Poor Desorption Research Articles

Room Temperature Storage of Methane by Bamboo-Like Carbon Nanotubes

Single carbon nanotubes (CNTs) have the sorption states at around 200 K, and show the poor desorption characteristics at around 300 K. The bamboo-like CNTs, HP1050 and the ground HP1050 (HP-1050G), show the desorption peaks at around 100 K and 140 K, respectively. Furthermore, HP1050G has the sorption states at around 300 - 400 K. On the basis of the sorption process, the ground bamboo-like CNT has a possibility for application to the room temperature storage of methane, which has utility for energy technologies such as fuel cells.

Investigation and optimization of particle dimensions for needle trap device as an exhaustive active sampler

Various needle trap devices (NTDs) with different designs have been developed during the past decade. A theoretical model on the fundamentals of the NTD was recently proposed, which employed the theory of frontal (gas–solid) chromatography to describe the sampling process. In the current work, different types of sorbent particles with different dimensions were packed into the needle as the adsorbent. The effects of particle dimensions, which would affect the packing density and consequently affect the capacity, the extraction efficiency and desorption efficiency of the NTD were experimentally investigated and the proposed theory was validated. The results demonstrated that NTDs packed with small particles possess higher extraction capacity and efficiency but much higher resistances to flow as well. The higher resistance did not necessarily result in poor desorption efficiency. The observed relationships among those physical parameters provide valuable guidance on how to design a NTD with high performance for future applications.

Improved dehydrogenation performances of TiB2-doped sodium alanate

A systematic investigation is performed on the dehydrogenation performance of TiB2-doped NaAlH4. A dramatic enhancement in the dehydrogenation kinetics of NaAlH4 is achieved by adding as-prepared TiB2 catalyst based on a low temperature solid phase reaction, whereas pure NaAlH4 exhibits a poor desorption kinetics. Thermodynamic analyses show that the onset dehydrogenation temperature of as-prepared TiB2-doped NaAlH4 is lowered to about 75 °C. In addition, the experimental results show that as-prepared TiB2-doped NaAlH4 after milling releases 3.60 wt.% H2 for 1 h and 5.21 wt % H2 for 4 h at 190 °C with a excellent dehydriding rate and capacity.

Plant toxic and non-toxic nature of organic dyes through adsorption mechanism on cellulose surface

Effluents releasing from dyeing industries directly affect the soil, water, plant and human life. Among these dyes, plant poisoning, soil polluting and water polluting nature of organic dyes are not yet identified. The plant poisoning and non-poisoning organic dyes are identified through adsorption mechanism of cationic malachite green (MG) and anionic methyl orange (MO) on brinjal plant root powder (cellulose). The positive Δ H o (44 kJ mol −1) of MG higher than 40 kJ mol −1 confirmed the adsorption of MG on cellulose is chemisorption and the negative Δ H o (−11 kJ mol −1) less than 40 kJ mol −1 showed that the adsorption of MO on cellulose is physisorption. The Δ G o values for the adsorption of MG and MO on BPR are not much increased with increase of temperature which indicated that the adsorption is independent of the temperature. The entropy change for the adsorption of MG and MO has proved that the MG (+ΔS o) has less disorder at the adsorption interface and MO (−ΔS o) has the high disorder at the adsorption interface. The recovery of both dyes has been studied in water at 80 °C on BPR surface and observed that the MO recovery is 95% and MG is 10%. The poor desorption of MG is due to the strong chemisorption on BPR (cellulose) surface proves its plant poisoning nature. The high recovery of MO due to physisorption mechanism proves that MO is not poisoning the plant.

Recovery of cellulases by adsorption/desorption using cation exchange resins

Cellulases from Trichoderma reesei were recovered by adsorption in sodium acetate buffer at lower pH using cation exchange resins followed by desorption at higher pH. The weakly acidic ion exchange resin WK10 was found to be the best among the six resins tested in terms of the enzyme activity recovery. The optimal pH values for the adsorption and desorption were 4.0 and 8.0, respectively, and the optimal adsorption and desorption times were both 5 h. Almost 100% of the initial cellulase activity was recovered under the optimal conditions with the supplement of β-glucosidase, which was unable to be efficiently recovered due to its strong adsorption (95.7%) but poor desorption (1.9%).

