Saw-sedge <Emphasis Type="Italic">Cladium mariscus</Emphasis> as a functional low-cost adsorbent for effective removal of 2,4-dichlorophenoxyacetic acid from aqueous systems

For the first time in the published literature, a study is described concerning the use of the saw-sedge Cladium mariscus (C. mariscus) for adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) from aqueous systems. Among the experiments carried out, the elemental composition of C. mariscus was determined (C = 48.0 %, H = 7.1 %, N = 0.95 %, S = 0.4 %), FTIR spectroscopic analysis was performed to confirm the chemical structure of the adsorbent, and porous structure parameters were measured: BET surface area (A _BET  = 0.6 m²/g), total pore volume (V _p  = 0.001 cm³/g) and average pore size (S _p  = 6.6 nm). It was shown that the effectiveness of removal of 2,4-D from aqueous systems using C. mariscus depends on parameters of the process: contact time, system pH, mass of sorbent, and temperature. Maximum adsorption was attained for a solution at pH = 3. Further increase in the alkalinity of the tested systems led to a reduction in the effectiveness of the process. The kinetic of adsorption of 2,4-D by C. mariscus was also determined, and thermodynamic aspects were investigated. The experimental data obtained correspond to a pseudo-second-order kinetic model of type 1. Additionally the negative values obtained for ΔHº indicate that the process is exothermic, and the negative values of ΔGº show it to be spontaneous. As the temperature of the system increases the spontaneity of adsorption is reduced, in accordance with the exothermic nature of the process.     

Synthesis of water soluble metalloporphyrin-cored amphiphilic star block copolymer photocatalysts for an environmental application

Two series of water-soluble metalloporphyrin-cored amphiphilic star block copolymers were synthesized by controlled radical polymerizations such as atom transfer radical polymerization (ATRP) and reversible addition fragmentation chain transfer (RAFT), which gave eight amphiphilic block copolymer arm chains consisting of poly(n-butyl acrylate-b-poly(ethylene glycol) methyl ether methacylate) (PnBA-b-PEGMEMA, M_n,GPC = 78,000, M_w/M_n = 1.2, 70 wt% of PPEGMEMA) and poly(styrene-b-2-dimethylamino ethyl acrylate) (PS-b-PDMAEA, M_n,GPC = 83,000, M_w/M_n = 1.2, 67 wt% of PDMAEA), yielding porphyrin(Pd)-(PnBA-b-PPEGMEMA)₈ and porphyrin(Pd)-(PS-b-PDMAEA)₈, respectively. Obtained metalloporphyrin polymer photocatalysts were homogeneously solubilized in water to apply to the removal of chlorophenols in water, and was distinguished from conventional water-insoluble small molecular metalloporphyrin photocatalysts. Notably, we found that the water-soluble star block copolymers with hydrophobic–hydrophilic core–shell structures more effectively decomposed the chlorophenol, 2,4,6-trichlorophenol (2,4,6-TCP), in water under visible light irradiation (k = 1.39 h^?1, t_1/2 = 0.5 h) in comparison to the corresponding water-soluble star homopolymer, because the hydrophobic core near the metalloporphyrin effectively captured and decomposed the hydrophobic chlorophenols in water.     

Use of the ionic liquid trioctylmethyl ammonium dodecanedioate as a corrosion inhibitor of steel in production water

The properties of trioctylmethyl ammonium dodecanedioate (TAD) as a corrosion inhibitor (CI) of API 5L X52 steel in production water (PW) were evaluated in steady state using weight loss and polarization techniques within a Reynolds number (N _Re ) interval ranging from 500 to 40,000. The highest obtained IE was 87 % at 100 ppm with N _Re  = 2500, whereas the lowest IE was 15 % at 10 ppm with N _Re  = 4000. TAD was classified as a mixed-type CI of API 5L X52 steel in PW. The \(\Delta G_{\text{ads}}^{^\circ }\) data established a relationship between the N _Re and the adsorption process, confirming the occurrence of physical adsorption phenomena.     

