Effect Of Equilibrium Time Research Articles

Rapid and real-time analysis of multi-component dissolved gas in seawater by Raman spectroscopy combined with continuous gas−liquid separator

Rapid and sensitive detection of dissolved gases in seawater is quite essential for the investigation of the global carbon cycle. Large quantities of in situ optical detection techniques showed restricted measurement efficiency, owing to the single gas sensor without the identification ability of multiple gases. In this work, a novel gas−liquid Raman detection method of monitoring the multi-component dissolved gases was proposed based on a continuous gas−liquid separator under a large difference of partial pressure. The limit of detection (LOD) of the gas Raman spectrometer could arrive at about 14 μl·L−1 for N2 gas. Moreover, based on the continuous gas−liquid separation process, the detection time of the dissolved gases could be largely decreased to about 200 s compared with that of the traditional detection method (30 min). Effect of equilibrium time on gas−liquid separation process indicated that the extracted efficiency and decay time of these dissolved gases was CO2 >O2 >N2. In addition, the analysis of the relationship between equilibrium time and flow speed indicated that the decay time decreased with the increase of the flow speed. The validation and application of the developed system presented its great potential for studying the components and spatiotemporal distribution of dissolved gases in seawater.

Decolorization of Rhodamine B Dye by Hydeogel Nanocomposite: Thermodynamic and Kinetic Studies

Rhodamine B is used extensively in textile dyes and agricultural pesticides as fish pests. Hydrogel is a type of sorption technique used as a sorbent. As of now, adsorption is viewed as a cost-effective method that may be used as an alternative to traditional contamination treatment methods. Several techniques were utilized to determine the surface characteristics before and after the adsorption method, like fourier transform infrared (FTIR) and field emission scanning electron microscopy (FESEM) techniques. The effect parameter of the adsorption method was studied, such as the effect of equilibrium time and weight. The data showed that the best removal percentage was (E%=96.546%) and adsorption capacity (188.0 mg/g) in the same order. Thermodynamic factor studies have shown that the reaction is spontaneous, exothermic, and convenient. The sorption isotherm of Rhodamine B onto sodium alginate-g-poly (acrylic acid)/GO composite hydrogel was analyzed utilizing two models First order and second order. The second order was the poorest in a fit of the liner curve and the better.

Study on Extraction Performance of Vanadium (V) from Aqueous Solution by Octyl-Imidazole Ionic Liquids Extractants

It is worth it to explore the extraction performance for vanadium by the imidazole ionic liquids. The extraction of vanadium (V) was studied using [Omim]Cl, [Omim]Br, and [Omim][BF4] as extractants. The effects of various diluents, equilibrium time, extraction temperature, and anion species were investigated. The structure-activity relationship of vanadium and ILs was discussed by calculating the lattice energy of ILs based on the Glasser theory and the volume of anions. The results show that n-pentanol is the optimum diluent. Under the extraction conditions of an equilibrium time of 60 s and extraction temperature of 25 °C, the extraction rates of V (V) by [Omim]Cl, [Omim]Br, and [Omim][BF4] reached 97.93%, 96.59%, and 87.01%, respectively. Furthermore, based on the Glasser theory, the lattice energy of ionic liquids decreased in the order [Omim]Cl > [Omim]Br > [Omim]BF4. The volume of the anions increased in the order Cl− < Br− < BF4− < HVO42−. The extraction rate of V (V) depended on the size of the anions and the strength of the interaction between the anion and imidazolium cation. The results of counterevidence experiments verified the larger the anion volume, the easier it is to combine with cation in the organic phase, and the lattice energy of extracted compound is lower. The statistical analysis showed that the effect of the equilibrium time and temperature were not significant in the model, and the anions species showed a significant effect on the extraction efficiency of V (V).

