Evaluation of Kinetic Adsorption Models in Aquatic Environment, Models of Lagergren and Ho et al.
Ho Zahra AskariShayan ShamohammadiAli Hasantabar-AmiriKaveh Ostad‐Ali‐AskariSaeid EslamianVijay P. SinghZahra Askari
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Heavy metal pollution has become one of the most cucial environmental obstacle today.The treatment of heavy metals is of special concern due to their refractoriness and resistence in the environment.In recent years, different procedures for heavy metal removal from wastewater have been widely studied.This paper revises the common procedures that have been applied to treat heavy metal wastewater and considers these techniques.Presently kinetic adsorption equations are widely used in adsorption processes.The main objective of the present research is to evaluate the linear and non-linear equations of the Lagergren and Ho et al. models in the kinetics of nickel adsorption by activated carbon.For this purpose, powdered activated carbon, the raw material of which is wood, was purchased from the "Merck" company (Germany).The optimum PH of the adsorption was obtained to be 6.As well, the kinetics of adsorption showed that for the initial nickel concentration of 2.5, 5, 10, 50 and 125 mg/L, equilibrium time was 40, 75, 120, 150, 50 minutes respectively.The maximum removal efficiency of nickel in the initial concentration of 2.5 mg/L was obtained to be 89.6%.The fitting of the four linear kinetic models of Ho et al. (1995), and its non-linear model, as well as the linear model ofkinetic data of adsorption at different concentrations showed that the non-linear model of Ho et al. (1995) better describes the kinetic data of nickel adsorption by activated carbon thanhis linear models.Comparison of the non-linear models of Ho et al. and Lagergren (1893) showed that in low concentrations the non-linear model of Ho et al., and in high concentrations non-linear model of Lagergren better describes the kinetic data of adsorption.First and second-order rate equations were pragmatic to etude adsorption kinetics.The most significant advantage of the offered model is its capability to predicate the balance time of adsorption, which is very essential to optimize the expense of the adsorption system design.The received consequences depict that the new model can analyze the experiential information very well.The equation is received clearly by changing the mass balance equation of a single step batch-type system into integrated first order rate equation.The proposed new formulation depends on maximum sorption (or removal) rather than equilibrium sorption, as given by Lagergren equation.The precise value of equilibrium sorption is not easy to describe in many cases, and it is exhibit that the modified formulation prepares better correlation with sorption data when the procedure is far from completion.A corrected formulation of the popular Lagergren pseudo first order rate equation is proposed.The equation is created clearly by changing the mass balance equation of a single step batch-type system into unified first order rate equation.The proposed new formulation depends on maximum sorption (or removal) rather than equilibrium sorption, as given by Lagergren equation.The precise value of equilibrium sorption is not simple to describe in many cases, and it is exhibited that the modified formulation provides better correlation with sorption data when the process is far from completion.Past disposal of volatile organic solvents has resulted in contamination of soils at U.S. Army installations. Technologies that involve volatilizing or air stripping contaminants from contaminated soils are used for remediation of these sites. The resulting stream of gaseous volatile organic compounds (VOCs) must be treated before the air stream is released to the atmosphere. Thermal treatment or carbon adsorption of gaseous VOCs is effective but expensive. The present study was conducted to evaluate the utility of using fixed populations of VOC-degrading microorganisms to destroy (mineralize to inorganic products) gaseous VOCs. This technology holds potential as a cost effective alternative or supplement to thermal treatment or carbon adsorption. The VOCs investigated include benzene, carbon tetrachloride, chlorobenzene, methyl ethyl ketone (MEK), toluene, and trichloroethylene (TCE).
Volatile organic compound
Chlorobenzene
Air stripping
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Abstract Arsenic (As) contamination in drinking water is a serious problem in a number of countries in the world, especially in small communities and developing countries. Arsenic is related to many health diseases. Several technologies such as coagulation, adsorption, ion exchange and membrane processes, etc., are used in removing arsenic from water. In this study, a new material, namely iron-coated sponge (IOCSp), was developed and used to remove As, and it was found that IOCSp has a high capacity for removing both As(V) and As(III). Each gram of IOCSp adsorbed about 160 µg of As upon a 9-h contact of IOCSp with As solution. A dynamic filter column conducted showed that even a small quantity of IOCSp (8 g) could reduce As from 156 µg/L to a concentration of less than 50 µg/L while treating 75 L of groundwater contaminated with arsenic. Both the filtration rate and the size of the sponge had an effect on effluent quality, and the amount of water treated to the acceptable quality.
