Chromium(VI) sorptive removal from aqueous solutions by nanocrystalline akaganèite

In this study, akaganeite (beta-FeO(OH)) an ironoxyhydroxide material, was used as a low-cost potential adsorbent for the removal of hexavalent chromium from aqueous solutions. The influence of agitation speed, solution pH, initial chromium concentration, sorbent concentration and temperature were evaluated at batch kinetic runs. It was shown that the solid diffusion model, in comparison to simple reaction kinetic models, described better the sorption kinetics. Freundlich and Frumkin isotherm best fitted the equilibrium results. Akaganeite presented a sorption capacity approximately 80 mg Cr(VI) g(-1), under the conditions studied. Flotation was used as a downstream process for the effective removal of the loaded material.     

Sorption of Zn(II) in aqueous solutions by scoria

We conducted kinetic and equilibrium sorption experiments on removal of Zn(II) from aqueous solutions by scoria (a vesicular pyroclastic rock with basaltic composition) from Jeju Island, Korea, in order to examine its potential use as an efficient sorbent. The batch-type kinetic sorption tests under variable conditions indicated that the percentage of Zn(II) removal by scoria increases with decreasing initial Zn(II) concentration, particle size, and sorbate/sorbent ratio. However, the sorption capacity decreases with the decrease of the initial Zn(II) concentration and sorbate/sorbent ratio. Equilibrium sorption tests show that Jeju scoria has a larger capacity and affinity for Zn(II) sorption than commercial powdered activated carbon (PAC); at initial Zn(II) concentrations of more than 10mM, the sorption capacity of Jeju scoria is about 1.5 times higher than that of PAC. The acquired sorption data are better fitted to the Langmuir isotherm than the Freundlich isotherm. Careful examination of ionic concentrations in sorption batches suggests that the sorption behavior is mainly controlled by cation exchange and typically displays characteristics of 'cation sorption'. The Zn(II) removal capacity decreases when solution pH decreases because of the competition with hydrogen ions for sorption sites, while the Zn(II) removal capacity increases under higher pH conditions, likely due to hydroxide precipitation. At an initial Zn(II) concentration of 5.0mM, the removal increases from 70% to 96% with the increase of initial pH from 3.0 to 7.0. We recommend Jeju scoria as an economic and efficient sorbent for Zn(II) in contaminated water.     

Removal of cationic dyes from aqueous solutions using microspherical particles of fly ash

Batch sorption experiments were carried out for the removal of cationic dyes (methylene blue and malachite green) from their aqueous solutions using sorbent made from fly ash-a waste material. Effects of various experimental parameters: initial dye concentration, contact time, pH, adsorbent dosage, solution temperature, surfactant addition and ionic strength on the fly ash sorption of dyes were evaluated. The isothermal data for sorption followed the Langmuir model. The maximum sorption capacity obtained for methylene blue and malachite green was 36.05 mg/g and 40.65 mg/g, respectively. Kinetic studies indicate that sorption on fly ash follows the pseudo-second order kinetics. Present research suggests that fly ash could be an appropriate adsorbent for the removal of basic dyes from aqueous solutions.     

Use of carbonised beet pulp carbon for removal of Remazol Turquoise Blue-G 133 from aqueous solution

Carbonised beet pulp (BPC) produced from agricultural solid waste by-product in sugar industry was used as adsorbent for the removal of Remazol Turquoise Blue-G 133 (RTB-G 133) dye in this study. The kinetics and equilibrium of sorption process were investigated with respect to pH, temperature and initial dye concentration. Adsorption studies with real textile wastewater were also performed. The results showed that adsorption was a strongly pH-dependent process, and optimum pH was determined as 1.0. The maximum dye adsorption capacity was obtained as 47.0 mg g^?1at the temperature of 25 °C at this pH value. The Freundlich and Langmuir adsorption models were used for describing the adsorption equilibrium data of the dye, and isotherm constants were evaluated depending on sorption temperature. Equilibrium data of RTB-G 133 sorption fitted very well to the Freundlich isotherm. Mass transfer and kinetic models were applied to the experimental data to examine the mechanisms of adsorption and potential rate-controlling steps. It was found that both external mass transfer and intra-particle diffusion played an important role in the adsorption mechanisms of dye and adsorption kinetics followed the pseudo second-order type kinetic model. The thermodynamic analysis indicated that the sorption process was exothermic and spontaneous in nature.     

