Removal of diuron and amitrole from water under static and dynamic conditions using activated carbons in form of fibers, cloth, and grains

This study investigated the removal of the herbicides diuron and amitrole from water under static and dynamic conditions using different activated carbons in the form of fibers, cloth, and grains. In all cases, there was much greater adsorption of diuron than of amitrole due to the lower solubility, greater hydrophobicity, and larger dipolar moment of the former. The activated carbon cloth was the best adsorbent for diuron under dynamic conditions because it had the largest mesopore volume, water-accessible pore volume, and surface area. However, the best adsorbent for amitrole under dynamic conditions was the granular activated carbon due to its higher surface basicity. Comparisons using the best adsorbent for each herbicide showed that diuron was removed by the activated carbon more efficiently compared with amitrole under both dynamic and static conditions.     

Layered double hydroxide of cobalt-zinc-aluminium intercalated with carbonate ion: preparation and Pb(II) ion removal capacity

Ternary layered double hydroxide (Co–Zn–Al LDH) intercalated with carbonate was synthesised via a simple co-precipitation method at pH ≥10. It was characterised using the Fourier transform infrared (FTIR) spectrometer, X-ray diffractometer (XRD), surface area and porosity analyser, Thermo-gravimetric/differential thermal analysis (TGA–DTA), and Scanning Electron Microscope (SEM). The Pb(II) adsorption properties, mechanism, and possible reuse of the LDH were also investigated by the batch technique. The characterisation results showed the presence of hydroxyl group as well as the intercalated carbonate anions within the well-defined LDH crystal structure. The TGA-DTA results confirmed the presence of these anionic groups which were liberated from the structure at ≈200 and 300°C, respectively. The LDH-specific surface area, pore diameter and width are 54.0 m²/g, 41.3 and 25.1 nm, respectively. Adsorption results showed that Pb(II) equilibrium could be achieved in 120 min, and adsorption increased with concentration and temperature. A Pb(II) adsorption capacity of 130.34 mg/g was reached for this LDH, and the adsorption process was spontaneous, endothermic and mainly electrostatic with most of the adsorption occurring within the pores. Desorption test suggested that approximately 90% of the adsorbed Pb(II) could be desorbed; hence, the Co–Zn–Al–CO₃ LDH may be reused.     

Adsorption of Cu(II) and Pb(II) onto a grafted silica: isotherms and kinetic models

The isotherms and kinetics of adsorption of lead(II) and copper(II) onto a grafted silica are studied at 20 degrees C. A commercial silica is grafted with an ethylediamine derivative, N-[3-(trimethoxysilyl)propyl]-ethylenediamine. From the Langmuir isotherms, maximum adsorption capacities of the grafted silica towards Pb(II) and Cu(II) are determined (0.184 mmol Pb(II)g-1 and 0.261 mmol Cu(II)g-1) and compared to those of non-modified silica (respectively, 0.019 and 0.036 mmol g-1). Four kinetic models, i.e., pseudo-first order, pseudo-second order, Langmuir and double-exponential are applied to fit the experimental kinetic data. The kinetic parameters are determined which allow to calculate the theoretical metal uptake as a function of time. The results are discussed and indicate the best fit is obtained with the double-exponential model. A discussion on the adsorption mechanism with respect to the double-exponential model leads to two possible interpretations: the metal uptake may follow a diffusion-controlled mechanism or a two-site adsorption process.     

Adsorption of organic compounds onto activated carbon

Adsorption isotherms of acetone, propionaldehyde, methylisobutylketone and sucrose from aqueous solutions onto granular activated carbon have been determined.Multi-solute data have been compared with the theoretical prediction obtained from ideal adsorbed solution model.The agreement between calculated and observed results is satisfactory. Only the system sucrosemethylisobutylketone shows significant deviation between experimental and predicted values. Therefore the model can be successfully utilized in design of activated carbon units.     

粉末活性炭处理反渗透浓水的吸附模型

粉末活性炭(PAC)可显著吸附去除反渗透(RO)浓水中的COD和UV254,使其能够达标排放或进一步资源化.首先通过正交实验选择主要吸附影响因素及其水平范围,再通过单因素实验确定COD和UV254的吸附等温线和吸附动力学方程,最后通过响应曲面法(RSM)实验建立了去除COD和UV254的吸附模型,模型中以PAC投量和吸...     

不同锰砂滤料除锰吸附特性研究

为了掌握不同锰砂滤料处理锰离子超标地下水时的吸附特性,选择4种有代表性的锰砂滤料对同一原水进行静态吸附试验,研究了不同锰砂对水中锰离子的吸附情况;分别与Langmuir吸附等温式和Freundlich吸附等温式进行拟合,根据可决系数R2值判断出4种锰砂均符合Langmuir吸附模型;以Langmuir吸附模型中的最大吸附容量qmax与吸附能量常数KL反映吸附剂的吸附能力,综合分析得出B组马山高品质锰砂的吸附效果最好,并由此得出MnO2质量分数与锰砂吸附能力呈正相关.该研究可为实际工程中的锰砂选择提供科学依据,具有实际意义.     

Equilibrium studies during the removal of dyestuffs from aqueous solutions using Bagasse pith

The adsorption of four dyestuffs, namely, Basic Blue 69 (BB69), Basic Red 22 (BR22), Acid Red 114 (AR114) and Acid Blue 25 (AB25), onto bagasse pith has been studied. Bagasse pith is a cheap, abundant waste product from the sugar industry in Egypt and was found to have the following monolayer equilibrium saturation capacities: 158, 77, 23 and 22 mg dye g⁻¹ pith.

