ammonium trans-Diiodobis(ethanedial-dioximato-(1–)-N,N′)cobaltate(III) and Ammonium trans-Diiodobis(ethanedial-dioximato-(1–)-N,N′)rhodate(III): Extended Metaloximate Chains with a Novel ···I–M–I···I–M–I··· Zigzagged Structure

1990 ◽  
Vol 45 (11) ◽  
pp. 1508-1512 ◽  
Author(s):  
Michel Mégnamisi-Bélombé ◽  
Bernhard Nuber
Keyword(s):  
Room Temperature ◽  
Ammonium Salts ◽  
Monoclinic Space Group ◽  
Hydroxyl Groups ◽  
Coordination Geometry ◽  
Crystal Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Anionic Complexes ◽  
Complex Anions

The ammonium salts of the complex anions trans-diiodobis(ethanedial-dioximato)-cobaltate(III), [Col2(GH)2]-, and trans-diiodobis(ethanedial-dioximato)rhodate(III), [RhI2(GH)2]- (GH- = ethanedial dioximate or glyoximate), have been synthesized and their structures determined from single crystal X-ray diffraction data at room temperature. The crystals of the two salts are monoclinic, space group C2/c. NH4[CoI2(GH)2] (I) crystallizes as dark-brown prisms with a greenish reflectance; its crystal data are: C4H10Col2N5O4, Mr = 504.90; a = 8.910(6), b = 11.700(9), c = 11.691(6) Å; β = 93.55(5)°; V = 1216.4 Å3; Z = 4; Dc = 2.78 Mg m-3. NH4[RhI2(GH)2] (II) crystallizes as yellow-brown blocks with crystal data: C4H10I2N5O4Rh, Mr = 548.88; a = 9.038(4), b = 11.949(5), c = 11.770(3) Å; β = 95.54(3)°; V = 1265.16 A3; Z = 4; Dc = 2.87 Mg m-3. The two structures were refined to a final RW = 0.045 for 1209 observed independent reflections and 95 parameters for I, and to a final RW = 0.040 for 1922 observed independent reflections and 87 parameters for II. The coordination geometry around Co or Rh in the anionic complexes is a distorted (4 + 2) octahedron of four equatorial chelating N atoms and two apical iodides. The H atoms of the hydroxyl groups are involved, as usual, in intramolecular O—H—O bridges with uniform Ο···Ο separations of 2.582 Å for I, and 2.713 Å for II. The rectilinear I—Co—I or I—Rh—I triads form “infinite” zigzag chains extending parallel to the ab plane, with a weak I—I contact of 3.988 Å for I, and 4.010 Å for II.

Methylation of Phenolic Hydroxyl Group and Demethylation of Anisoles

2009 ◽  
Vol 2009 (4) ◽  
pp. 229-230 ◽  
Author(s):  
Nobuhiro Sato ◽  
Hiroyuki Endo
Keyword(s):  
Microwave Heating ◽  
Room Temperature ◽  
Reverse Reaction ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Group ◽  
Hydroxyl Groups ◽  
Phenolic Hydroxyl Groups ◽  
Phenyl Ethers ◽  
Methyl Phenyl

A mild methylation of phenolic hydroxyl groups with iodomethane was enabled in the presence of sodium bis(trimethylsilyl)amide at room temperature. The reverse reaction, namely demethylation of methyl phenyl ethers, was easily achieved by microwave heating with neat iodotrimethylsilane.

Hollow structured CoSn(OH)6-supported Pt for effective room-temperature oxidation of gaseous formaldehyde

2016 ◽  
Vol 09 (06) ◽  
pp. 1642009 ◽  
Author(s):  
Jing Zhou ◽  
Yong Zhao ◽  
Lifan Qin ◽  
Chen Zeng ◽  
Wei Xiao
Keyword(s):  
Electron Microscopy ◽  
Catalytic Activity ◽  
Room Temperature ◽  
Synergetic Effect ◽  
Hollow Structure ◽  
Pt Nanoparticles ◽  
Hydroxyl Groups ◽  
High Catalytic Activity ◽  
Temperature Oxidation ◽  
X Ray

Uniform CoSn(OH)6 hollow nanoboxes and the derivative with Pt loading (Pt/CoSn(OH)6) were herein synthesized and characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). SEM and TEM analyses showed that CoSn(OH)6 possessed mesoporous hollow structure and Pt nanoparticles with size of 2–8[Formula: see text]nm were uniformly dispersed on the surface of CoSn(OH)6 nanoboxes. The performances of the catalysts for the formaldehyde (HCHO) removal at room temperature were evaluated. These Pt/CoSn(OH)6 catalysts exhibited a remarkable catalytic activity as well as stability for room-temperature oxidative decomposition of gaseous HCHO, while the corresponding CoSn(OH)6 only showed adsorption. The synergetic effect between the highly dispersed Pt nanoparticles and the CoSn(OH)6 nanoboxes with mesoporous hollow structure, a large surface area and abundant surface hydroxyl groups is considered to be the main reason for the observed high catalytic activity of Pt/CoSn(OH)6.

Effect of Process Parameters on the Adsorption of Chromium VI on a Packed Bed Column (PBC) using Vetiver (Vetiveria zizanioides)

2021 ◽  
Vol 25 (12) ◽  
pp. 53-59
Author(s):  
Pejavara Narayana Gururaj ◽  
Kulathooran Ramalakshmi ◽  
Sureshkumar Sujithra ◽  
Ravichandran Shalini
Keyword(s):  
Process Parameters ◽  
Oxygen Demand ◽  
Packed Bed ◽  
Heating Process ◽  
Tannery Effluent ◽  
Vetiveria Zizanioides ◽  
Experimental Conditions ◽  
Heated Sample ◽  
Packed Bed Column ◽  
Chromium Vi

The objective of this study is to evaluate the different process parameters on adsorption of chromium VI on a packed bed column using Vetiver (Vetiveria zizanioides) and to examine the effect of pH, Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD) at a constant contact time of 10 minutes at a temperature of 40 ºC under two experimental conditions namely, tannery effluent with and without microwave treatment. The results revealed that microwave heating process had a higher impact on chromium (VI) adsorption than normal heating process. The pH values of microwave treated sample were found to be 6.65±0.65 when compared to normal heated sample where the pH was 4.62±0.72 when compared to the initial pH of effluent found to be 3.47±0.58. Further, a threefold reduction in BOD and COD values was observed in microwave treated vetiver sample which was around 86.73±1.43 and 107.90±2.82 mg/l respectively when compared to normal heated sample (250±1.45 and 200±2.65 mg/l respectively) and untreated effluent (780±2.53 and 920±3.86 mg/l respectively) which indicated the reduction of chromium VI present in the effluent water. It was also observed that the metal adsorption capacity of the vetiver powder and the adsorption characteristics were positively correlated with the FTIR and SEM analysis which confirmed the presence of chromium (VI) on the surface of vetiver.

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