Effects of equilibrium time and adsorption models on the characterization of coal pore structures based on statistical analysis of adsorption equilibrium and disequilibrium data

Low-pressure CO2 adsorption is an important tool for quantitatively characterizing the micropore characteristics of porous materials. While only adsorption data obtained at adsorption equilibrium will ensure the accuracy of the method. In this paper, 82 sets of CO2 adsorption equilibrium and disequilibrium data of coal samples with different particle sizes were investigated, and the influence of equilibrium criterion and data analysis methods on the adsorption data and calculation of pore characteristics was studied by statistical analysis method. Furthermore, to explore methods to distinguish between low-pressure CO2 adsorption equilibrium and disequilibrium data, the correlation between different analysis methods and the adsorption equilibrium and disequilibrium data were then analyzed. The results suggest: for the coal samples with complex micropore structures, the linearly increasing CO2 adsorption isotherm is most likely caused by the disequilibrium adsorption; the analysis on adsorption disequilibrium data often leads to underestimation of the pore structures in small pore size range, and moreover the Dubinin–Astakhow method (D–A) is particularly sensitive to adsorption disequilibrium data, which would lead to great errors for the calculation of pore characteristics; the more developed the micropore structures, the higher the demarcation point between the correlation coefficient of the Dubinin–Radushkevich method (D–R) and adsorption equilibrium and disequilibrium data, where the fitting errors obtained by using the Monte–Carlo method (M–C) to fit the adsorption equilibrium data were mostly less than 0.2. This study could provide some guidance for more accurate use of gas physisorption methodology, especially for porous solid materials with complex micropore structures like coal.

Development of microporous activated Aloji clay for adsorption of lead (II) ions from aqueous solution

Aloji clay was activated with HCl at optimal conditions variables (acid concentration, activation temperature and time) using central composite design with yield (%) and Pb2+ uptake as responses targeted. The obtained optimum conditions for high yield (%) and Pb2+ uptake were at 0.5 M, 100 °C and 120 min. At these conditions, BET surface area of 214.80 m2/g of the microporous activated adsorbent gave a maximum monolayer of 333.33 mg/g for Pb2+. The effects of equilibrium time, initial Pb2+ concentration, temperature and adsorbent dosage were examined. Pseudo-second-order kinetic and Freundlich models best described Pb2+ adsorption onto Aloji activated clay as compared to the other isotherms and kinetics models investigated. The adsorption process was spontaneous, exothermic and physical as revealed by the nature of the thermodynamic studies. The study shows that the discharge of harmful substances posed by industrials into water bodies can be salvage by effective and efficient use of activated Aloji clay.

Microporous carbon from cashew nutshell pyrolytic biochar and its potential application as CO2 adsorbent

Cashew nutshell (CNS)–based biochar is obtained as a by-product in a pilot scale (20 kg/h) gas-fired auger pyrolysis reactor at 500 °C during bio oil production. This pyrolytic biochar has low BET surface area (BET SA 0.80 m2/g) and poor porosity as the fast pyrolysis conditions are set to augment the bio oil yield over other products. To value add to this carbon, downstream activation is performed in an externally heated lab scale reactor. Formation of activated carbon with BET SA between 300 and 700 m2/g with moderate improvement in porosity ensued from CO2 and steam activation, while chemical activation with K2CO3 enhanced the BET SA to 1225 m2/g and Langmuir surface area to 1707 m2/g in addition to significant enhancement of porosity. CNS-based activated carbons predominantly possess narrow pore size distribution with small-sized micropores and ultra-micropores limiting the presence of mesopores. The effect of equilibrium time (10 s and 45 s) on N2 adsorption is extensively studied, and it is found to have a significant role in detection of ultra-micropores below 0.8 nm (at very low pressures). The CO2 absorptivity of K2CO3-activated CNS carbon is found to be between 4.16 and 6.22 mmol/g (i.e. 183.04–273.6 mg/g) at atmospheric pressure and 0 °C. These activated CNS carbons possess ultra-micropores between 0.46 and 0.8 nm suitable for CO2 uptake. This study shows the sustainable path of making CO2 adsorbent from a low-cost renewable biomass precursor like CNS.