Filtration (mathematics)
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Among the different organic pollutants commonly present in contaminated ground and surface waters, wastewaters, and hazardous landfill leachates, polychlorinated biphenyls (PCBs) have attracted much concern due to their wide distribution, high persistence in the environment, and possible adverse health effects. Although activated carbon adsorption has been demonstrated to be effective in removing PCBs from drinking water, little work has been done to evaluate their removal from leachate matrices. The present investigation therefore focused on the adsorption of PCBs from a hazardous landfill leachate. The leachate was characterized, and found to contain several organics such as phenol and dichlorobenzenes (COD = 10,000 mg/L). In order to examine the effect of background substances on adsorption, equilibrium studies were conducted with {sup 14}C radiolabeled PCBs using different background solutions including, organic free water (OFW), leachate matrix, and phenol. Furthermore, equilibrium studies were performed with leachate sediments, predominantly consisting of ferric hydroxide, to evaluate their capacity for PCBs.
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During land treatment of wastewater, significant amounts of heavy metals may be introduced into the soil system. Chemical forms of the deposited metal elements would affect their reactivities and pollution potential in the environment. Attempts were made to fractionate heavy metals in the soil using three established chemical extraction procedures. Based on metal recovery efficiencies, a sequential extraction procedure was adopted to partition heavy metals in the soils of a long-term cropland wastewater disposal site near Santiago, Chile. Results indicated consistently higher metal recovery percentages in the wastewater-affected soils. Although considerable amounts of heavy metals in the wastewater were chemically soluble, exchangeable and adsorbed, most of the accumulated metals were present in the soil in organic form (such as Cu) or as inorganic precipitates (such as Zn). The lack of soluble and exchangeable metals in the soil significantly reduces the downward leaching potential of deposited metals. However, the labile nature of the accumulated metal elements would enrich the soil with plant-available heavy metal elements for a long time to come.
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Predictability
Carbon fibers
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Ecotoxicity
Degradation
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국내에서 광범위하게 사용되고 있는 살충제 imidacloprid의 토양흡착 특성과 벼 재배 환경중 용탈 가능성을 평가하기 위하여 방사성 동위원소로 표지된 $[^{14}C]$ limidacloprid를 이용하여 수원근교 논토양 2종을 대상으로 시험하였다. Freundlich 흡착 등온식으로부터 구한 imidacloprid의 흡착상슈$(K_f)$ 는 $1.7{\sim}2.6$ , 기울기(1/n)는 1 미만, 토양 유기탄소기준흡착계수$(K_{oc})$ 는 $228{\sim}249$ , 토양 반감기를 이용한 지하수 오염가능성(GUS index)은 $1.6{\sim}2.4$ 로 흡착성이 중간 정도로 평가되어 토양중 용탈 가능성은 높지 않았다. 논토양에서 용탈성은 숙성잔류물 함유 토양보다 신생잔류물 함유 토양에서 더 높았다. 논토양의 토층별 $^{14}C$ 의 분포는 $0{\sim}10cm$ 깊이에 80% 이상이 분포하였으며, 벼 재배구에서 처리된 $^{14}C$ 의 식물체로의 이동성은 신생잔류물 함유 토양이 숙성잔류물 함유 토양보다 높았으나 식물체로 흡수된 $^{14}C$ 은 총처리량의 약 3% 미만으로서 imidacloprid의 용탈성과 생물이용도가 매우 낮음을 시사하였다. In order to elucidate the adsorption and leaching characteristics of the insecticide imidacloprid in two types of paddy soils near Suwon, this experiment was carried out with $[^{14}C]$ imidacloprid as a radiotracer. In an adsorption study conducted using $[^{14}C]$ imidacloprid in 2 test soils, the adsorption coefficient was higher in soil A $(K_f\;2.6)$ than that in soil B $(K_f\;1.7)$ . As calculated from Freundlich constant, distribution coefficients and half lives in soils, GUS indices showed low leachabilities of imidacloprid treated on the paddy soils into the groundwater. The amount of imidacloprid leached from the soil columns during the 4 weeks of leaching was less than 2% of the originally treated $^{14}C$ . In the leaching test the amounts of $^{14}C$ activities distributed in the soil layer of 0-10 cm were more than 80% of the originally tented $^{14}C$ and those in rice plants were less than 3% of the originally treated $^{14}C$ , suggesting that imidacloprid has very low teachability and bioavailability.
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