Improvement in desorption kinetics of NaAlH 4 catalyzed with TiO 2 nanopowder

NaAlH 4 has been homogeneously mixed with micron- and nano-sized TiO 2 powders by high-energy ball milling and their sorption properties have been investigated during hydrogen absorption/desorption cycles. NaAlH 4 with TiO 2 nanopowder exhibits as good desorption kinetics as NaAlH 4 with TiCl 3, whereas poor desorption kinetics is observed with micron-sized TiO 2 powder. NaAlH 4 with TiO 2 nanopowder also provides improved cyclic property compared to NaAlH 4 with TiCl 3 in terms of both desorption rate and hydrogen capacity. X-ray diffraction analysis shows that micron-sized TiO 2 remains stable with NaAlH 4 after milling, although thermodynamic calculation predicts that TiO 2 reacts with NaAlH 4.

Adsorption of dissolved Reactive red dye from aqueous phase onto activated carbon prepared from agricultural waste

The adsorption of Reactive red dye (RR) onto Coconut tree flower carbon (CFC) and Jute fibre carbon (JFC) from aqueous solution was investigated. Adsorption studies were carried out at different initial dye concentrations, initial solution pH and adsorbent doses. The kinetic studies were also conducted; the adsorption of Reactive red onto CFC and JFC followed pseudosecond-order rate equation. The effective diffusion coefficient was evaluated to establish the film diffusion mechanism. Quantitative removal of Reactive red dye was achieved at strongly acidic conditions for both the carbons studied. The adsorption isotherm data were fitted well to Langmuir isotherm and the adsorption capacity were found to be 181.9 and 200 mg/g for CFC and JFC, respectively. The overall rate of dye adsorption appeared to be controlled by chemisorption, in this case in accordance with poor desorption studies.

Effect of surfactants on desorption of aldicarb from spiked soil

Surfactant enhanced desorption of aldicarb from spiked soil was investigated in this paper. Anionic (sodium dodecyl benzene sulphonate, SDBS), cationic (hexadecyl trimethyl ammonium bromide, HTAB) and nonionic (octyl polyethylene glycol phenyl ether, OP) surfactants were tested to determine their optimal desorption conditions including desorption time, mixing speed and surfactant concentrations. The results showed that the optimal operating conditions were obtained at 2 h, 150 rpm, and surfactants concentrations were 1000, 100, and 200 mg l −1 for SDBS, OP, and HTAB, respectively. The paper also investigated the desorption efficiency of mixture of different kinds of surfactants for aldicarb-spiked soil, and found that anionic–nonionic surfactant mixtures gave the best desorption efficiency up to 77%, while anionic–cationic surfactant mixture gave a poor desorption efficiency similar to water, suggesting that mixture of anionic–nonionic surfactants were highly promising on remediation of aldicarb-contaminated soil.

Chemical contamination and toxicity of sediment from a coastal area receiving industrial effluents in Kuwait.

The Shuaiba coastal area (12.5 x 1.5 km) was examined for contamination with total organic carbon, volatile organic matter, total petroleum hydrocarbons, polycyclic aromatic hydrocarbons, cadmium, chromium, copper, lead, nickel, vanadium, and zinc in sediment; their desorption by aqueous elution; and toxicity to aquatic biota. The pollutants were mainly accumulated in the upstream area facing Mina Al-Ahmadi refinery to Shuaiba harbour. Solid-phase Microtox assays showed severe toxicity, and the LC(50) was negatively correlated with most of the chemical parameters, suggesting that toxicity was the function of collective effects of the pollutants present in sediment. Sea water elutriation showed poor desorption of pollutants from sediment, and the elutriates were not found toxic to Microtox and brine shrimp larvae. Whole sediment suspension in sea water reduced the survival of fingerlings in fish bioassays. Action from Shuaiba Area Authority is required to reduce pollutant accumulation in identified depositional area on the Shuaiba coast by facilitating unrestricted water flow in the area and restricting pollutant discharge at source.

Performance assessment of a passive sampler in industrial atmospheres.

In this work we investigate the performances of a passive sampler (GABIE badge) in industrial atmospheres, in accordance with the general specifications of the EN 838 standard. The field experiment was carried out in a paint-manufacturing factory producing a large number of pollutants at the workplaces. A comparison was performed between the results obtained by passive sampling and the conventional tube/pump method (reference method) on nine solvents usually encountered in the different workshops: n-butanol, isobutanol, toluene, ethylbenzene, m-xylene, methylisobutylketone, methylethylketone (MEK), ethyl acetate, butyl acetate. Results were compared by use of the distribution of the relative difference between badge "passive sampling" and tube "active sampling" results (with the latter considered as the reference method). In general, results revealed good agreement between passive and active sampling (except in the case of MEK) and confirmed the accuracy of sampling rates determined for the GABIE sampler. Bias was generally low and variability could be considered to be satisfactory (generally < 20% with a maximum of 30% for ethylbenzene). For MEK, strong bias was noted together with probable underestimation of the tube results. Additional results lead us to suggest that this phenomenon could be due to poor desorption of the SKC tubes by carbon disulphide (CS2); (quantitative recovery for MEK is in fact possible using other desorption solvents).