Removal of Reactive Orange 16 by adsorption onto activated carbon prepared from rice husk ash: statistical modelling and adsorption kinetics

ABSTRACT Low cost activated carbon was produced by treated rice husk ash for adsorptive removal of Reactive Orange 16. The selection of adsorbents, effect of equilibrium time, adsorbent dosage, concentration of dye, and pH on removal of dye was optimized as rice husk ash, 30 min, 0.25 g/100 mL, 100 mg/L, and 9.0, respectively. The process fits into Langmuir isotherm and Lagergren pseudo-second-order model with rate constant of 0.0216 g/mg min. The process was statistically optimized and evaluated by face-centered central composite design. The maximum dye was removed (Qe = 13.32 mg/g) at adsorbent dosage of 0.25 mg/100 mL, pH of 11.0, and concentration of dye: 250 mg/L.

Recovery of methyl orange and Congo red from aqueous solutions using tri-octyl amine (TOA) in benzene as carrier

The recovery of anionic azo dyes namely Congo red (CR), methyl orange (MO) from acidic aqueous solutions using tri-octyl amine (TOA) as an extractant has been investigated. The percentage of extraction of MO and CR increases with an increasing TOA concentration. The anionic dyes were extracted from aqueous solution at pH 2.0±0.1. The extracted dye has been back extracted into aqueous solutions using sodium hydroxide, sodium carbonate and sodium bicarbonate. The organic phase obtained after the stripping of dyes was washed with dilute sodium hydroxide solution to neutralize any sulphuric acid trapped or adhered to the solvent and then with distilled water. This solvent was reused in succeeding extraction of dyes. The influencing parameters were; the effect of diluents, effect of extractant concentration, effect of pH, effect of interference study, effect of equilibrium time, various stripping reagents and stripping phase ratio. The characterization studies such as UV and IR spectra of extracted and stripped MO and CR was also studied.

Extraction and stripping of Cr(VI) from aqueous solution by solvent extraction

The solvent extraction of Cr(VI) from an aqueous solution by hexadecyl trimethyl ammonium bromide (HTAB) in amyl alcohol was investigated at 27°C. The maximum extraction efficiency was obtained at pH 1.0 ± 0.1. Chromate is an anionic form; therefore, it requires a cationic carrier for the extraction purpose and HTAB acts as cationic carrier in this study. The efficiency of extraction decreased with increasing the chromium concentration. The extracted Cr(VI) in the organic phase can be back extracted into 0.2 mol/L sodium nitrate. The important experimental parameters examined were: the effect of HTAB concentration, the effect of pH, the effect of Cr(VI) concentration, the effect of equilibrium time, and the effect of temperature, aqueous to organic phase ratio, and various stripping agents. Real effluent was also studied under optimized condition [Cr(VI) concentration 10 mg/L at pH 1.0 ± 0.1, carrier concentration = 0.06 mol/L, stripping concentration = 0.2 mol/L, and equilibrium time = 5 min at 27°C] and satisfactory result has been found.

Biosorption of Cu<sup>2+</sup> by Anaerobic Granular Sludge

In order to investigate the biosorption of Cu2+ by anaerobic granular sludge, the effect of equilibrium time, pH, sludge dosage, biosorption kinetics, biosorption thermodynamics and biosorption isotherms had been studied. Results showed that pseudo second-order kinetic model was useful to describe the biosorption process of Cu2+. Both Langmuir and Freundlich isotherm equations could well describe the desorption process at 15-55 °C. Thermodynamic studies showed that the biosorption process was spontaneous and endothermic in nature. When the solution temperature maintained at 35 °C, pH of 6~7, a good biosorption process could be obtained.

Recovery of methylene blue from aqueous solution by liquid–liquid extraction

The aim of this study is the removal and recovery of methylene blue (MB) from wastewater. MB is one of the most commonly used substances for dyeing cotton, wood, and silk. Though MB is not strongly hazardous, it can cause some harmful effects where acute exposure to MB may cause increased heart rate, vomiting, shock, cyanosis, jaundice and quadriplegia and tissue necrosis in human. So, we selected the MB for solvent/liquid–liquid extraction study. MB is the cationic dye, so it requires an anionic carrier for extraction purpose. Salicylic acid acts as an anionic carrier in this study. Removal of MB using salicylic acid in benzene was studied. The efficiency of dye extraction increased with decreasing dye concentration. The extracted dye in the organic phase can be back-extracted into 1M oxalic acid solutions. The experimental parameters examined were salicylic acid concentration, effects of diluents, effect of pH, effect of initial dye concentration, effect of equilibrium time, aqueous to organic phase ratio, and various stripping agents. Real effluent was also studied under optimized condition and satisfactory result has been found.