A Search for a Direct Relationship Between Chromatographic and Adsorption Data

Shifts of chromatographic peak maxima and centres of gravity have been investigated for different amounts of propane injected on to a chromatographic column in ideal, non-linear chromatography. Specific retention volumes (V _{g (273)}, corrected to the standard temperature, 273.15 K), propane adsorption isotherms, and the first and second derivatives of the isotherms, (da/dp) _T and (d²a/dp²) _T , were determined for samples of active carbon and for different amounts of propane injected on column. Relationships between specific retention volume and the molar differential work of adsorption, A, were calculated on the basis of the propane isotherms and using the retention times of the peak maxima and the centres of gravity of the peaks. The equations obtained, ln V _{g (273)}=f₁(A) and(dW/dA) _{T, F c} = f₂(ln V _{g (273)}), have been used to explain the relationships between (i) chromatographic peak profiles and (ii) the distribution function of pore volumes filled with propane and the molar differential work of adsorption at different column temperatures (303–318 K).     

Adsorptive recovery of geniposidic acid from gardenia yellow pigment extraction wastewater by anion exchange: equilibrium,thermodynamics and mechanism modeling and simulation

For many years, the traditional process of gardenia yellow pigment extraction has produced wastewater containing significant quantities of Geniposidic acid (GSA), a substance that could be put to pharmacological uses if it could be effectively recovered. This study aimed to provide an efficient adsorption material, D08, for recycling GSA. Batch experiments showed that adsorption capacity depends on initial concentration and temperature. The maximal adsorption capacity of GSA onto an anionic exchanger reached 310 mg/g. The pK _a value of GSA was determined to be 4.21. Pore diffusion coefficients (D _p) of GSA for 283, 298 and 313 K were 3.274 × 10^?10, 5.069 × 10^?10 and 7.356 × 10^?10 m²/s, respectively. Recovery efficiency of GSA was achieved to 99.81 %. In comparison with pseudo first-order and pseudo second-order equations, the PDM model demonstrated the best fit to the kinetics data of GSA adsorption. Adsorption/desorption experiments proved that D08 offers great adsorption capacity, high adsorption rate and good repeatability. In order to help us to accurately comprehend the mass transfer process, numerical simulation and post-processing to variables c(r, t) and q(r, t) were performed to clarify the adsorption process.     

Synthesis,structural phase transition,and characterization of potassium hydrogen bis-dichloroacetate

Potassium hydrogen bis-dichloroacetate (1) was synthesized and separated as crystals. Differential scanning calorimetry (DSC) measurement reveals that this compound undergoes a reversible phase transition at about 259 K with a heat hysteresis of 23.5 K. Dielectric anomaly observed at 260 K in the heating process further confirms the phase transition. The room temperature X-ray single-crystal structure determination indicates that 1 crystallizes in the monoclinic crystal system with a centrosymmetric space group P2₁/c, and cell parameters are a =?6.240(1), b =?23.177(4), c =?7.335(1) Å, β =?106.938(1)°, V =?1014.8(3) ų, and Z =?4. In the low temperature phase, 1 also crystallizes in monolinic with space group P2₁/c, and cell parameters are a =?6.180(1), b =?22.988(2), c =?7.200(1) Å, β =?108.098(1)°, V =?972.4(1) ų, and Z =?4. The structural phase transition is dominating caused by the torsion of bond angles.     

New linear driving force correlation spanning long and short cycle time pressure swing adsorption processes

A simple, semi-empirical, generalized expression was developed for the LDF mass transfer coefficient k as a function of the half cycle time θ _c that encompasses and transitions between the well-known regions governed by the long cycle time constant Glueckauf k and the short cycle time dependent k. This new expression can be used to estimate k = f(θ _c ) for any system, irrespective of the loading and irrespective of θ _c , no matter if k is in the cycle time dependent region or not. A three times wider transition region between the Glueckauf k and the cycle time dependent k was also established, with the Glueckauf LDF limit now valid for θ _c  > 0.3 and the short cycle time limit now valid for θ _c  < 0.01. When evaluating this region for several adsorbate-adsorbent systems, the minimum Glueckauf θ _c spanned three orders of magnitude from thousands of seconds to just a few seconds, indicating a cycle time dependent k is not necessarily limited to what is normally considered a short cycle time. For virtually any θ _c less than this minimum Glueckauf θ _c , this new first-of-its-kind expression can be used to readily provide an accurate value of k = f(θ _c ). Since the widely accepted half cycle time concept does not apply to the actual simulation of a multi-step, unequal step time, pressure swing adsorption process, the value of k = f(θ _c ) from this new expression can be based on either the shortest cycle step in the cycle or a different value of k = f(θ _c ) for each cycle step time in the cycle, with validity confirmed either by experiment or by process simulation using the exact solution to the pore diffusion equation.     