A Comparison of Two Diffusive Samplers for the Collection of Styrene, α-Methylstyrene, ando-Chlorostyrene Vapors

Abstract Styrene is a frequently encountered hazardous chemical in industry. Traditional methods of workplace air sampling involve the collection of vapors on a solid sorbent sampling tube, followed by laboratory desorption and analysis. The most common sorbent used is activated coconut shell charcoal, which exhibits poor desorption efficiencies at low styrene loadings. An alternative treated charcoal sorbent requires a more complex analytical procedure. In this study a diffusive sampler was validated for styrene according to a modified version of a protocol developed by the National Institute for Occupational Safety and Health. Two versions of the sampler were validated simultaneously, each having a different sorbent substrate. Both samplers passed the requirements of the validation procedure, including tests for desorption efficiency, uptake rate and capacity, reverse diffusion, storage stability, temperature effects, and a factorial study of concentration, sampling time, humidity, interferences, wind velocity, and sampler orientation, and their interactions. In total, 198 575-002 and 175 575-003 samplers were used in the full validation protocol. Both samplers were also tested for critical sampling parameters (desorption efficiency, uptake rate, and storage stability) according to the guidelines of the bi-level theory of sampler validation for the homologues α-methylstyrene and o-chlorostyrene. Sixty-four samplers of each type were used in the tests on α-methylstyrene, and 72 samplers of each type were used in the tests on o-chlorostyrene. While both samplers were shown to perform well, differences resulting from the use of different sorbents can be used to select the most appropriate sampler for a specific application. The uptake rates of the samplers for styrene, α-methylstyrene, and o-chlorostyrene are 13.7, 12.6, and 9.8 ml/min, respectively.

Determination of Alachlor, Atrazine, and Metribuzin in Soil by Resin Extraction

AbstractAn accurate and precise procedure for simultaneous resin extraction of alachlor (2‐chloro‐2′,6′‐diethyl‐N‐methoxymethylacetanilide), atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine), and metribuzin [4‐amino‐6‐(1,1‐dimethylethyl)‐3(methylthio)‐1,2,4‐triazin‐5(4H)‐one] in soil extracts is described. The procedure consists of three steps: (i) equilibration of resin extractors (RE) with water extracts of soil, (ii) elution of pesticides from RE by using methanol, and (iii) determination and confirmation of pesticide by dual‐column gas chromatography with thermionic specific detection. Recovery of dissolved pesticides by anion‐exchange resin, cation‐exchange resin, and nonpolar resin was studied. Ion‐exchange resins generally adsorbed pesticides well, but showed poor desorption characteristics. The effect of solution pH and salt concentration on pesticide adsorption by a nonpolar resin was studied. Quantitative amounts of pesticide (&gt;95%) were adsorbed from solution by a nonpolar resin over a wide range of solution pH (2.5–10.0) and dissolved salt (0–100 mM NaCl). Pesticide adsorbed by RE ranged from 80 to 90%, and methanol desorbed 80 to 85% of adsorbed pesticides. Overall pesticide recoveries by the RE procedure were very reproducible with an average recovery of 67.7 ± 2.0%. Results obtained by the RE procedure agreed closely with those obtained by solid‐phase extraction (SPE) with octadecyl (C18) bonded porous silica. Extraction time required by the RE procedure is a function of temperature and decreases from 5 d at 22 °C to 2 d at 75 °C. The RE procedure has the same degree of precision as C18‐SPE and is inexpensive.

Desorption and absorption of gases by drops during impact

AbstractA study has been made of the desorption and absorption of gases by liquid drops during the period of their impact on various types of surfaces, following previous work on absorption during formation and during flight of drops. On impinging on a surface, drops form spray, and ‘residual liquid’ which is not detached from the surface and ultimately drains away. The amount of desorption in the spray does not vary greatly with either the height of fall of the drops or the type of surface. In the residual liquid, poor desorption is obtained with ‘dry’ surfaces, i.e. well‐drained surfaces with an average liquid depth of less than 0·1 mm., and relatively good desorption with ‘wet’ surfaces. Desorption in the residual liquid increases to a moderate extent with the velocity of drops before impact, but appears to be little affected by the nature or the contour of the surfaces tested. The process of absorption or desorption is interpreted in terms of the dynamics of the impinging drop. For desorption measurements, water drops containing carbon dioxide were used; as far as could be judged by a limited number of experiments, absorption of oxygen by drops of sodium dithionite or sulphite solution appeared to be affected by factors similar to those found in desorption.