Removal of aqueous nickel (II) using laterite as a low-cost adsorbent.

The present paper describes the laboratory study of laterite as a low-cost adsorbent for removal of aqueous nickel (II). At pH 7 and a temperature of 30 degrees C, a sorbent dose of 15 mg/L resulted in approximately 90% removal of nickel (II) from its initial concentration of 10 mg/L. A maximum removal of 98% of the adsorbate was observed with an adsorbent particle size of 210 micro with the above conditions. Batch kinetics results were described by fitting in a Langmuir isotherm. Helffrich's half-time equation (Helffrich, 1962) has been applied to evaluate the adsorption process. It appears that film diffusion would be the rate-limiting step. The effect of pH on the sorption process was carried out to a value of 8.0. The removal rate of nickel was found to be the function of pH of the reaction mixture. The rate of nickel uptake by laterite with the decrease in pH value has been explained on the basis of aqueous-complex formation and the subsequent acid-base dissociation at the solid-solution interface.     

Arsenic(III) removal by adsorption on sawdust carbon

Studies on the removal of As(III) by adsorption on sawdust and sawdust carbon have been carried out at room temperature (25 ± 1°C). The adsorption isotherm of As(III) on sawdust carbon was obtained in a batch reactor. The process of uptake follows the first-order adsorption rate expression and obeys the Langmuir and Freundlich model of adsorption. The mass transfer coefficients as a function of initial sorbate concentration have been determined. Parameters such as pH and absorbent dose were studied. Maximum adsorption capacity was observed at pH 7.0.     

Sorption media for stormwater treatment--a laboratory evaluation of five low-cost media for their ability to remove metals and phosphorus from artificial stormwater

Five sorption materials were studied with a focus on polishing pretreated stormwater: crushed limestone, shell-sand, zeolite, and two granulates of olivine. These materials are commercially available at comparatively low cost and have been subjected to a minimum of modification from their natural states. The sorbents were tested for phosphorus, arsenic, cadmium, chromium, copper, nickel, lead, and zinc at concentration and conditions relevant for typical stormwater. The materials were tested for sorption capacity and kinetics. Desorption was tested under neutral and alkaline conditions and in the presence of chloride. For most sorbent/sorbate combinations, significant sorption occurred within the first minutes of contact between sorbent and sorbate. Treatment to the low microgram per liter range could be achieved by contact times of less than 1 hour. The study indicated that sorption filters can be designed for long life expectancy at comparatively low cost by applying the materials tested.     

Predictive modeling of an azo metal complex dye sorption by pumpkin husk

Effective disposal of pumpkin husk (PH) as a redundant waste is a significant work for environmental protection and full utilization of resource. Predictive modeling of sorption of Lanaset Red (LR) G on PH was investigated in a batch system as functions of particle size, adsorbent dose, pH, temperature, and initial dye concentration. Fourier transform infrared spectroscopy attenuated total reflectance spectra of PH powders before and after the sorption of LR G were determined. Sorption process was found to be dependent on particle size, adsorbent dose, pH, temperature, initial dye concentration, and contact time. Amine and amide groups of PH had significant effect on the sorption process. The pH_zpc of PH was found as 6.4. Sorption process was very fast initially and reached equilibrium within 60 min. Dynamic behavior of sorption was well represented by logistic and Avrami models. The sorption of LR G on PH was excellently described by Langmuir model, indicating a homogeneous phenomenon. Monolayer sorption capacity decreased from 440.78 to 436.28 mg g^?1 with increasing temperature. Activation energy, thermodynamic, and desorption studies showed that this process was physical character, exothermic, and spontaneous. This study confirmed that PH as an effective and low-cost adsorbent had a great potential for the removal of LR G as an alternative eco-friendly process.     

