Search

Dyes and heavy metals are typical pollutants causing environmental problems. In this study, the efficiency of GO and GO-EDTA used as adsorbents for Thioflavin T (TFT) and Co(II) metal ion removal from aqueous solution under optimum conditions was investigated. GO-EDTA was characterized by DR-UV/VIS, Raman spectra, FTIR and zero charge points (pHpzc) were determined using pH drift method. The maximum adsorption capacities (qM) of the adsorption process according to the Langmuir isotherm model, one of the isotherm models, refer to GO or GO-EDTA; It is 389.3178 mg g-1 and 1009.5300 mg g-1 for TFT dye, 736.9153 mg g-1 and 1304.3525 mg g-1 for Co(II) ion (pH=7, t= 150 min, 298 K). The kinetic data fit the pseudo-second order model quite well. In the desorption graph, TFT dye desorption was observed to be quite efficient, while the reason for the decrease in the desorption of Co(II) ion was considered to be the strong bond formed as a result of ion exchange at the -COONa end in the EDTA structure. It was supposed that p-p interactions with benzene rings in GO and GO-EDTA structure, hydrogen bonding with functional groups on the structure and electrostatic interactions as a result of ion exchange at the carboxylic acid ends were generally effective in the adsorption mechanism. In conclusion, it was shown that GO and GO-EDTA nanomaterials can be effectively used as advanced adsorbents instead of traditional adsorbents for the removal of organic and inorganic pollutants from aqueous solution. [ABSTRACT FROM AUTHOR]

In recent years, water pollution has become a major problem, especially due to the wastes discharged from different sectors without treatment. Among these, there are various paint wastes used by the textile, leather, paper and cosmetics sectors. Crystal violet (CV) is a widely known cationic dye and is often used as a colorant in industries. CV dye is known to be toxic to humans and animals at 1 ppb. For this reason, it is very important for environmental safety to treat industrial wastewater from crystal violet before discharge. This research aimed to evaluate the efficacy of two different montmorillonite-based nanoclays (B1 and B2) as a low-cost material for the removal of crystal violet dye from aqueous solutions. Structural characterizations of nanoclays were analyzed using FTIR and TGA methods. All parameters that could affect the CV adsorption process were optimized in a batch system. The effects of various factors (adsorbent dose, contact time, solution pH, co-existing ion effects, adsorption temperature, initial dye concentration) on the adsorption process were investigated. Experiments to investigate the mechanism of the CV-nanoclay adsorption system showed that the adsorption kinetics and equilibrium parameters fit better with the Pseudo second-order kinetic model and the Langmuir isotherm model, respectively. The maximum adsorption capacities (qm) of B1 and B2 adsorbents were obtained as 224.63 mg/g at 25°C and 360.30 mg/g at 45°C, respectively. A suitable combination of surface and CV ion charge was obtained at low pH values (=7) of the CV solution. The presence of co-existing NaCl ions did not significantly affect the CV adsorption capacity. When the results were evaluated, it was seen that the montmorillonite-based adsorbents were effective and cost-effective adsorbents for CV dye removal. [ABSTRACT FROM AUTHOR]

The toxicity of antibiotic residues in water resources adversely affects the environment. Recent studies have focused on the removal of organic pollutants such as antibiotics from aqueous solutions with cheap and environmentally compatible adsorbents. In this study, adsorption of oxytetracycline hydrochloride (OTCHCL) on the natural Manisa-Gördes clinoptilolite was investigated in the batch system at 298-323 K. Effects of pH, initial concentration, adsorbent dosage, contact time, stirring speed and temperature on adsorption were examined and optimum parameters were determined. Isotherm models including Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin were applied to analyze the adsorption data. Kinetic constants were determined by pseudo-first order (PFO), pseudo-second order (PSO), intraparticle diffusion and Elovich models. Adsorption of OTC-HCL on natural zeolite fitted well to the Freundlich and pseudo-second order models. The maximum adsorption capacity of natural zeolite was determined as 60.97 mg/g at 323 K. Thermodynamic studies indicated that the adsorption of OTC-HCL on natural zeolite was spontaneous and endothermic. Physicochemical characterization of natural zeolite was conducted by N2 adsorptiondesorption, XRD, FTIR, SEM-EDX analyses before and after adsorption. SBET, specific surface area of the natural zeolite decreased after adsorption process. Characterization results showed that OTC-HCL molecules were successfully adsorbed on the natural zeolite surface. [ABSTRACT FROM AUTHOR]