Removal of methylene blue from colored effluents by adsorption onto ZnAPSO-34 nanoporous material

The effects of equilibrium time, solution pH, and sorption temperature of cationic methylene blue (MB) adsorption on nanoporous metallosilicoaluminophosphate ZnAPSO-34 were studied using a batch equilibration method. UV–Vis spectroscopy was used to obtain the adsorption isotherms at 20°C. The optimum period for adsorption was 300 min. In fact, MB removal increased from 82 to 95% when we double the amount of adsorbent from 0.05 to 0.1g l−1. The equilibrium adsorption data were analyzed using Langmuir, Freundlich, and Temkin isotherm models. Langmuir isotherm was found to be the best-fitting model and the process followed pseudo-second-order kinetics. The results showed that ZnAPSO-34 could be employed as an alternative for the removal of dyes and colorants from aqueous solutions.

Solvent impregnated resin prepared using ionic liquid Cyphos IL 104 for Cr(VI) removal

Ionic liquid (IL) trihexyl (tetradecyl) phosphonium bis 2,4,4-trimethylpentylphosphinate (Cyphos IL 104) was impregnated on XAD–7 resin. The solvent impreganated resin (SIR) was prepared and applied in Cr(VI) removal. The morphology and the thermal stability of the resins were explored. The effects of equilibrium time and initial pH value on Cr(VI) adsorption were investigated. Adsorption isotherm, separation and desorption of the SIR, and selectivity of SIR were also explored. The results show that Cyphos IL 104 exists in the inner XAD-7 resin, and the optimum pH value range of the SIR for Cr(VI) extraction is 0 to 2. When NaOH used as desorption solution, the Cr(VI) can be effectively desorbed from the SIR.

A novel bentonite-based adsorbent for anionic pollutant removal from water

A novel adsorbent, HO-CaBen, was prepared by the modification of bentonite, which shows good potential as a cheap and effective adsorbent for anionic contaminants removal from aqueous solutions. The adsorbent HO-CaBen was characterized by XRD and FTIR. The effects of equilibrium time, pH and temperature on adsorption some typical anionic contaminants were studied by the batch adsorption process. The adsorption capacities for fluoride, phosphate, Orange II, and SDBS are 50.07, 29.1, 239.5, and 298.5mgg−1, respectively. These values are higher than those reported for low-cost adsorbents. The adsorption mechanism of the anion on HO-CaBen is anion/OH− exchange reaction and is verified by theoretical calculation results. These results indicated that HO-CaBen was a promising adsorbent for anion removal from wastewater treatment by bentonite.

Sol–gel derived poly(vinyl alcohol)-3-(2-aminoethylamino) propyl trimethoxysilane: Cross-linked organic–inorganic hybrid beads for the removal of Pb(II) from aqueous solution

This manuscript reports sol–gel derived cross-linked poly(vinyl alcohol) (PVA)-3-(2-aminoethylamino) propyl trimethoxysilane (AEAPTMEOS) beads with low degree of swelling as a new adsorbent for the removal of Pb(II) from aqueous solution. Beads were prepared by condensation polymerization followed via acid-catalyzed sol–gel process in presence of non-ionic surfactant. Cross-linking was achieved by glutaraldehyde. Presence of –NH/–NH 2 groups in beads provide active sites for Pb(II) adsorption, and were responsible for high adsorption capacity. SEM/TEM studies confirmed the spherical and rough surface morphology, which was changed after Pb(II) adsorption. For the removal of Pb(II) in aqueous solution, effect of equilibrium time, temperature, pH, adsorbent dose and adsorbate concentration were investigated in batch process. Pseudo-first- and pseudo-second-order kinetics were also evaluated. The equilibrium adsorption followed Langmuir and Freundlich isotherms. Thermodynamic parameters such as Δ G°, Δ H° and Δ S° revealed endothermic and spontaneous adsorption. Monolayer adsorption capacity ( Q 0) value for the developed PVA-AEAPTMEOS beads was 67.56 mg g −1 at pH: 5.0, much higher as compared to other adsorbents reported in literature. Desorption studies also suggested that cross-linked PVA-AEAPTMEOS beads can be effectively utilized for the removal of Pb(II) from wastewater.