Model-free temperature scaling for heat capacity

In treating the experimental data on the heat capacity of solids, the essence of any model application is in the searching for the scaling factors (k _i or 1/Θ_i) which transform a set of independent functions C _P,i(T) for every substance into a function C _P(T·k _i) universal for the particular set of substances. DSC heat capacities of I–III–VI₂ compounds at elevated temperatures exceed the upper limit of 12R (3R per mole of atoms) and make impossible application of any model. Nevertheless, the temperature scaling of heat capacity can be solved as a pure mathematical problem without any physical model (theory). The benefits of the model-free scaling are illustrated with the case of four isostructural chalcogenides (LiInS₂, LiInSe₂, LiGaS₂, and LiGaSe₂) measured recently with DSC in a temperature range from 180 to 460 K. The upper limit of C _P(T·k _i) functions was expanded up to 635 K. Low-temperature heat capacity of LiInSe₂ published in 1995 made it possible to derive the thermodynamic functions (enthalpy and entropy) for LiInS₂ (0–590 K), LiGaS₂ (0–640 K), and LiGaSe₂ (0–490 K) and expand those data for LiInSe₂ from 300 to 460 K.     

Effect of solvents on the morphology of NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript>/graphene nanostructures for electrochemical pseudocapacitor application

The large internal surface areas and outstanding electrical and mechanical properties of graphene have prompted to blend graphene with NiCo₂O₄ to fabricate nanostructured NiCo₂O₄/graphene composites for supercapacitor applications. The use of graphene as blending with NiCo₂O₄ enhances the specific capacitance and rate capability and improves the cyclic performance when compared to the pristine NiCo₂O₄ material. Here, we synthesized two different nanostructured morphologies of NiCo₂O₄ on graphene sheets by solvothermal method. It has been suggested that the morphologies of oxides are greatly influenced by dielectric constant, thermal conductivity, and viscosity of solvents employed during the synthesis. In order to test this concept, we have synthesized nanostructured NiCo₂O₄ on graphene sheets by facile solvothermal method using N-methyl pyrrolidone and N,N-dimethylformamide solvents with water. We find that mixture of N-methyl pyrrolidone and water solvent favored the formation of nanonet-like NiCo₂O₄/graphene (NiCoO-net) whereas mixture of N,N-dimethylformamide and water solvent produced microsphere-like NiCo₂O₄/graphene (NiCoO-sphere). Electrochemical pseudocapacitance behavior of the two NiCo₂O₄/graphene electrode materials was studied by cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy techniques. The supercapacitance measurements on NiCoO-net and NiCoO-sphere electrodes showed specific capacitance values of 1060 and 855 F g^?1, respectively, at the current density of 1.5 A g^?1. The capacitance retention of NiCoO-net electrode is 93 % while that of NiCoO-sphere electrode is 77 % after long-term 5000 charge-discharge cycles at high current density of 10 A g^?1.     

Dye removal using 4A-zeolite/polyvinyl alcohol mixed matrix membrane adsorbents: preparation,characterization, adsorption,kinetics, and thermodynamics