In the study, the removal performance of arsenic and antimony by drinking water treatment sludge (DWTS) was investigated. DWTS-200 was produced by thermal modification of the DWTS at three different temperatures (200, 400 and 600℃). The maximum arsenic removal was obtained at 200℃ and 1 hour contact time. The surface area and pore volume of adsorbent were analyzed by BET method; phase compositions were determined by X-ray diffraction (XRD), surface morphologies and elemental analyses were performed by scanning electron microscope (SEM) and energy disperse X-ray spectroscopy (EDS). The results showed that adsorbent had a relatively high surface area (170 m2 g-1) and was predominantly amorphous. The predominant phases were iron, calcite, oxygen, and quartz. The breakthrough volumes were obtained as 6,000 L (133,000 BV) and 640 L (14,000 BV) for 40 μg As L-1 and 80 μg Sb L-1 inlet concentrations. In order to determine the kinetic parameters and predict the breakthrough curves for column design, Thomas and Yoon-nelson models were applied. The column experimental data were fitted well to each model. The maximum adsorption capacity was calculated by Thomas model as 6.53 mg Asg-1, 5.21 mg Sbg-1. Regeneration studies were also shown that DWTS-200 could be reused after regeneration. [ABSTRACT FROM AUTHOR]

Activated carbons are widely used especially in the removal of harmful contents of gases and liquids. Activated carbons constitute one of the important import items for our country. It is foreseen that the production of activated carbons from cheap, easily available and abundant raw materials of various organic origins will make significant contributions to the country's economy. In this study, it is aimed to evaluate semi-bituminous coals (Gediz-Kütahya) containing high sulfur as an alternative area of use in the production of activated carbon. In the study where ZnCl2 was used as the activation chemical, the effects of different working parameters (chemical/coal ratio, impregnation time and grain size) on activated carbon production were investigated. Various properties such as BET surface area, pore distribution, SEM surface properties, adsorption capability etc. of the obtained activated carbon were determined. Comparisons of the obtained activated carbon with the imported activated carbons still used commercially were made, and it was determined that there were significant similarities in properties. Optimum production operating parameters, 1/1 ZnCl2/coal mixture ratio, 24 hours impregnation time and +2 mm particle size coal is treated at 650 oC for 60 minutes under N2 atmosphere, with 733 m2/g BET surface area, micro and meso porosity activated carbon with a total pore volume of 0.460 cm3/g was obtained. As a result of the adsorption tests of the obtained activated carbon, it was determined that 99.2% of the Cu2+ ions in the solution could be removed. It has been understood that the obtained activated carbon can be used in many sectors. [ABSTRACT FROM AUTHOR]

In this study, hydroxyapatites (FSHAp and ESHAp) from natural waste materials (fish bones and egg shells) were successfully synthesized and their physicochemical properties were characterized. Cu(II) ion adsorption potentials of FSHAp and ESHAp particles under different experimental conditions (pH, different adsorbent and Cu(II) concentration, contact time and temperature) were optimized by using the Response Surface Methodology (RSM), and their Cu(II) adsorption capacities were compared. The surface morphology, crystal structure, elemental contents, surface area and pore ratios of produced hydroxyapatitebased adsorbents were determined by using FTIR, SEM-EDX, XRD characterization techniques. Isotherm and kinetic models were calculated to determine their adsorption mechanism, and the results showed that the Cu(II) adsorption process of FSHAp and ESHAp particles was more suitable for the Tempkin and Scarthard isotherm models and the pseudo-second order kinetic model. The optimum adsorption capacity for Cu(II) removal for FSHAp and ESHAp particles were obtained as 19.4 mg/g and 10.6 mg/g, respectively (pH 5.5, 90 mg Cu(II)/L, 2g/L adsorbent concentration, 25℃ and 25 min). Desorption and regeneration studies have shown that adsorbents can be used effectively for up to three consecutive cycles. The results of this study revealed that FSHAp and ESHAp particles can be used as alternative, environmentally friendly, low-cost adsorbents for Cu(II) removal from aqueous environments and environmental improvements in the perspective of zero waste approach. [ABSTRACT FROM AUTHOR]

