• Carbon letters
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• v.10 no.4
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• pp.293-299
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• 2009

Potassium hydroxide activated carbons were prepared from Egyptian petroleum cokes with different KOH/coke ratios and at different activation temperatures and times. The textural properties were determined by adsorption of nitrogen at $-196^{\circ}C$. The adsorption of iodine and methylene blue was also investigated at $30^{\circ}C$. The surface area and the non-micropore volume increased whereas the micropore volume decreased with the increase of the ratio KOH/coke. Also the surface area and porosity increased with the rise of activation temperature from 500 to $800^{\circ}C$. Textural parameter considerably increased with the increase of activation time from 1 to 3 h. Further increasing of activation time from 3 to 4 h was associated with a less pronounced increase in textural parameters. The adsorption of iodine shows the same trend of surface area and porosity change exhibited by nitrogen adsorption, with KOH/coke ratio and temperature of activation. Adsorption of methylene blue follows pseudo-first-order kinetics and its equilibrium adsorption follows Langmuir and D-R models.

• Journal of Forest and Environmental Science
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• v.32 no.3
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• pp.253-261
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• 2016

Xanthoceras sorbifolia seed coat (XSSC) is a processing residue of the bioenergy crop. This work aimed to evaluate the applicability of using the steam explosion to modify the residue for dye biosorption from aqueous solutions by using methylene blue as a model cationic dye. Equilibrium, kinetic and thermodynamic parameters for the biosorption of methylene blue on the steam-exploded XSSC (SE-XSSC) were evaluated. The kinetic data followed the pseudo-second-order model, and the rate-limiting step was the chemical adsorption. Intraparticle diffusion was one of the rate-controlling factors. The equilibrium data agreed well with the Langmuir isotherm, and the biosorption was favorable. The steam-explosion pretreatment strongly affected the biosorption in some respects. It reduced the adsorption rate constant and the initial sorption rate of the pseudo-second-order model. It enhanced the adsorption capacity of methylene blue at higher temperatures while reduced the capacity at lower ones. It changed the biosorption from an exothermic process driven by both the enthalpy and the entropy to an endothermic one driven by entropy only. It increased the surface area and decreased the pH point of zero charge of the biomass. Compared with the native XSSC, SE-XSSC is preferable to MB biosorption from warmer dye effluents.

• Journal of the Korean Chemical Society
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• v.16 no.4
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• pp.241-248
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• 1972

The adsorption of Methylene Blue on Yeong-Il bentonite which was treated by aqueous NaOH, $Na_2SO_4 or NaHSO_4 solution respectively, varying concentrations, temperature and time, was studied. In case of treatment with NaHSO_4 solution, slight improvement of the adsorption of Methylene Blue on bentonite was observed. With Na_2SO_4$ solution, the best results obtained when bentonite was treated with 1 N of the solution for 2hr at $100^{\circ}C$, and the adsorption capacity of the product was 3 times better than that of original bentonite. At the higher concentration and the higher temperature than above, faujasite was formed. With NaOH solution, the best condition was in 1N solution for 1hr at $100^{\circ}C$ and the adsorption capacity of the product was 3.3 times better than that of original bentonite. At the higher concentration of the treating agent and at the higher temperature than above, hydroxysodalite was formed.

• Carbon letters
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• v.14 no.1
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• pp.27-33
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• 2013

An increase in population initiating rapid industrialization was found to consequently increase the effluents and domestic wastewater into the aquatic ecosystem. In this research the potentialities of Sambucus nigra L. (SNL) plant in the remediation of water, contaminated with methylene blue (MB), a basic dye were investigated. SNL was chemically impregnated with $KHCO_3$. Operating variables studied were pH, amount of adsorbent and contact time. In general, pH did not have any significant effect on colour removal and the highest adsorption capacity was obtained in 0.035 g MB/g-activated carbon. The Langmuir, Freundlich, Temkin and Dubinin-Radushkevich adsorption models were applied to describe the equilibrium isotherms. The adsorption isotherm data were fitted to the Temkin isotherm. The mass transfer property of the sorption process was studied using Lagergren pseudo-first-order and chemisorption pseudo-second-order kinetic models. The sorption process obeyed the pseudo-second-order kinetic model. The surface area, pores volume and diameter were assessed by the Brunauer-Emmett-Teller and Barrett-Joyner-Halenda methods. The results were compared to those from activated carbon (Merck) and an actual sample. The results indicate that SNL can be employed as a natural and eco-friendly adsorbent material for the removal of dye MB from aqueous solutions.

• Journal of the Optical Society of Korea
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• v.10 no.1
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• pp.28-32
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• 2006

We propose a new pH-sensing scheme using a methylene blue adsorption on an optical fiber cladding surface. Interactions between the silica and hydroxyl ions of a base solution induce the surface of the silica negatively charged. The charged surface attracts the positively charged chromophores of methylene blue. As the pH of the solution is reduced, the electrostatic attraction will also be reduced. This electrostatic attraction can change the transmitted light intensity of the cladding mode, since the boundary condition changes. We also carried out a simulation to verify the effect from external refractive index change around a long-period fiber grating. Our results confirm that the wavelength shift by external refractive index change is negligible compared to the transmitted light intensity variation of the cladding mode. By using a long-period grating pair, we can detect the cladding mode transmittance variations. Experimentally, we showed the possibility of pH sensing in the $1.5{\mu}m$ infrared region.