Comparative study of chromium biosorption by red, green and brown seaweed biomass

Dried biomass of the macroalgae Fucus vesiculosus and Fucus spiralis (brown), Ulva spp. (comprising Ulva linza, Ulva compressa and Ulva intestinalis) and Ulva lactuca (green), Palmaria palmata and Polysiphonia lanosa (red) were studied in terms of their chromium biosorption performance. Metal sorption was highly pH dependent with maximum Cr(III) and Cr(VI) sorption occurring at pH 4.5 and pH 2, respectively. Extended equilibrium times were required for Cr(VI) binding over Cr(III) binding (180 and 120min, respectively) thus indicating possible disparities in binding mechanism between chromium oxidation states. The red seaweed P. palmata revealed the highest removal efficiency for both Cr(III) and Cr(VI) at low initial concentrations. However, at high initial metal concentrations F. vesiculosus had the greatest removal efficiency for Cr(III) and performed almost identically to P. lanosa in terms of Cr(VI) removal. The Langmuir Isotherm mathematically described chromium binding to the seaweeds where F. vesiculosus had the largest q(max) for Cr(III) sorption (1.21mmol g(-1)) and P. lanosa had the largest Cr(VI) uptake (0.88mmol g(-1)). P. palmata had the highest affinity for both Cr(III) and Cr(VI) binding with b values of 4.94mM(-1) and 8.64mM(-1), respectively. Fourier transform infrared analysis revealed interactions of amino, carboxyl, sulphonate and hydroxyl groups in chromium binding to Ulva spp. The remaining seaweeds showed involvement of these groups to varying degrees as well as ether group participation in the brown seaweeds and for Cr(VI) binding to the red seaweeds.     

Low cost sorbents for the removal of methyl parathion pesticide from aqueous solutions

Sorptive potential of selected agricultural waste materials i.e. rice (Oryza sativa) bran (RB), bagasse fly ash (BFA) of sugarcane (Saccharum officinarum), Moringa oleifera pods (MOP) and rice husk (RH) for the removal of methyl parathion pesticide (MP) from surface and ground waters has been investigated. Optimization of operating parameters of sorption process, i.e. sorbent dose, agitation time, pH, initial concentration of sorbate, and temperature have been studied. The sorption data fitted to Freundlich, Langmuir and Dubinin-Radushkevich (D-R) sorption isotherms. The maximum capacities of RB, BFA, MOP and RH for MP were calculated to be 3.6+/-0.8, 5.3+/-1.4, 5.2+/-1.5 and 4.7+/-1.0 mmolg(-1) by Freundlich, 0.39+/-0.009, 0.39+/-0.005, 0.36+/-0.004 and 0.35+/-0.008 mmolg(-1) by Langmuir and 0.9+/-0.08, 1.0+/-0.10, 1.0+/-0.10 and 0.9+/-0.07 mmolg(-1) by D-R isotherms respectively, employing 0.1g of each sorbent, at pH 6, 90 min agitation time and at 303 K. Application of first order Lagergren and Morris-Weber equations to the kinetic data yielded correlation coefficients, close to unity. Thermodynamic parameters of sorption process, i.e. DeltaH, DeltaS and DeltaG were computed and their negative values indicated the exothermic and spontaneous nature of sorption process. The pesticide may be stripped by sonication with methanol, making the regeneration and reutilization of sorbents promising. The sorbents investigated exhibited their potential applications in water decontamination, treatment of industrial and agricultural waste waters.     

Diffusion mechanism of lindane into wood charcoal

Abstract

The wood charcoal treated by 1N HNO₃ (WCT) was used to remove toxic chlorinated pesticide lindane (y‐HCH) residue from water by the sorption process. Using a simple first order reversible kinetics constants and half time equations, the film and pore diffusion coefficients were determined. Film diffusion was found to be rate limiting step in sorbing lindane by WCT. This was further authenticated by kinetics studies at different initial sorbate concentrations, different sorbent sizes, and different agitation speeds besides interruption test. A pore diffusion model was used to fit the data of kinetics in continuously mixed batch reactors (CMBR), and the tortuosity, external resistance, and surface diffusion effects on lindane sorption by WCT were noticed. The tortuosity values of 15 to 28 were obtained for WCT‐lindane system.     

