• Advances in environmental research
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• 제6권2호
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• pp.95-111
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• 2017

The valorization of swine manure samples, i.e., de-watered cake (SMc) and solid digestate (SMd), in products with beneficial value, i.e., low cost activated carbons (ACs), is studied. For this purpose slow pyrolysis and steam activation at three different duration times are applied. Additionally, the obtained ACs are characterized and tested towards removal of Cr(VI) from aqueous solutions. It is revealed that BET surface area varies in the range of $236-267m^2/g$ for ACs prepared from SMc sample and in the range of $411-432m^2/g$ for ACs prepared from SMd sample. Despite the low determined surface area of prepared ACs, a high total Cr removal capacity is observed occurring through a "coupled adsorption-reduction" mechanism. Higher Cr(VI) removal capacity is demonstrated for ACs having higher surface area ($q_m$ is 140.9 mg/g according Langmuir modelling). Cr(VI) removal is found to be pH dependent with a maximum at pH 1. However at that pH significant amounts of Cr remain in the solution as Cr(III). At pH 2 lower amount of Cr(VI) is removed compensated by a higher removal of Cr(III) resulting in a higher amount of adsorbed $Cr_{tot}$. Therefore adsorption at pH 2 is found to be appropriate. The removal capacity of the studied ACs towards Cr(VI) is almost independent of activation time.

• 산업경영시스템학회지
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• 제38권1호
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• pp.21-29
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• 2015

A steady-state controllable M/G/1 queueing model operating under the {T:Min(T,N)} policy is considered where the {T:Min(T,N)} policy is defined as the next busy period will be initiated either after T time units elapsed from the end of the previous busy period if at least one customer arrives at the system during that time period, or after T time units elapsed without a customer' arrival, the time instant when Nth customer arrives at the system or T time units elapsed with at least one customer arrives at the system whichever comes first. After deriving the necessary system characteristics including the expected number of customers in the system, the expected length of busy period and so on, the total expected cost function per unit time for the system operation is constructed to determine the optimal operating policy. To do so, the cost elements associated with such system characteristics including the customers' waiting cost in the system and the server's removal and activating cost are defined. Then, procedures to determine the optimal values of the decision variables included in the operating policy are provided based on minimizing the total expected cost function per unit time to operate the queueing system under considerations.

• 한국세라믹학회지
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• 제47권6호
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• pp.524-528
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• 2010

In this study, the structure and properties of waste oyster shell and its phosphorus removal efficiency were investigated. Waste oyster shells are troublesome environmental waste in the coastal region where the oysters are produced. Waste oyster shells were pyrolyzed by bench-scale rotary kiln for its activation. It shows maximum 76% of phosphorus removal efficiency for the municipal wastewater and livestock wastewater. We found that the activated oyster shells can be used as a phosphorus removal agent with the consideration of high efficiency, easy processing, and cost effectiveness.

• Carbon letters
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• 제11권3호
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• pp.224-234
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• 2010

Four activated carbons were produced by two-stage process as followings; semi-carbonization of indigenous biomass waste, i.e. cotton stalks, followed by chemical activation with KOH under various activation temperatures and chemical ratios of KOH to semi-carbonized cotton stalks (CCS). The surface area, total pore volume and average pore diameter were evaluated by $N_2$-adsorption at 77 K. The surface morphology and oxygen functional groups were determined by SEM and FTIR, respectively. Batch equilibrium and kinetic studies were carried out by using a basic dye, methylene blue as a probe molecule to evaluate the adsorption capacity and mechanism over the produced carbons. The obtained activated carbon (CCS-1K800) exhibited highly microporous structure with high surface area of 950 $m^2/g$, total pore volume of 0.423 $cm^3/g$ and average pore diameter of 17.8 ${\AA}$. The isotherm data fitted well to the Langmuir isotherm with monolayer adsorption capacity of 222 mg/g for CCS-1K800. The kinetic data obtained at different concentrations were analyzed using a pseudo-first-order, pseudo-second-order and intraparticle diffusion equations. The pseudo-second-order model fitted better for kinetic removal of MB dye. The results indicate that such laboratory carbons could be employed as low cost alternative to commercial carbons in wastewater treatment.

• Carbon letters
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• 제18권
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• pp.49-55
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• 2016

Refuse-derived fuel (RDF) produced using municipal solid waste was pyrolyzed to produce RDF char. For the first time, the RDF char was used to remove aqueous copper, a representative heavy metal water pollutant. Activation of the RDF char using steam and KOH treatments was performed to change the specific surface area, pore volume, and the metal cation quantity of the char. N₂ sorption, Inductively Coupled Plasma-Atomic Emission Spectrometer (ICP-AES), and Fourier transform infrared spectroscopy were used to characterize the char. The optimum pH for copper removal was shown to be 5.5, and the steam-treated char displayed the best copper removal capability. Ion exchange between copper ions and alkali/alkaline metal cations was the most important mechanism of copper removal by RDF char, followed by adsorption on functional groups existing on the char surface. The copper adsorption behavior was represented well by a pseudo-second-order kinetics model and the Langmuir isotherm. The maximum copper removal capacity was determined to be 38.17 mg/g, which is larger than those of other low-cost char adsorbents reported previously.