In pursuit of improving performance of the methylene blue adsorption process, the potential of a novel 4A-zeolite/polyvinyl alcohol (PVA) membrane adsorbent was investigated. Adding 4A-zeolite particles to the PVA membrane adsorbent provided an effective structure for the adsorptive membrane in dye removal processes. Effect of zeolite content was also studied via synthesis of different mixed matrix membrane adsorbents (MMMAs) with 5, 10, 15, and 20 wt% 4A-zeolite content. Morphology of MMMAs was analyzed by scanning electron microscope and the intermolecular interactions were determined by Fourier transform infrared spectroscopy. X-ray diffraction was performed to determine the crystal structure of MMMAs. For the sake of finding optimum condition, the adsorption capacity was examined at various operating parameters, such as contact time, temperature, pH, and initial concentration. The maximum value of the adsorption capacity (q _e) of 41.08 mg g^?1 and the highest removal efficiency of 87.41 % were obtained by applying 20 wt% loading of 4A-zeolite. The experimental data were fitted well with the Freundlich adsorption isotherm model (R ² = 0.9917) compared with the Langmuir (R ² = 0.9489) and the Tempkin (R ² = 0.8886) adsorption isotherm models, and the adsorption kinetic data verified the best fitting with the pseudo-second-order model (R ² = 0.9999). The estimated data for Gibb’s free energy (ΔG°) showed that the adsorption process is spontaneous at lower temperature values and non-spontaneous at higher temperature values. Other evaluated thermodynamic parameters such as changing in enthalpy (ΔH°) and entropy (ΔS°) revealed that the adsorption process is exothermic with an increase in orderliness at the solid/solution interface.     

Oxygen isotope exchange in praseodymium nickelate

Oxygen surface exchange kinetics and diffusion were studied in Pr₂NiO_4?+?δ (PNO) by the isotope exchange method with gas phase equilibration in the temperature range of 600–800 °C and oxygen pressure range of 0.33–1.62 kPa. The oxygen heterogeneous exchange rate (r_H), oxygen diffusion coefficient (D), rates of oxygen dissociative adsorption (r_a), and oxygen incorporation (r_i) were calculated along with the apparent activation energies of oxygen surface exchange and diffusion processes. The temperature dependence of r_H was found to benon-linear in Arrhenius coordinates. The apparent activation energy changed from 1.4?±?0.2 eV at T?>?700 °C to 2.0?±?0.1 eV. This might be attributed to the change in the rate-determining stage of oxygen exchange for Pr₂NiO_4?+?δ at T ~?700 °C, because of a shift in the ratio between r_a and r_i caused by the difference in their activation energies. Possible reasons for the observed changes in the rate-determining stage are discussed.     

Experimental investigation of radiocesium sorption on ceramic clay using a batch method

In this study, radiocesium sorption on ceramic clay was investigated as a function of particle size and initial ¹³⁷Cs concentration using a batch method. Ceramic clay samples taken from the Sö?üt(?nisar) clay deposit were composed of kaolinite, dickite and quartz. The equilibrium time and the liquid–solid ratio were determined as 60 min and 250 mL g^?1, respectively. The distribution coefficients (K _d) for variable liquid–solid ratio and the percentage adsorption (P _Ad) were calculated. The values of K _d and P _Ad ranged from 483 to 3165 mL g^?1 and 34–93%, respectively. The K _d and P _Ad values increased with increasing particle size, but decreased with increasing initial concentration. The sorption data were interpreted in terms of a Langmuir isotherm. The results indicated that the Sö?üt(?nhisar) ceramic clay has good sorption capacity for cesium.     

Facile synthesis of 5A zeolite from attapulgite clay for adsorption of <Emphasis Type="Italic">n</Emphasis>-paraffins

5A zeolites were facilely synthesized from attapulgite clay and sodium aluminate precursors. The optimum synthesis condition for 4A zeolite (Na-form) were H₂O/attapulgite ratio of 40:1 volume/mass, NaOH/attapulgite mass ratio of 2.35:1, the crystallization time was 4 h at 80–85 °C. The 4A zeolite was converted to related 5A zeolite (Ca-form) through ionic exchanges using calcium chloride solution with the Si/Al mole ratio of 1.3. SEM images demonstrated that as-synthesized 5A zeolites are ordered cubic crystals, average crystals length dimension is 1–2 μm. And the zeolites product had a specific surface area of 482 m² g^?1 and total pore volume of 0.274 cm³ g^?1. The static adsorption experiments showed that the equilibrium adsorption capacities of n-decane and n-pentadecane on produced 5A zeolite were 0.253 and 0.510 g g^?1, respectively. And the adsorption equilibrium time of n-decane and n-pentadecane on 5A zeolite were 45 and 60 min, respectively. The experimental adsorption data of n-decane and n-pentadecane on three zeolites could be properly fitted by the Langmuir–Freundlich isotherm model.     