生物磁分离新技术处理含铬废水最佳条件的研究

为了探索新工艺"趋磁细菌-磁分离法"处理含铬废水的最佳条件,首先进行了趋磁细菌对铬离子的去除影响因素试验,研究了pH、温度、时间和微生物量对吸附的影响;其次进行了趋磁细菌的分离试验,考查了磁分离器中悬丝摆放位置和磁场强度对溶液中菌体的去除效果的影响.试验结果表明,体系的pH值对铬离子的去除效率影响最大,pH值的最佳范围为5～11;在室温范围内,温度对吸附的影响不大;随着菌量的增加,菌对Cr(Ⅲ)的去除率略有提高,而单位质量菌的吸附量却有明显下降.在分离趋磁细菌时,磁场强度为100高斯时分离效果很高,而超过100高斯以后,效果不明显;另外,分离器中的金属丝和磁场方向垂直放置要比平行放置效果好,并用扫描电镜放大5 000倍观察了金属丝上被捕集的趋磁细菌的形态和结构.     

Heavy metals removal from wastewaters using organic solid waste—rice husk

In this study, the removal of Cr(III) and Cu(II) from contaminated wastewaters by rice husk, as an organic solid waste, was investigated. Experiments were performed to investigate the influence of wastewater initial concentration, pH of solution, and contact time on the efficiency of Cr(III) and Cu(II) removal. The results indicated that the maximum removal of Cr(III) and Cu(II) occurred at pH 5–6 by rice husk and removal rate increased by increased pH from 1 to 6. It could be concluded that the removal efficiency was enhanced by increasing wastewater initial concentration in the first percentage of adsorption and then decreased due to saturation of rice husk particles. Also according to achieved results, calculated saturation capacity in per gram rice husk for Cr(III) and Cu(II) were 30 and 22.5 mg?g^?1, respectively. The amounts of Cr(III) and Cu(II) adsorbed increased with increase in their contact time. The rate of reaction was fast. So that 15–20 min after the start of the reaction, between 50 and 60 % of metal ions were removed. Finally, contact time of 60 min as the optimum contact time was proposed.     

Sorption of 1-hydroxy-2-naphthoic acid to goethite, lepidocrocite and ferrihydrite: batch experiments and infrared study

The adsorption of naphthoic acids to iron oxides and hydroxides influences strongly their mobility in soils and sediments. Sorption of 1-hydroxy-2-naphthoic acid (HNA) to three iron oxides was examined over a wide range of conditions (pH, ionic strength, sorbate and sorbent concentrations). In the examination of HNA sorption, Tempkin model was performed to fit sorption data of HNA onto all iron oxides. The adsorption in the Henry law range increases in the order: goethite相似文献   

Sorption of pentachlorophenol on pine bark

The minimization of pentachlorophenol (PCP) transport in the environment driven by industrial wastewater discharges can be accomplished by sorption in natural, available and low cost by-products like pine bark. Taking into account that PCP is a chemical which behaviour is highly dominated by the surrounding features, this work intended to evaluate the sorption kinetics and equilibrium parameters according to the pH and temperature as well as the pine bark particle size. The PCP uptake by pine bark showed to be faster in the initial phase followed by a slower process, being 24 h the suitably time to reach the sorption equilibrium in the range of pH studied. The neutral PCP species showed to have higher binding capacity to pine bark than the anionic PCP, which was reflected in a decrease in the distribution coefficient (Kd) of the linear sorption isotherm with the increase of solution pH from 2 to 7. On the other hand, between 10 degrees C and 35 degrees C, the temperature does not seem to play a significant role in the PCP sorption by pine bark, while the sorbent size is a key parameter to enhance the overall process.     

