Decrease In Sorption Capacity Research Articles

Кинетика сорбции нефти материалом на основе листового опада

Studies of leaf litter as a sorption material with respect to oil at various temperatures have been carried out. It has been revealed that with process temperature increasing, the samples sorption capacity decreases. The oil sorption mechanism has been studied. It has been shown that the active sorption time was in the interval from 60 to 600 seconds. It has been proved that at the time of oil and sorption material contact for more than 600 seconds, the desorption process began. Kinetic dependencies of oil absorption by the proposed sorption material have been constructed and analyzed. The reaction order determination by a graphic method has showed that obtained functions with a high degree of correlation can be attributed to first-order heterogeneous reactions. Have been calculated thermodynamic parameters confirming the absence of a chemical reaction between oil and leaf litter. The carried out researches determine the most acceptable parameters of oil sorption by material based on leaf litter.

Synthesis and adsorption characteristics of grafted hydrazinyl amine magnetite-chitosan for Ni(II) and Pb(II) recovery

The sorption properties of a functionalized magnetic chitosan sorbent have been investigated for the recovery of Ni(II) and Pb(II) from aqueous solutions. This material was prepared by one-pot co-precipitation of chitosan with formation of magnetic core, followed by a series of grafting steps to immobilize hydrazinyl amine derivative at the surface of chitosan layer. The physico-chemical characteristics of this composite material were investigated using FTIR, XRD, XPS, thermogravimetric, titration, elemental analyses. In a second step, the sorbent was tested for heavy metal sorption on synthetic solutions through the study of pH effect, sorption isotherms and uptake kinetics, selective sorption (in function of pH), metal desorption and sorbent recycling. Sorption isotherms were modeled using the Sips equation while the uptake kinetics was fitted by the pseudo-second order rate equation. The sorption capacity reached 4.3 mmol Ni g−1 and 2.5 mmol Pb g−1 but the sorbent was more selective to Pb(II) over Ni(II), especially in acidic conditions. The decrease in sorption capacity at the fifth cycle does not exceed 8%. In the final step of the study, the sorbents were successfully applied for metal recovery from multi-metal synthetic solution and from a contaminated stormwater collected in a local mining area.

Sorption of Eu(III) on Fe–montmorillonite relevant to geological disposal of HLW

Abstract Montmorillonite (Mt) is the major clay mineral of bentonite, which is the candidate buffer material in the engineered barrier system for geological disposal of high level waste (HLW). The alteration of Mt due to its interaction with carbon steel (overpack) can produce Fe–Mt. In order to understand the basic properties of Fe–Mt, the sorption studies using Eu(III) are reported here. For this, Fe(III)–Mt was prepared by conventional cation exchange method using FeCl3 with Na–Mt. The obtained Fe(III)–Mt was then reduced to Fe(II)–Mt using ascorbic acid. Both the samples were characterized based on their X-ray diffraction, Fourier transform infrared spectra, cation exchange capacity and specific surface area. The batch sorption studies of Eu(III) were conducted for both Fe(III)–Mt and Fe(II)–Mt as a function of pH (3–10), ionic strength (0.001 M–1 M) and Eu(III) concentration (10−8–10−3 M). The distribution coefficient (Kd) was found to be higher for Fe(III)–Mt compared to Fe(II)–Mt and Na–Mt. The sudden increase in sorption in the pH range 4.5–6 and remaining constant beyond it indicates ion exchange mechanism at pH<4.5, with surface complexation mechanism dominating the sorption at pH>4.5. This is further corroborated by ionic strength dependent sorption data which shows decrease in sorption capacity of Fe–Mt with increasing ionic strength at low pH, but remaining more or less unchanged at higher pH. Eu(III) adsorption isotherm on Fe–Mt increased linearly with [Eu(III)] reaching saturation at 10−5 M and 10−4 M for Fe(III)–Mt and Fe(II)–Mt, respectively. The amount of iron released from Fe–Mt and Fe(II)/Fetotal during sorption were estimated to understand the effect on Eu(III) sorption behaviour by release of interlayer iron in Fe–Mt.