Crystallographic and conformational analysis of (<Emphasis Type="Italic">E</Emphasis>)-2-isopropyl-4-(<Emphasis Type="Italic">p</Emphasis>-tolyldiazenyl)phenol

The molecular and crystal structures of the title compound, C₁₆H₁₈N₂O, were characterized and determined by single crystal X-ray diffraction method in addition to spectroscopic means such as IR, UV–VIS and ¹H NMR. The compound crystallizes in orthorhombic space group P bca, with a = 9.3350(5) Å, b = 23.4878(13) Å, c = 26.5871(12) Å, Z = 16, D _calc. = 1.1591(1) g/cm³, μ (MoK_α) = 0.073 mm^?1. Monomers of the compound in the crystal structure are linked into C(7) and C(8) chains generated by translation along the [1 0 0] direction with the aid of O–H···N type H-bonds which serve to the stabilization of periodic organization of the molecules beside major and minor component in the disordered azo fragment. In order to describe conformational flexibility and the crystal packing effects on the molecular conformation, potential barriers regarding the rotation along both Ar–N bonds were calculated by varying the related torsional degrees of freedom in every 10° ranging from ?180° to +180° via quantum chemical calculations at DFT/B3LYP level.     

Apparent Molar Volumes of Aqueous Solutions of Magnesium Tetraborate from 283.15 to 363.15 K and 0.1 MPa

Densities for aqueous solutions of magnesium tetraborate MgB₄O₇(aq) at the molalities of (0.00556–0.03341) mol·kg^?1 were measured with an Anton Paar Digital vibrating-tube densimeter at temperature intervals of 5 K from 283.15 to 363.15 K and 0.1 MPa. Apparent molar volumes were obtained based on the experimental density data, and the 3D diagrams of the apparent molar volume (V _? ) of MgB₄O₇(aq) against temperature (T) and molality (m) were plotted. On the basis of the Vogel–Tamman–Fulcher equation, the coefficients of the correlation equation for densities of MgB₄O₇(aq) against temperature and molality were parameterized. According to the Pitzer ion-interaction model of the apparent molar volume, the temperature correlation equations of Pitzer single-salt parameters F(i,p,T)?=?a₀?+?a₁?×?T?+?a₂?×?T ²?+?a₃/T?+?a₄?×?ln(T)?+?a₅?×?T ³ (where T is temperature in Kelvin, a _i are model parameters) for MgB₄O₇ were obtained for the first time.     

Adsorption of thorium (IV) by amorphous silica; response surface modelling and optimization

The amorphous SiO₂ (200–300 nm) was synthesized as an absorbent and thorium adsorption of SiO₂ was investigated using experimental and RSM method. The SiO₂ particles were made for the adsorption of thorium from aqueous solutions, and characterized by particle size measurement, XRD and SEM. The adsorption of thorium process was optimized with RSM method. The correlation between four variables was modeled and studied. Under optimum conditions, the adsorption capacity of SiO₂ particles was found to be 134.4 mg/g, the correlation coefficient (R²) and the F value was obtained 0.96 and 1.98?×?10^?6, respectively. In addition, the adsorption isotherms were examined.     

Synthesis,crystal structure,and hydrogen-bonded displacive-type structural phase transition of guanidine dichloroacetate

Guanidine dichloroacetate was synthesized and separated as crystals. Differential scanning calorimetry (DSC) measurement shows that this compound undergoes a reversible phase transition at about 275 K with a heat hysteresis of 28 K. Step-like dielectric anomaly observed at 274 K further confirms the phase transition. The single-crystal X-ray diffraction data suggested that these was a transition from a room-temperature phase with the space group of P2₁/n (a = 8.030(5), b = 12.014(9), c = 8.124(6) Å, β = 96.089(1)°, V = 779.3(1) Å³, and Z = 4) to a low-temperature one with the space group of P2₁/c (a = 7.941(2), b = 11.828(3), c = 10.614(2) Å, β = 130.985(1)°, V = 752.6(3) Å³, and Z = 4). The displacements of hydrogen bonds induce the structure phase transition.     