• Advances in environmental research
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• v.5 no.4
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• pp.225-235
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• 2016

Synthesized hydroxyapatite (Hyd) and Fe-hydroxyapatite (Fe-Hyd) composite were used for the removal of Methylene Blue (MB) from aqueous solutions in this study. The effect of adsorbent amount, pH and initial MB concentration were carried out to investigate in the aqueous solution. The kinetic study shows that the MB adsorption process with Hyd or Fe-Hyd follow pseudo-second order kinetic model. Experimental results are well fitted to the Langmuir isotherm model. The maximum adsorption capacities of Hyd and Fe-Hyd were obtained as 2.90 mg/g and 5.64 mg/g for MB according to Langmuir Isotherm models, respectively. Fe-Hyd composite increased the adsorption capacity of Hyd by 1.95 times that Hyd. It is concluded that Fe-Hyd composite is promising and economical adsorbent for MB removal in the aqueous solution.

• Journal of Korean Society on Water Environment
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• v.37 no.6
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• pp.483-492
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• 2021

This study evaluated the removal efficiencies of methylene blue (MB) and humic acids (HA) using a rice husk (RH) biochar and powdered activated carbon (PAC). The pseudo-second-order model better presented the adsorption of MB and HA onto a RH biochar than the pseudo-first-order model. Furthermore, better description of the adsorption behavior of MB and HA by the Langmuir isotherm model (R² of the RH biochar: MB = 0.986 and HA = 0.984; R² of PAC: MB = 0.997 and HA = 0.989) than the Freundlich isotherm model (R² of the RH biochar: MB = 0.955 and HA = 0.965; R² of PAC: MB = 0.982 and HA = 0.973) supports the assumption that monolayer adsorption played key roles in the removal of MB and HA using the RH biochar and PAC. Batch experiments were performed on the effects of dosage, temperature, and pH. For all experiments, PAC showed higher efficiencies than RH biochar and MB adsorption efficiencies were higher than those of HA. Adsorption efficiencies increased with increasing amounts of adsorbents and temperature. As the pH increased, adsorption efficiencies of MB were increased while adsorption efficiencies of HA were decreased.

• Bulletin of the Korean Chemical Society
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• v.33 no.10
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• pp.3184-3190
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• 2012

Color impurity in industrial effluents pose a significant risk to human health and the environment, so much effort has been expended to degrade them using various methods, including the use of clay minerals as adsorbent. The purpose of this study was to advance understanding of the mechanisms for the removal of methylene blue (MB) from aqueous solutions onto montmorillonite as an adsorbent. Preliminary experiments showed that montmorillonite was effective for this purpose and adsorption equilibrium could be reached in about 24 h. Adsorption capacity of the clay decreased with increase in temperature and ionic strength, and increased with in pH. The fitness of equilibrium data to common isotherm equations such as the Langmuir, Freundlich, Elovich, Temkin and Dubinin-Radushkevich were tested. The Langmuir equation fitted to equilibrium data better than all tested isotherm models. Thermodynamic activation parameters such as ${\Delta}G^0$, ${\Delta}S^0$ and ${\Delta}H^0$ were also calculated and results were evaluated. As result montmorillonite clay was found as effective low cost adsorbent for removal of cationic dyes from waste waters.

• Journal of Energy Engineering
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• v.13 no.2
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• pp.166-172
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• 2004

The activated carbon was produced from Sancheong bamboo by steam and carbon dioxide gas activation methods. The carbonization of raw material was conducted at 90$0^{\circ}C$ and gas activation reactions were conducted with respect to various conditions. -activation temperature 750-90$0^{\circ}C$, the flow rate of steam 0.5-2g-$H_2O$/g-char$.$hr, the flow rate of carbon dioxide 5-30$m\ell$-$CO_2$/g-char-min and activation time 1-5 hr. The prepared activated carbons were measured yield, the adsorption capacity of iodine and methylene blue, BET specific surface area and pore size distribution. The adsorption capacity of iodine (680.5-1526.1 mg/g) and methylene blue (18.3-221.5 mg/g) increased with creasing activation temperature and activation time. The adsorption capacity of iodine and methylene blue increased with the activation gas quantity in the range of 0.5-1.5g-$H_2O$/g-charㆍhr, 5-18.9$m\ell$-Co$_2$/g-charㆍmin. But those decreased over those range due to the pore shrinkage. The steam activation method was superior in efficiency to carbon dioxide activation method.

• Carbon letters
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• v.15 no.2
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• pp.105-112
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• 2014

Wastewater from textile industries is a major cause of water pollution in most developing countries. In order to address the issues of water pollution and high cost for treatment processes, the use of an inexpensive and environmentally benign adsorbents has been studied. The objective was to find a better alternative to the conventional methods. Lemon grass waste (ash) collected from a lemon grass stream distillation subunit in Bhutan was tested for dye removal from aqueous solutions. The study investigated the removal of methylene blue using the following operational parameters: initial concentration (100-600 mg/L), contact time, adsorbent dose (0.1-0.55 gm/100 mL), and pH (3-10). It was found that the percentage removal of dye increased with a decrease of the initial concentration and increased contact time and dose of adsorbent. The basic pH solution of dye showed better adsorption capacity as compared to the acidic dye solution. Langmuir and Freundlich adsorption isotherms were fitted to the data well. Data fitted better to Lagergren pseudo 2nd order kinetics than a 1st order kinetic model. Surface morphology was also examined via scanning electron microscopy. An elemental analysis was also carried out and the chemical composition and functional groups were analyzed using energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy techniques, respectively. The obtained results indicate that lemon grass ash could be employed as a low cost alternative to commercial activated carbon in wastewater treatment for the removal of dyes.