Pollution caused by synthetic dyes in wastewater has become an important problem. Especially the removal of MB used in dyeing cellulosic materials from waste water is an important issue. In this study, PANI/WS composites were presented as inexpensive and useful adsorbent materials. The composites were prepared at various mixing ratios. Chemical structures of the adsorbents were investigated by FTIR and surface morphologies were studied by SEM. The efficacies of pH, adsorbent amount, inceptive dyestuff concentration, time and temperature on MM adsorption capability of composites were examined. Kinetic and isotherm studies were executed at various temperatures. The adsorption behaviour was studied with the help of three main isotherm models. It was seen that the obtained data of isotherms matched more with the Langmuir and Temkin isotherms, respectively. The adsorption capacity of composite adsorbent was experimentally found to be 105 mg/g. The highest adsorption efficiency value was found to be 98.93%. The reaction kinetics were confirmed to match with the pseudo second order kinetic model. [ABSTRACT FROM AUTHOR]

Zonguldak is a major center of coal mines situated on the western BlackSea coast which has largest reserves of hard coal of Turkey, possesing many coal mines in the territory. In this study the investigation of acetone adsorption characteristics of activated carbons at room temperature obtained from Zonguldak-Karadon coal by physical and chemical methods is aimed. The effects of the adsorbent preparation technique, type of activation agent (KOH, NaOH, ZnCl2 ve H3PO4) and activation temperature (400-800?) on acetone adsorption were investigated. Acetone adsorption equilibrium data were compared with different adsorption isotherm models such as, the Brunauer-Emmett-Teller, Langmuir, Freundlich, Harkins-Jura, Dubinin-Radushkevich, Dubinin-Astakhov, Henderson, Halsey and Smith, in order to investigate the acetone adsorption mechanism on various activated carbons obtained from Karadon coal, and the model parameters were determined. The Langmuir model adsorption constant Wm that gives the maximum adsorption capacity was found with the values in the range 0,12-0,63 g/g. Adsorpsiyon characteristic energies E0 evaluated from the Dubinin-Radushkevich model were found in the range 2,87-29,80 kJ/mol. The activated carbons obtained by chemical treatment were found to have higher acetone adsorption capacities than the physically activated ones, and that the adsorption capacity increased proportionally with the total pore volume. The activated carbons obtained by KOH activation of Zonguldak-Karadon coal at 700 ve 800? were found to have the highest acetone adsorption capacities as 45% and 45,99%, respectively. The results of the study have shown that the activated carbons obtained by chemical activation were highly efficient for acetone adsorption and have high commercial potential for use in the removal of acetone vapors. [ABSTRACT FROM AUTHOR]