Design and synthesis of core–shell Fe3O4@PTMT composite magnetic microspheres for adsorption of heavy metals from high salinity wastewater

In this study, a novel magnetic nanoparticles (MNP) modified by an organodisulfide polymer (PTMT) was designed for adsorption of heavy metals (Hg(II), Pb(II) and Cd(II)) from simulated coal chemical high salinity wastewater. The MNP-PTMT nano-composite was synthesize and characterized by SEM, TEM, FTIR, BET, VSM, TGA and XRD. The results indicate that the wanted MNP-PTMT magnetic nanoparticles were successfully obtained by modification. Adsorption experiments were systematically carried out to evaluate the performance of the obtained nanoparticles and to build up the adsorption models. The results demonstrate that the adsorption kinetic and isotherms thermodynamic followed the pseudo-second-order model and the Freundlich equation, respectively. In the presence of the inorganic salt in high salinity wastewater, the adsorption efficiency of MNP-PTMT for heavy metals was still excellent. The magnetic adsorbent could be recovered from aqueous solution by an external magnetic field in 20s and the subsequent regeneration of Hg(II)/Pb(II) loaded MNP-PTMT can be efficiently achieved by using EDTA-2Na solution as desorbent. The novel MNP-PTMT nanoparticles could be used reproductively for five times without apparent decrease in sorption capacity.

Improving Physical Adsorption of CO2 by Ionic Liquids‐Loaded Mesoporous Silica

AbstractCO2 sorption capacities of the neat and silica‐supported 1‐butyl‐3‐methylimidazolium‐based ionic liquids (ILs) were measured under atmospheric pressure. The silica‐supported ILs were synthesized by the impregnation‐vaporization method and charactrized by N2 adsorption/desorption and thermogravimeteric analysis (TGA). Evaluation of the effects of influential factors on sorption capacity demonstrated that by increase of the temperature, flow rate, and the weight percentage of ILs in sorbents, the sorption capacity decreases. Among the sorbents, [Bmim][TfO] and SiO2‐[Bmim][BF4](50) had the highest capacity. By increasing the IL portion in SiO2‐[Bmim][BF4], the selectivity for CO2 to CH4 could be improved. The CO2‐rich sorbents could be easily recycled.

Uranium and europium sorption on amidoxime-functionalized magnetic chitosan micro-particles

Magnetic chitosan particles were successfully modified by amidoxime-grafting (as evidenced by FTIR analysis, SEM-EDX analysis, elemental analysis, X-ray diffraction (XRD), thermogravimetric analysis and titration). The effect of pH was investigated showing optimum sorption at pH 4 for U(VI) and pH 5 for Eu(III). Uptake kinetics are relatively fast: the equilibrium was reached within 60–90 min; and the kinetic profiles were preferentially fitted by the pseudo-second order rate equation. Sorption isotherms are equally fitted by the Langmuir and the Sips equations; under optimal conditions maximum sorption capacity reaches 1.5 mmol U g−1 and 2.47 mmol Eu g−1. In bi-component solution, at pH close to 4.9, uranyl is enriched on the sorbent (higher selectivity coefficient) while maintaining high sorption capacities. The selectivity for Eu(III) sorption is higher at pH 2.3 but at the expense of a decrease in sorption capacities. Metal ions can be readily and fast desorbed using 0.5 M HCl solutions: 30–90 min are sufficient for achieving the complete desorption of U(VI) and about 95% of Eu(III) desorption. Sorption and desorption performances are maintained almost constant over 5 cycles of sorption/desorption: the sorbent can be efficiently recycled. Uranium was successfully recovered from alkaline leachate of a sedimentary dolostone ore material.

