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Dichromate and arsenate anion removal by PEI microgel, cryogel, and bulkgel

Nahit AKTAŞ

Makale | 2021 | Journal of Environmental Chemical Engineering9 ( 2 )

Among the various metal ions, chromate (Cr(VI)) and arsenate (As(V)) are the two most hazardous toxic ion species and are found in nature in the form of dichromate and arsenate anions. In this investigation, polyethyleneimine (PEI)-based hydrogels were prepared with microgel, cryogel, and bulkgel morphologies employing glycerol diglycidyl ether as a crosslinker. The prepared PEI-based hydrogels were used to remove dichromate and arsenate anions from aqueous media. PEI microgel, cryogel, and bulkgels weighing 50 mg of each adsorbed 84.7 /- 0.8, 76.5 /- 5.2, and 108.9 /- 2.4 mg.g(-1) of dichromate anions and 15.9 /- 0.7, 45.4 /- 1.9, . . .and 79.2 /- 11.6 mg.g(-1) of arsenate anions in 30, 120, and 240 min, respectively. The dichromate and arsenate anions adsorption of PEI-based hydrogels were found to fit to the pseudo-second-order kinetic, and nonlinear Langmuir isotherm models, respectively with higher R-2 values. The highest distribution coefficient (K-d) value of PEI-based hydrogels for dichromate adsorption was obtained on the cryogel forms of PEI as 1.89 /- 0.05. Likewise, the highest K-d value for the arsenate adsorption was calculated on PEI-based bulkgels as 0.46 /- 0.01. The thermodynamic parameters of PEI based hydrogels in the adsorption of dichromate and arsenate anions e.g., Delta G (all negative (except for the arsenate adsorption by PEI microgels), and Delta H that is around 2-10 kJ.mol(-1), and Delta S what is around 0.01-0.02 kJ.mol(-1). K-1 were calculated. The reusability studies showed that PEI-based hydrogels can be used for at least 5 consecutive adsorption-desorption cycles with almost 70 ?nion removal efficiency after the fifth cycle Daha fazlası Daha az

Renewable-based treatment solution of Reactive Blue 21 dye on fly ash as low-cost and sustainable adsorbent

Mehmet KOBYA

Makale | 2024 | Journal of Chromatography A1715

This study investigated the removal of Reactive Blue 21 (RB 21) dye from aqueous solutions by adsorption, evaluating the waste fly ash (FA). The effects of the parameters, such as initial dye concentration (100–750 mg/L), initial pH (2.0–8.0), adsorbent dose (1.0–4.0 g/L), and temperature (298–323 K) on the adsorption process were investigated. The optimum initial pH value was 2.0 for the highest RB21 dye removal (75.2 mg/g). At optimized conditions (pH 2.0, an adsorbent dosage of 1.0 g/L, a dye concentration of 750 mg/L, and an equilibrium time of 72 h), the highest adsorption capacity was found to be 105.2 mg/g. Moreover, the resu . . .lts of the kinetic studies fitted the pseudo-second-order kinetic model. Equilibrium data were best represented by the Langmuir isotherm model, with a maximum monolayer adsorption capacity of 103.41 mg/g at 323 K. ΔGads0 values were negative and varied from 11.64 to 9.50 kJ/mol in the temperature range of 298–323 K, the values of enthalpy (ΔHadso) and entropy (ΔSadso) of thermodynamics parameters were calculated as 37.62 kJ/mol and 86.67 J/mol K, respectively, indicating that this process was endothermic. Furthermore, the adsorbent costs for powdered activated carbon (PAC) and FA to remove 1 kg of RB 21 dye from aqueous solutions are calculated as 2.52 U.S. and 0.34 U.S. , respectively. It is seen that the cost of FA is approximately 7.4 times lower than PAC. The results showed that FA, a low-cost industrial waste, was promising for the adsorption of RB 21 from aqueous solutions. Keyword: adsorption; fly ash; isotherm; kinetics; reactive blue 2 Daha fazlası Daha az

Urea Uptake and Release by Novel Macrogels from Dimethylacrylamide

Nahit AKTAŞ

Makale | 2019 | Communications in Soil Science and Plant Analysis50 ( 18 )

A novel macrogels poly(N,N-Dimethylacrylamide) (p(DMAAm)) and its derivatives were synthesized from DMAAm for use in urea uptake and release. p(DMAAm) surface was modified by NaOH and HCl to obtain p(DMAAm)/NaOH and p(DMAAm)/HCl, which are negatively and positively charged, respectively. The dynamic swelling behaviors, water retention and pH sensitivities of the macrogels were studied. It was found that all macrogels exhibited the equilibrium swelling ratio (SR) in the range 1068-1451%. Swelling kinetics showed that the macrogels possessed Fickian diffusion behavior while the diffusion coefficient of the macrogels varied from 1.41.1 . . .0(-5) to 2.53.10(-5) cm(2)/min. Furthermore, urea uptake capacity and controlled release properties of the macrogels were studied. The maximum urea uptake capacity at pH 6 for p(DMAAm), p(DMAAm)/HCl, p(DMAAm)/NaOH macrogels were obtained to be 76.7 mg/g, 88.2 mg/g, 110.5 mg/g, respectively. It was concluded that the Langmuir isotherm fits quite well the experimental data. To describe the urea release kinetics, experimental data recorded at different pH solutions were computed through common release models. At pH 8, the p(DMAAm)/NaOH showed the highest release among the three prepared macrogel. Consequently, the results demonstrated that synthesized novel macrogels had high swelling rate and ability of absorbing and releasing of urea at different medium conditions Daha fazlası Daha az

Preparation of molecularly imprinted PDMS elastomer for selective detection of folic acid in orange juice

Nahit AKTAŞ

Makale | 2019 | Applied Surface Science471 ( 31 )

Herein, it is reported an effective method to prepare novel molecularly imprinted polymers (MIP) on poly(dimethylsiloxane) (PDMS) elastomer via a combination of non-covalent imprinting approach and surface initiated reversible addition fragmentation chain transfer (SI-RAFT) polymerization for sensitive and selective detection of folic acid (FA). For this purpose, 2-(2-Methoxyethoxy) ethyl methacrylate (MEOMA), ethylene glycol dimethacrylate (EGDMA), azobisisobutyronitrile (AIBN), FA and dimethylsulfoxide (DMSO) were used as functional monomer, cross-linker, initiator, template molecule, and porogen, respectively. The adsorption beha . . .vior followed the Scatchard equation between FA and PDMS-MIP with a saturation adsorption capacity of 4.51 mg/g and pseudo-second-order kinetics with 60 min equilibrium adsorption time. Furthermore, PDMS-MIP elastomer was successfully applied for selective extraction and detection of FA from orange juice with sufficient recovery (95.5–100.5?and relative standard deviation less than 7.0?The limit of detection (LOD) for FA was found to be 0.0031 µg/mL with a linear range between 0.01 and 100 µg/mL and a correlation coefficient of 0.9997. Results showed the proposed method could easily, efficiently and selectively extracted FA from complex media. Note that this novel proposed method will open a new way to detect any selected molecules such as pesticide, protein, drug, etc. using molecularly imprinted PDMS elastomer materials Daha fazlası Daha az

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