Comparison absorption of new methylene blue dye in zeolite and nanocrystal zeolite

Mordenite and mordenite nanocrystal, were employed as effective adsorbents for new methylene blue (NMB) from an aqueous solution. The adsorption kinetics was investigated. The adsorption capacity of mordenite nanocrystal zeolite for NMB dye is more than that of the mordenite zeolite. Kinetic and adsorption isotherm studies demonstrate that the adsorption follows the pseudo second-order kinetics. The intraparticle diffusion rate coefficient values at 25 °C obtained by using the Morris–Weber equation showed that new methylene blue reached equilibrium in mordenite nanocrystal faster than in mordenite adsorbent. The effects of equilibrium time, solution pH and sorption temperature were examined. Solution pH will affect the adsorption behavior of mordenite and mordenite nanocrystal. Higher solution pH results in higher adsorption capacity. The results show that adsorption capacity dye increases in lower temperature.

Adsorption of methylene blue and orange II onto unmodified and surfactant-modified zeolite

Adsorption of cationic methylene blue and anionic orange II onto unmodified and surfactant-modified zeolites was studied using a batch equilibration method. The effects of equilibrium time, solution pH, and sorption temperature were examined. The results suggested that 2% sodium dodecyl benzenesulfonate (SDBS)- and 3% sodium dodecyl sulfate (SDS)-modified zeolites had higher adsorption capacities for methylene blue than the unmodified zeolite, while 2% cetylpyridinium bromide hexadecyl (CPB)- and 2% hexadecylammonium bromide (HDTMA)-modified zeolites were the best adsorbents for orange II. The adsorption conditions were optimized, and the mechanisms of adsorption are briefly discussed.

Uptake monitoring of anilines and phenols using modified zeolites

Uptake monitoring of a group of environmentally important phenolic and aniline compounds including aniline, phenol, 4-methylaniline, 4-aminophenol, 2-aminophenol, 4-nitrophenol, 2-nitrophenol and 2-methyl-4-nitrophenol was carried out using micellar electrokinetic capillary chromatography. For the removal of tested pollutants, the natural zeolites natrolite and clinoptilolite were examined in which the latter showed better uptakes ranging from 45 to 64% of pollutants from aqueous solution in 4 h. Modification of zeolites with cyclodextrins (CDs), especially, α-CD, considerably improves the uptake efficiency to 65–74% for clinoptilolite. The effects of equilibrium time, type and concentration of CDs were also investigated. The versatility of micellar electrokinetic capillary chromatography was shown for this type of study owing to its speed, resolution ability, and simplicity.

1-(2-pyridylazo)-2-naphthol (PAN) as extractant in solid—liquid extraction of some trivalent rare earth elements

In the present paper, solid-liquid extraction behaviour of RE(III) (RE  La, Ce, Pr, Nd, Sm, Gd, Dy and Yb) by the use of 1-(2-pyridylazo)-2-naphthol (PAN, HL) as an extractant in paraffin (m.p. 48 ∼ 50°) has been investigated at 80 ± 0.07°. The effect of equilibrium time, pH of aqueous phase, concentration of extractant in paraffin and solid diluent as well as buffer solution used on the extraction efficiency of RE(III) have been discussed. The extraction reacton is RE 3+ + 2HL (o) + Cl − ⇌ REL 2Cl (o) + 2H +

Solvent extraction of cerium/III/ with 1-/2-pyridylazo/-2-naphthol from perchloric acid media

A study on solvent extraction of cerium/III/ ion with 1-/2-pyridylazo/-2-naphthol /PAN or HL/ in chloroform from perchloric acid solution is described. The effect of equilibrium time, the pH of the aqueous phase and the concentration centration of extractant in organic phase on the extraction efficiency of cerium/III/ has been studied. The results show that the mechanism of extraction reaction is 3Ce/aq/3+ + 3HL/o/ ⇌ CeL3/o/ + 3H+/aq/