Sorption capacity and mechanism of Cr3+ on tobermorite derived from fly ash acid residue and carbide slag

In this study, tobermorite was successfully synthesized from two kinds of industrial wastes by single step hydrothermal method. The structural and morphological changes during synthesis show that well-crystallized tobermorite can be obtained within 6h at 180°C in this system. The carbon impurities lead to a longer synthesis time and lower crystallinity of tobermorite. The tobermorite displays attractive adsorption capacity for Cr3+ (4.87mmol/g), which is 2–3 times higher than common clay minerals. Meanwhile, Cr3+ adsorption causes the exsolution of structural Ca2+ in tobermorite channels, leading to the damage of crystallinity and decrease in sorption capacity of adsorbent. Therefore, better crystallization of tobermorite is helpful to achieve higher sorption capacity for Cr3+. These results indicate tobermorite can be used in industrial processes to adsorb heavy metals from wastewater.

Phosphate recovery from treated municipal wastewater using hybrid anion exchangers containing hydrated ferric oxide nanoparticles

AbstractBACKDROUNDThis study presents the evaluation of two ion exchangers (granular and fibrous) impregnated with nanoparticles of hydrated ferric oxide (HFO) as selective sorbents for phosphate recovery from aqueous solutions. The hybrid impregnated anion exchangers combine the durability and mechanical strength of a polymeric weak base anion exchange resin with the high sorption affinity of HFO towards phosphate species. Dynamic experiments were carried out and data obtained were fitted to a well‐known fixed‐bed sorption model.RESULTSThe theoretical sorption capacities reported by the Thomas model were in good agreement with the breakthrough experimental capacities determined from the sorption data. The sorption capacity decreased when using wastewater treatment plant secondary effluents in comparison with synthetic water mainly owing to the presence of organic matter and suspended solids. The phosphate sorbed on the impregnated ion exchangers was efficiently desorbed by using a 0.5 mol L‐1 sodium hydroxide solution, reporting up to 90% of recovery.CONCLUSIONThe reusability of sorbents was evaluated through five sorption–desorption working cycles. Fiban‐As was able to operate up to three consecutive cycles with good sorption performance while a significant decrease of sorption capacity after the first cycle was observed for FO36 resin. © 2017 Society of Chemical Industry

Design, characterization and evaluation of hydroxyethylcellulose based novel regenerable supersorbent for heavy metal ions uptake and competitive adsorption

Hydroxyethylcellulose succinate-Na (HEC-Suc-Na) was designed and evaluated for removal of some heavy metal ions from aqueous solution. Pristine sorbent HEC-Suc-Na was thoroughly characterized by FTIR and solid-state CP/MAS 13C NMR spectroscopy, SEM-EDS and zero point charge analyses. Langmuir isotherm, pseudo second order kinetic and ion exchange models provided best fit to the experimental data of sorption of metal ions. Maximum sorption capacities of supersorbent HEC-Suc-Na for sorption of heavy metal ions from aqueous solution as calculated by Langmuir isotherm model were found to be 1000, 909.09, 666.6, 588 and 500mgg−1 for Pb(II), Cr(VI), Co(II), Cu(II) and Ni(II), respectively. Competitive sorption of these heavy metal ions was carried out from galvanic and nuclear waste water simulated environment. The negative values of ΔG° and ΔH° indicated spontaneity and exothermic nature of sorption. The sorbent was efficiently regenerated with no significant decrease in sorption capacity after five cycles.

Oil/water mixtures and emulsions separation of stearic acid-functionalized sponge fabricated via a facile one-step coating method

Abstract Superhydrophobic and superoleophilic sponge was prepared by facile dip coating in a stearic acid (SA) solution and subsequent heat treatment. The obtained sponge exhibits excellent superhydrophobic stability and selectively sorption ability for oil pollutants on water surface. Also, the sponge is capable of separating huge amounts of oils from water continuously via a vacuum system and oil droplets in oil-in-water emulsions. After the separation by the coated sponge, the transparency for the emulsions (n-Hexane-in-water and toluene-in-water) can increase to over 80% from below 14.7%. The oil sorption capacity of as-prepared sponge for various types of oils and organic solvents can reach 17.4–41.6 times of its own weight, and the absorbed oils are easy to be recovered by a simple squeezing process. Moreover, the recovered sponge can repeatedly absorb/desorb the oils for at least 100 times, demonstrating slightly decrease in sorption capacities and hydrophobicity. The proposed approach for fabricating superhydrophobic sponges is simple and inexpensive so that the as-prepared sponge has great potential as an efficient sorbent in oily wastewater filtration and oil spill clean-up.