• Advances in environmental research
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• 제7권1호
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• pp.53-71
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• 2018

Waste glass disposal causes environmental problems in the cities. To find a suitable green environmental solution for this problem low cost adsorbent in this study was prepared from waste glass. An effective new green adsorbent was synthesized by hydrothermal treatment of waste glass (WG), followed by acidic activation of its surface by HCl (WGP). The prepared adsorbent was characterized by scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), and BET surface measurement. The developed adsorbent was used for the removal of heavy metals (Cd, Cu, Fe, Pb and Zn) from well water. Batch experiments were conducted to test the ability of the prepared adsorbent for the removal of Cd, Cu, Fe, Pb and Zn from well water. The experiments of the heavy metals adsorption by adsorbent (WGP) were performed at different metal ion concentrations, solution pH, adsorbent dosage and contact time. The Langmuir and Freundlich adsorption isotherms and kinetic models were used to verify the adsorption performance. The results indicated high removal efficiencies (99-100%) for all the studied heavy metals at pH 7 at constant contact time of 2 h. The data obtained from adsorption isotherms of metal ions at different time fitted well to linear form of the Langmuir sorption equation, and pseudo-second-order kinetic model. Application of the resulted conditions on well water demonstrated that the modified waste glass adsorbent successfully adsorbed heavy metals (Cd, Cu, Fe, Pb and Zn) from well water.

• Membrane and Water Treatment
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• 제14권3호
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• pp.121-128
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• 2023

This study introduces a NaOH/Zn-assisted hydrothermal method for the synthesis of zeolites derived from coal ash (CA). A zeolite/Zn adsorbent is successfully prepared by the activation of CA with NaOH and Zn; it is characterized by a high surface area and a negative surface charge.Methylene blue (MB) and methyl orange (MO) are selected as dye pollutants, and their adsorption onto the zeolite/Zn adsorbent is investigated. Results show the high adsorption capacities of MB and MO and that the negative surface charge facilitates electrostatic interactions between the adsorbates and adsorbents. The zeolite/Zn adsorbents shows the selective adsorption of positively charged dye MB via electrostatic interactions between the =NH+ group (positive dipole) and the oxygen functional group of the adsorbents (negative dipole). The selectivity for the positively charged dye is sufficiently high, with the removal efficiency reaching 99.41% within 10 min. By contrast, the negatively charged dye MO exhibits negligible absorption. These findings confirm the role of electrostatic interactions in the adsorption of MB, in addition to the effect of a large surface area. The results of this study are expected to facilitate the development of simple, eco-friendly, and cost-effective zeolite-based adsorptive composites from CA residuals for the selective removal of dye pollutants from CA waste.

• Bulletin of the Korean Chemical Society
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• 제33권10호
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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.

• Environmental Engineering Research
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• 제20권1호
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• pp.33-39
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• 2015

Mercury is a toxic pollutants present in different types of industrial effluents and is responsible for environmental pollution. Removal of Hg(II) ions from synthetic wastewater was studied using the activated biocarbon produced from the leaves of Tridax procumbens (Asteraceae). The particle size of the biocarbon (BC) is in the range of $100-120{\mu}m$. The effects of initial metal ion concentration, pH, contact time, and amount of biocarbon on the biosorption process were studied at temperature of $28{\pm}2^{\circ}C$. Batch experimental studies showed that an equilibrium time of 160 min was required for the maximum removal of Hg(II) at the optimized biocarbon dose of 2.5 g per 100 mL of synthetic wastewater. The optimum pH required for maximum removal (96.5%) of Hg(II) ions was found to be 5.5. The biosorption of metal ions onto activated biocarbon surface is probably via an ion exchange mechanism. The biocarbon can be regenerated with minimum loss. Further, it can be reused without any chemical activation. The findings of the research suggested that, the biocarbon produced from cost effective renewable resources can be utilized for the treatment of industrial wastewater.

• 한국세라믹학회지
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• 제38권10호
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• pp.928-935
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• 2001

본 연구에서는 PAN계 안정화섬유를 원료로 하여 수증기를 이용한 물리적 활성화에 의해 여러 등급의 활성탄소섬유를 제조하고, 비표면적, 요오드 흡착량, 미세구조, 세공구조 등을 측정하여 제조조건에 따른 그 특성변화를 고찰하였다. 수증기를 이용한 물리적 활성화에서 기존의 탄화과정과 활성화과정의 2단계를 이용한 공정과, 탄화공정과 활성화 공정을 동시에 수행하는 1단계 활성화과정을 비교함으로써 저가로 활성탄소섬유를 제조할 수 있는 제조방법을 연구하였다. 2단계 법에서는 안정화 섬유를 $900^{\circ}C$에서 탄화한 후 이를 다시 $900^{\circ}C$에서 활성화하는 방법으로 $1019m^2/g$의 비표면적을 갖는 활성탄소섬유를 얻었으나 1단계 방법에서는 $900^{\circ}C$에서 $1636m^2/g$의 비표면적을 갖는 활성탄소섬유를 제조하였다. 이들 활성탄소섬유 사이에는 비표면적, 요오드 흡착력, 기공분포 등이 서로 차이가 있음에도 불구하고, Brunauer-Deming-Deming-Teller(BDDT)에 의한 분류에서는 제I형을 나타내는 공통점도 가지고 있었다.