Phenanthrene sorption/desorption sequences provide new insight to explain high sorption coefficients in field studies

The sorption coefficients obtained in field investigation vary greatly from laboratory sorption experiments. The possible reasons were discussed in literature. Observing the commonly reported desorption hysteresis, this study proposed that the unclear sorption history of the field study could also result in the diverse sorption coefficients. This study conducted a comparative study regarding phenanthrene sorption/desorption behavior in low-concentration multi-time sorption process and the commonly applied high-concentration one-time sorption process. The sorption coefficients determined during the desorption process were much higher than those at sorption process. Thus, the prediction of sorption coefficient should be related with sorption history. Desorption hysteresis was increased with increased equilibration time and decreased solid-phase concentration. In addition, although the apparent contact time between sorbate and sorbent was shorter for low-concentration multi-time sorption, the desorption hysteresis was much stronger, which consequently result in higher sorption coefficients in comparison to high-concentration one-time sorption. Pore swelling or diffusion-controlled sorption kinetics could not explain this phenomenon. This study calls for research attention on sorption history, especially for field investigations.     

Sorption and desorption studies of a reactive azo dye on effective disposal of redundant material

The effective disposal of redundant elephant dung (ED) is important for environmental protection and utilization of resource. The aim of this study was to remove a toxic-azo dye, Reactive Red (RR) 120, using this relatively cheap material as a new adsorbent. The FTIR–ATR spectra of ED powders before and after the sorption of RR 120 and zero point charge (pH_zpc) of ED were determined. The sorption capacity of ED for removing of RR 120 were carried out as functions of particle size, adsorbent dose, pH, temperature, ionic strength, initial dye concentration, and contact time. Sorption isotherm, kinetic, activation energy, thermodynamic, and desorption parameters of RR 120 on ED were studied. The sorption process was found to be dependent on particle size, adsorbent dose, pH, temperature, ionic strength, initial dye concentration, and contact time. FTIR–ATR spectroscopy indicated that amine and amide groups have significant role on the sorption of RR 120 on ED. The pH_zpc of ED was found to be 7.3. Sorption kinetic of RR 120 on ED was well described by sigmoidal Logistic model. The Langmuir isotherm was well fitted to the equilibrium data. The maximum sorption capacity was 95.71 mg?g^?1. The sorption of RR 120 on ED was mainly physical and exothermic according to results of D–R isotherm, Arrhenius equation, thermodynamic, and desorption studies. The thermodynamic parameters showed that this process was feasible and spontaneous. This study showed that ED as a low-cost adsorbent had a great potential for the removal of RR 120 as an alternative eco-friendly process.     

改性荞麦壳对水溶液中Cu~(2+)离子吸附效果及机理

以柠檬酸对荞麦壳进行化学改性,改性后荞麦壳吸附剂对Cu2+的吸附量增加。研究了不同pH、吸附剂投入量、浓度和时间对吸附效果的影响。在pH值为5.5,Cu2+初始浓度50 mg/L,吸附剂投入量为1 g,吸附时间为120 min的条件下,Cu2+的吸附量达到较大值。通过用改性荞麦壳吸附剂对Cu2+的热力学吸附过程的分析,结果表明,改性荞麦壳吸附剂符合Langmuir吸附等温模式,改性荞麦壳吸附剂对Cu2+的吸附存在化学吸附,改性荞麦壳的最大吸附量可以达2.26 mg/g。研究改性荞麦壳吸附剂吸附Cu2+的动力学特性,吸附动力学行为可用准二级速率方程进行很好的描述,准二级吸附速率常数随温度升高而增大。准一级速率方程和颗粒扩散模型可以较好地描述吸附初始阶段,Cu2+浓度较高,颗粒内扩散;吸附后期,Cu2+浓度较低,受到颗粒外扩散的控制。总之,整个吸附过程可能是多种动力学机理共同作用的结果。     

胺化木质素对水中Cu（Ⅱ）、Cd（Ⅱ）的吸附

以胺化木质素作吸附剂对水中Cu2＋、Cd2＋的去除进行了研究，主要考察了吸附时间、溶液pH值、温度和金属离子初始浓度对吸附去除率的影响，并研究了其吸附等温线和动力学。结果表明，胺化木质素能有效去除水溶液中的Cu2＋、Cd2＋，且对Cd2＋的吸附能力大于Cu2＋吸附动力学符合准二级动力学方程，吸附等温线均可以很好地用Langmuir方程描述。