Grafting of arginine and glutamic acid onto cellulose for enhanced uranyl sorption

The grafting of arginine and glutamic acid on cellulose (through an intermediary step of chlorination) allows improving uranyl sorption of the biopolymer. The sorbents (Arg-Cell and Glu-Cell) were characterized by elemental analysis, FTIR spectrometry, XRD, SEM-EDX analysis and TGA. The sorption efficiency increases with pH; this can be attributed to the deprotonation of carboxylic acid and amine groups and to the formation of polynuclear hydrolyzed uranyl species. Sorption isotherms (fitted by the Langmuir equation) show sorption capacities at saturation of the monolayer of 147 and 168 mg U g−1 for Arg-Cell and Glu-Cell, respectively (compared to 78 mg U g−1 for raw cellulose); maximum sorption capacities at equilibrium (experimental values) reach 138, 160 and 73.4 for Arg-Cell, Glu-Cell and cellulose, respectively. Uranyl sorption is endothermic and is spontaneous for amino acid derivatives of cellulose (contrary to exothermic for cellulose). Uptake kinetics for the different sorbents are fitted by the pseudo-second-order rate equation. Uranium can be desorbed using sulfuric acid solutions, and the sorbents can be recycled for a minimum of five cycles of sorption/desorption: the decrease in sorption capacities at the fifth cycle does not exceed 13%.

Effect of KOH treatment on bituminous coal for the effective removal of Basic Blue 41 dye from aqueous solutions

Activated carbons (ACs) were produced from Zonguldak region bituminous coal using physical and chemical techniques and evaluated for the removal of a textile dye, Basic Blue 41 from aqueous solutions. The color removal performance of ACs prepared by physical activation (PAC), chemical activation with KOH (CAC), and the commercial AC were compared; and the effects of adsorbent preparation method, temperature, and initial dye concentration on adsorption were studied. BET surface areas of the PAC, AC, and CAC were determined as 52.6, 824, and 1,312 m2 g−1, respectively. Micropore volume of PAC determined by DR method was 0.02 cm3 g−1, whereas AC and CAC have values of 0.42 and 0.57 cm3 g−1. Thermal treatment with KOH resulted in enhancement of the porosity characteristics, particularly in micropores, and the surface area of the CAC samples. The batch adsorption experiments were carried out isothermally at 25–35°C. The values for the adsorption capacity Q0, determined from the Langmuir model at 25, 30, and 35°C were 96.4, 52.1, 54.7 mg g−1 for PAC; 262.5, 283.3, 293.3 mg g−1, for AC; and 420.2, 427.4, 460.8 mg g−1 for CAC, respectively. The increase in adsorption capacity with an increase in temperature for BB 41 onto CAC and AC indicated an endothermic chemisorption process, which was attributed to increased surface coverage at higher temperature and creation of reactive and active sites. For BB 41 adsorption onto PAC, the decrease in sorption capacity with increasing temperature indicated the exothermic behavior of the sorption process that is related to physisorption. The adsorption capacity of the obtained samples was found in the order of CAC > AC > PAC. Among the AC samples prepared by different methods, the highest value of the adsorption capacity obtained was 460.8 mg g−1 at 35°C for CAC. Kinetic data were adequately represented by the pseudo-first-order kinetic model. AC prepared from coal by CAC treatment was shown to be an effective adsorbent for the removal of BB 41.