In this study, hydroxyapatite material was prepared for the removal of Remazol N.Blue RGB (RB203) from waters. In the synthesis of hydroxyapatite material, waste hen's eggshell was evaluated as calcium source. Synthesis of hydroxyapatites was performed at three different pH values (pH 9, 10 and 11) using precipitation method. Before and after calcination of eggshells, XRF, XRD and SEM analysis were carried out. Synthesized hydroxyapatites were characterized by TGA-DTA, XRD and FTIR analysis. At the end of the characterization studies, hydroxyapatite structure was obtained better in pH 10 medium, and adsorption studies were carried out with the material prepared at this pH value. The effects of pH (2-12), amount of sorbent (2-10 g/L) and concentration of dye (25-200 mg/L) on adsorption of RB203 using hydroxyapatite were examined. In order to determine the mechanism of adsorption, the Langmuir, Freundlich, Temkin and Henry isoterm equations were used. Comparing the adsorption isotherms in terms of correlation coefficients (R2), it was seen that the Langmuir, Freundlich and Temkin isotherm models were in good agreement with the experimental data. The highest adsorption capacity obtained with the Langmuir isotherm model was 27.93 mg/g. In order to examine the adsorption kinetics, the pseudo-first and the second order kinetic equations were used. The results of adsorption kinetics show that the adsorption of RB203 with hydroxyapatite was better expressed by the pseudo-second order kinetic equation. This study shows that the hydroxyapatite synthesized from waste calcined eggshell is a promising sorbent for adsorption of dye. [ABSTRACT FROM AUTHOR]

This study investigated removal efficiency of nickel in adsorption system by using the process waste obtained from the exit point of ore processing, modified with ultrasound and acid in laboratory. The experimental study was conducted in an intermittent process by taking into account the criteria of different adsorbent dosages (0,1-5 g/100 mL), pH (2-10), contact times (0-150 minutes) and mixing speeds (100-400 rpm). During experimental optimization, 100 mg/L initial nickel solution concentration, pH original (5.8), adsorbent dose 8 g/L, contact time 40 minutes, mixing speed 200 rpm, temperature 298 Kelvin (250C) was determined. Chemical properties and SEM images pertaining to modified process waste (MPA) were specified. In nickel removal, it was observed that the obtained results were found more concordant with Langmuir Isotherm models as evidenced by correlation coefficients. Kinetics data were obtained from treatment results, and qmax value obtained for MPA was found as 25.77 mg/g. [ABSTRACT FROM AUTHOR]

The removal of Ni(II) and Cr(VI) ions from aqueous solutions using chemically modified apricot kernel shells (P. armeniaca L.) was investigated in this research. Chemical modification methods effects on the adsorption capacity improvement for removal of heavy metals have been investigated. Structures of apricot kernel shells materials before and after modifications was examined by the FTIR and SEM analyses. HCl, NaOH and Fenton reactives were used for the modification processes. The investigation of kinetic, isotherm and thermodynamic parameters were also studied for HCl, NaOH and Fenton modified apricot kernel shells The rejeneration processes were studied for the determination of apricot kernel shells' reusability after the adsorption processes. Additional costs for applied modification processes were calculated and they were compared with the classical methods. The chemical oxygen demand (COD) residues in treated water by raw apricot kernel shells materials decreased from 910-1430 mg/L to 10-90 mg/L with the modification processes. The removal efficiencies changed with heavy metal concentration in water sample and increased up to 92% for apricot kernel shells materials. The adsorption capacities were found between 1 mg/g and 90 mg/g according to type of adsorbent and modification methods. As a result, it was revealed that adsorption capacities and costs of apricot kernel shells were compatible with conventional adsorbents. [ABSTRACT FROM AUTHOR]

By development of industrial activities, there has been an increase of heavy metal pollution in surface waters. During biological purify cation processes, the heavy metals have high toxic effects, especially on the microorganisms. Apparently, the heavy metals accumulating within plants watered using agriculture waters, and within the aquatic living things cause an accumulation in human beings. Because of this reason, the treatment of heavy metals from wastewaters that will be used in biological treatment as well as the purifications of water releasing to the environment gains importance. In this study, the removal of cadmium pollution using packed adsorption columns has been investigated. Oak valonia and horse chestnut have been used as adsorbents. At the result of the study, adsorption capacities of oak valonia and horse chestnut were determined as 26.32 and 14.59 mg cadmium /g adsorbent respectively. Also, there is maximum adsorption capacity in pedincula of oak valonia and this value is 40.24 mg cadmium/g adsorbent. [ABSTRACT FROM AUTHOR]