Adsorptive recovery of an essential rose oil component from aqueous solution by nanoporous carbon (CMK-3)

A nanoporous carbon (CMK-3) was synthesized and used to adsorb 2-phenylethanol (PEA) from aqueous solutions. The characterization of CMK-3 by N₂ adsorption isotherm revealed the formation of a nanoporous carbon with average pore diameter and surface area of 3.34 nm and 1268 m² g^?1, respectively. Column-like particle morphology of CMK-3 was observed from scanning electron microscope images. To evaluate the feasibility of CMK-3 as a potential PEA adsorbent, batch adsorption experiments were conducted for aqueous PEA solutions. The results showed that CMK-3 is an efficient sorbent for the separation of PEA from water. The optimized adsorbent doses were found to be 0.3 and 2.2 g L^?1 for 30 and 300 mg L^?1 PEA, respectively. Our studies about the effect of pH on CMK-3 adsorption capacity revealed that the adsorption capacity increased at lower pH due to the protonation of PEA. Three adsorption models, Langmuir, Freundlich and Temkin were used to describe the adsorption isotherms. Thermodynamic parameters such as ΔG ⁰, ΔH ⁰, and ΔS were also evaluated, and it was found that the sorption process was spontaneous, endothermic, and physical in nature. The adsorption kinetics was investigated in detail and the pseudo-second-order kinetic equation fitted the experimental data very well. The mechanistic study by Weber-Morris model revealed that the overall adsorption process was simultaneously governed by external mass transfer and intraparticle diffusion. Almost all (97 %) adsorbed PEA was successfully recovered into ethanol which is a common solvent in fragrance industry. CMK-3 was proved to be a promising adsorbent for the adsorption-recovery of PEA from aqueous solution.     

Substituent effects on the kinetics of acid-catalyzed hydrolysis of methyl cellulose

The kinetics of the hydrolysis of methyl cellulose (MC, DS 1.27 and 1.95) was studied by a two-step procedure, comprising partial hydrolysis in 1 M TFA in water and water/acetone at 120 °C for various time periods, labeling of generated reducing ends by reductive amination, complete depolymerization by methanolysis followed by trimethylsilylation, and gas chromatographic analysis of the two sets of partially O-methylated glucose derivatives. Rate constants of MCs were all in the order of 10^?4 s^?1. In aqueous TFA, overall rate of hydrolysis of the MC with lower DS was faster than of the MC with higher DS. When substituting half of the water by acetone, reaction was slowed down while selectivity regarding different O-methyl glucosyl residues increased. Compared to the parent glucosyl unit methylation at O-2 and at O-6 decreased rate of hydrolysis, while 3-O-methyl favored it especially in the early stage of the conversion of the macromolecules. Beside slight differences between the two MCs and reaction conditions, rate constants k _i (i = position of methyl) followed the order k ₃₆ ≈ k ₃ > k ₀ ≈ k ₂₃ > k ₆ > k ₂ ≥ k ₂₃₆ > k ₂₆. For the higher substituted MC2 an initial slow phase with more pronounced differences of k _i, followed by a faster less selective period was observed. Regioselectivity of hydrolysis with respect to methyl positions was expressed as standard deviation of k _i and was between 16 and 46% depending on MC and conditions. Findings are discussed with respect to electronic effects, solvent-effect, H-bonding pattern and solution state.     

Effect of Ag addition on crystallization kinetics and thermal stability of As–Se chalcogenide glasses

Chalcogenide glasses of (As₅₀Se₅₀)_100?xAg_x (0 ≤ x ≤ 25) were prepared using the melt quenching technique under non-isothermal conditions. Differential scanning calorimetry curves measured at different heating rates (5 ≤ β ≤ 40 K min^?1) are used to characterize the as-quenched samples. The thermal stability was monitored through the calculation of the temperature difference T _c ? T _g, stability parameter S and crystallization rate factor K _p. The glass-forming ability (GFA) was investigated on the basis of Hurby parameter H _r which is a strong indicator of GFA. In addition, the activation energy of glass transition E _t, activation energy of crystallization E _c and Avrami exponent n of the studied compositions were determined. The mechanism of crystallization was found to be a combination of two- and three-dimensional crystal growth.