Decontamination of Cesium From Contaminated Water Using a Selective Adsorbent and Magnetic Separation

Radioactive cesium was released from nuclear accidents such as Fukushima and Chernobyl's nuclear power plant accident. The released cesium contaminated the water and soil environment around the accident area. Common environmental technologies for water and soil could not be used for the cesium-contaminated environment due to several reasons. The radioactive cesium exists as in a trace amount and with other common cations such as calcium and sodium. The coexisting cations interfere the removal of cesium and increase the final waste. Magnetic separation combined with adsorption technology can be applicable to the removal of radioactive cesium from water environments. In current study, a selective adsorbent for cesium, i.e., silicotitanate, was synthesized and tested for cesium selectivity. The cesium-selective adsorbent was magnetized and separated from water using a superconducting magnet. The decrease of sorption capacity was evaluated after magnetization. The cesium selectivity was sustained after the magnetization. The removal efficiency of magnetized silicotitanate was highly dependent on the magnetic field and magnetizing method. Complete removal of the magnetized adsorbent was achieved by a superconducting magnet, indicating that a superconducting magnet system with magnetized silicotitanate can be an alternative for water treatment from nuclear accident sites.

Selective absorption of heavy metals by soil and humic acids at different pH levels

Studying processes of sorption-desorption of heavy metals from soil and its individual components allow to predict long-term effects under conditions of multielement contamination. Cations of heavy metals are showing competitive relationship due to their specific adsorption by components of the soil absorption complex, in particular humic acids. Interaction of chernozem podzolized heavy loam, isolated preparation of humic acids and soil residue after its removal with the solution which contain sulphates of Zn, Cd, Ni, Co and Cu in equal ratio were simulated at different pH levels. The task of research was to compare selective absorption of some heavy metals in soil and humic acids at pH values from 3 to 9. The experiment was performed by mixing 10 g of soil material or 0.1 g of humic acid with 100 ml of buffer solution, adding 10 ml 0.01 n equal mixture of Cd, Zn, Ni, Co, Cu and 2-hour exposure. Humic acids were extracted from this soil by 0.1 n NaOH after decalcification using 0.05 n H2SO4. Crystalline Copper sulphate, Zinc, Nickel, Cobalt, Cadmium were used to prepare the solution level of heavy metals. Ammonium acetate-buffer solutions with different pH (3.0, 5.0, 7.0, 9.0) were obtained by varying the ratio CH3СOOH and NH4OH. The experiment showed that competitive relationship between heavy metal in soil and humic acids. Copper has the highest specificity adsorption, Cobalt – the smallest. Under acidic and strongly acidic reaction content of Zn, Cd, Ni in equilibrium solution is close enough. The absorption of copper was increased by 50 % from strongly acidic to neutral reaction. Under alkaline conditions Cobalt and Copper were practically absent in the solution. Has been found that the absorption of heavy metals by soil decreases in sequence: Cu, Zn > Cd, Ni > Co. The selectivity of the absorption of heavy metals by humic acids was less marked, but the ability to sorption has the similar sequence: Cu > Zn > Ni > Cd > Co. The residue of soil after removal of humic acids has a high affinity for copper ions, which was absorbed twice from each other metals. Has been proved experimentally that selective adsorption of heavy metals in soil significantly depends on the pH, decreasing under acidic and strongly acidic conditions where hydrogen is successfully competing with them for exchange places in soil absorption complex. Deviation from the equivalent absorption (20 %) of each heavy metal in soil accounted for 15.0–26.0 % in acidic pH and 1.6–45.4 % in alkaline pH. After the interaction of heavy metals with humic acids in the most acidic medium fluctuations content elements in the equilibrium solution was 15.7–25.3 %, while the highest pH 11.0–26.7 %. Overall, the decrease of sorption capacity for humic acids elements can be placed in the following order: Cu > Zn > Ni > Cd > Co. This sequence is saved by a narrow ratio solution: adsorbent. Thus, under condition of polyelement contamination migration of Cobalt in soil may be more intensive than Zink, Cadmium, Nickel and a lot more than Copper, especially in alkaline pH.

Improving Stability of Zeolites in Aqueous Phase via Selective Removal of Structural Defects.

Missing silicon-oxygen bonds in zeolites are shown to be the cause for structural instability of zeolites in hot liquid water. Their selective removal drastically improved their structural stability as demonstrated using zeolite beta as example. The defects in the siloxy bonds were capped by reaction with trimethylchlorosilane, and Si-O-Si bonds were eventually formed. Hydrolysis of Si-O-Si bonds of the parent materials and dissolution of silica-oxygen tetrahedra in water causing a decrease in sorption capacity by reprecipitation of dissolved silica and pore blocking was largely mitigated by the treatment. The stability of the modified molecular sieves was monitored by (29)Si-MAS NMR, transmission electron micrographs, X-ray diffraction, and adsorption isotherms. The microporosity, sorption capacity, and long-range order of the stabilized material were fully retained even after prolonged exposure to hot liquid water.

Easily prepared and stable functionalized magnetic ordered mesoporous silica for efficient uranium extraction

Functionalized magnetic Fe3O4@SiO2 composite nanoparticles were prepared by simply embedding iron oxide nanoparticles into MCM-41 through one-step synthesis process, followed by aminopropyls grafting on the mesopore channels, aiming to efficiently and conveniently uptake U(VI) from aqueous solution. The resultant material possesses highly ordered mesoporous structure with large surface area, uniform pore size, excellent thermal stability, quick magnetic response, and desirable acids resistance, confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), N2 adsorption/ desorption experiments, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Detailed U(VI) sorption test indicated that this material is indeed an effective U(VI) sorbent with fast sorption kinetics of less than 2 h, large sorption capacity of 160 mg/g at pH 5.0±0.1, and desirable selectivity towards U(VI) ions over a range of competing metal ions. The absorbed U(VI) can be easily desorbed by 0.01 mol/L or more concentrated HNO3 solution, and the reclaimed sorbent can be reused with no obvious decrease of sorption capacity even after 4 sorption-desorption cycles. The present results suggest the vast opportunities of this kind of magnetic composite on the solid-phase extraction of U(VI).

Polyacrylonitrile-based fiber modified with thiosemicarbazide by microwave irradiation and its adsorption behavior for Cd(II) and Pb(II)

A novel thiosemicarbazide modified adsorbent (PANMW–TSC) based on polyacrylonitrile fiber was successfully synthesized under microwave irradiation, which was applied for the uptake of Cd(II) and Pb(II) from aqueous solution subsequently. Microwave irradiation method is a new approach to achieve the modification and it turns out that just a 30min process is enough for the anchoring of functional groups in the fiber matrix. The surface characterization was performed by fourier transform infrared spectroscopy (FT–IR), scanning electron microscopy (SEM) elemental analysis (EA) and thermogravimetric analysis (TGA), indicating that the modification was successfully accomplished. Batch adsorption experiments including equilibrium isotherms, kinetics and the effects of pH and temperature on the adsorption of Cd(II) and Pb(II) were systematically studied. Among three kinetic models, the pseudo-second-order kinetic model provides the best correlation for the process. The nonlinear resolution of the Langmuir isotherm equation has been found to show the closest fit to the equilibrium date. Thermodynamic parameters, involving △G, △H and △S were also calculated from graphical interpretation of the experimental data, which suggest that metal ions adsorption onto PANMW–TSC fibers is spontaneous and exothermic. Regeneration of PANMW–TSC fibers loaded with metal ions was efficiently done with 0.5M HNO3, by which the investigated adsorbent could be used reproductively for five times with a small decrease in sorption capacity. The feasible preparation of PANMW–TSC fibers with high adsorption capacities opens a new perspective in the potential application for wastewater treatment.

Influence of Dissolved Organic Matter on Sorption and Desorption of 1,2,4-trichlorobenzene and 1,2,4,5-tetrachlorobenzene onto Wood Char

ABSTRACTSorption and desorption of 1, 2, 3-trichlorobenzene (TCB) and 1,2,4,5-tetrachlorobenzene (TeCB) onto wood char prepared from maple wood shavings heated at 500°C were studied in the presence of dissolved organic matter (DOM), including humic acid (HA), L-malic acid (L-MA), and peptone. Compared to TCB, TeCB exhibited more nonlinear and stronger sorption onto wood char. Nonlinearity of the sorption isotherms increased in the presence of DOM. The presence of HA enhanced the sorption capacity and desorption hysteresis of TCB and TeCB on wood char mainly due to the strong sorption of HA on wood char surface. Moreover, there were positive relations between Kd values of TCB and TeCB and the HA concentration (p < 0.01). In contrast, peptone reduced the sorption capacity and increased the sorption reversibility because of the partition of TCB and TeCB in peptone solution. L-MA at 50-200 mg·L−1 also leads to a decrease in sorption capacity and irreversibility attributed to solubilization, although the sorbed L-MA on the wood char surface can slightly increase TCB and TeCB sorption. At the same concentration, peptone leads to a higher decrease in TCB sorption than L-MA. Also, negative correlations were found between Kd values of TCB and TeCB and the L-MA and peptone concentration (p < 0.01). Our results may help to understand the different impacts of DOM on the transport and fate of halogenated aromatic hydrocarbons in aquatic environments polluted with chars.

Metals (Mg, Sr and Al) modified CaO based sorbent for CO2 sorption/desorption stability in fixed bed reactor for high temperature application

Modified sorbents – produced by adding compounds of Mg2+, Sr2+ and Al3+ to calcium oxide – have been tested in terms of their CO2 sorption/desorption performance in a fixed bed reactor at high temperatures. In particular this study focuses on the stability of the sorbents as well as the sorption capacity, both of which are important factors when selecting sorbents. X-ray diffraction (XRD) and scanning electron microscope (SEM), coupled with energy dispersive X-ray spectroscopy (EDX), were used for characterization of the modified sorbents. XRD results indicated that samples produced using the wet mixing process and those produced using the hydration with wet mixing process, contained MgO–CaO, Ca0.2Sr0.8O–CaO and Ca12Al14O33–CaO phases, respectively.The operating conditions have been investigated and results showed that the CaO showed the highest sorption capacity (0.571gCO2/gsorbent) when compared with MgO, SrO and Al2O3 at temperature of 600°C. In terms of sorption capacity performance for sorbents produced by the CaO hydration and wet mixing method, Mg-CaO-HW showed the best sorption/desorption stability for more than 10 cycles (CO2 sorption capacity of 0.259 for 1st cycle to 0.252gCO2/gsorbent for the 10th cycle). Al-CaO-HW and Sr-CaO-HW exhibited a decrease in sorption capacity due to the sintering as confirmed by SEM images (0.257 and 0.286gCO2/gsorbent for 1st cycle dropping to 0.243 and 0.251gCO2/gsorbent for 10th cycle resulting in decreasing approximately of 5.45% and 12.24%, respectively).

Removal of phosphate from industrial wastewater using uncalcined MgAl-NO3 layered double hydroxide: batch study and modeling

In this study, the sorption ability of nitrate containing MgAl layered double hydroxide as an anion-exchanger to remove phosphate from a real effluent was investigated. The LDH material was prepared via coprecipitation method and characterized by X-ray diffraction, SEM, Fourier Transform Infrared, BET surface area, and pHzpc. The effect of physico–chemical key parameters on phosphate removal, such as sorbent dosage, solution pH, initial concentration, and contact time, has been studied in batch mode. The sorption reached equilibrium within 30 min. Furthermore, the sorption mechanism of phosphate onto MgAl-NO3 LDH is a combination of both anion-exchange and electrostatic attraction. The equilibrium 8 data were tested using Langmuir, Freundlich, and Dubinin–Radushkevich isotherms. The results show that the Langmuir isotherm describes sufficiently the sorption equilibrium, offering a maximum sorption capacity of 64.10 mg/g. Sorption kinetic follows accurately pseudo-second-order reaction. The sorbent reusability shows that regenerated LDH can be reused in subsequent sorption–regeneration cycles with a slight decrease in sorption capacity.