The effects of pith particle size range and dye solution temperature were studied. The equilibrium data were analysed using Langmuir, Freundlich and Jossens isotherms.     

粉末活性炭对水中呋喃丹的吸附性能研究

考察了粉末活性炭吸附去除水中呋喃丹的可行性,并采用Freundlich公式拟合去离子水和自来水条件下的吸附等温方程.结果表明,采用粉末活性炭可有效去除水中的呋喃丹,在去离子水条件下,呋喃丹初始质量浓度为0.035 mg/L,投炭量为20 mg/L,吸附时间为120 min时,呋喃丹的去除率大于98％.根据吸附等温方程计...     

Adsorption of non-ionic surfactants on activated carbon and mineral clay

A series of non-ionic surfactants of nonyl-phenol ethoxylates, with n = 4?23;0 ethylene oxide groups and dinonyl-phenol ethoxylate were studied in dilute aqueous solution. Their removal efficiencies and mechanisms by adsorption on powdered and granular activated carbon and on Na-montmorillonite clay were investigated. The powdered activated carbon proved to be the most efficient with 94–100% non-ionic surfactants removal by addition of 40–80 mg activated carbon.Various models of adsorption isotherms such as Langmuir, BET and S-type were used to determine Q⁴, the limiting adsorption capacity. The relationships between Q^o and parameters affecting the adsorption of non-ionic surfactants such as n, HLB and CMC were determined. The cross-sectional area σ₀ occupied by surfactant molecules on the adsorbent was calculated. Adsorption has been proven to be a potential advanced physicochemical treatment method for the effective removal of non-ionic surfactants present in effluents intended for reuse.     

可再生吸附法脱除冷凝液中有机物中试研究

为了解决石油化工生产过程中所产冷凝液被有机物污染而难以回用的难题,对烯烃生产过程中产生的冷凝液进行了水质分析,在明确冷凝液中主要有机物组成的基础上,开发了一套可再生吸附脱除冷凝液中有机物的处理技术.中试结果表明,在吸附材料填充率为75%、水力流速为20 m/h的条件下,采用下向流进水方式,该系统可有效脱除冷凝液中的有机物,出水TOC<1.0 mg/L,完全能满足二级脱盐水对总有机碳的控制要求.     

Adsorption of nitrophenol onto activated carbon: isotherms and breakthrough curves

The adsorption isotherm of p-nitrophenol onto granular activated carbon in 25 degrees C aqueous solution was experimentally determined by batch tests. Both the Freundlich and the Redlich-Peterson models were found to fit the adsorption isotherm data well. A series of column tests were performed to determine the breakthrough curves with varying bed depths (3-6 cm) and water flow rates (21.6-86.4 cm3/h). Explicit equations for the breakthrough curves of the fixed-bed adsorption processes with the Langmuir and the Freundlich adsorption isotherms were developed by the constant-pattern wave approach using a constant driving force model in the liquid phase. The results show that the half breakthrough time increases proportionally with increasing bed depth but decreases inverse proportionally with increasing water flow rate. The constant-pattern wave approach using the Freundlich isotherm model fits the experimental breakthrough curves quite satisfactorily. A correlation was proposed to predict the volumetric mass-transfer coefficient in the liquid phase successfully. The effects of solution temperature and pH on the adsorption isotherm were also studied and the Tóth model was found to fit the isotherm data well at varying solution temperatures and pHs.     

Combined effect of carbon dosage and initial adsorbate concentration on the adsorption isotherm of heavy metals on activated carbon

The adsorption of dissolved chromium and lead ions by powdered activated carbons significantly depends on the pH, initial adsorbate concentration and carbon dosage. Freundlich and Langmuir equations were unable to describe adequately the observed isotherms under the combined influence of both the carbon dosage and initial adsorbate concentration. These equations were modified and the resulting equations were found to correlate well with the experimental equilibrium data. The modified Langmuir equation gave an overall mean ratio of calculated to experimental adsorptive capacity of 1.001 compared with 1.046 given by the modified Freundlich equation for a total of 135 sets of equilibrium data obtained at different carbon dosages and initial adsorbate concentrations.     

富氧空调的可行性探讨

空调环境的氧含量普遍低于20.9%,有必要采取措施补充空调环境消耗的氧气,改善室内空气质量。简要介绍了几种制氧方法,提出将变压吸附制氧或膜分离制氧用于空调环境增氧的思路,并且描述了这两种增氧系统。以某体育场馆为例,对两种增氧系统与传统的增大新风量增氧方式进行了比较,认为前者在设备初投资和运行成本上都具有优势,而且能够满足空调环境的增氧要求。     

粉末活性炭对马拉硫磷的吸附性能研究

以马拉硫磷作为突发性污染物,考察了粉末活性炭对其的吸附效果。试验结果表明,粉末活性炭对纯水和滤后水中的马拉硫磷均具有较好的去除效果,对前者的去除效果更为明显,去除率随活性炭投加量的增加而升高。当马拉硫磷浓度为1.25 mg/L,纯水、滤后水中的活性炭投加量分别为12.0和20 mg/L时,反应120 min后马拉硫磷剩余浓度均低于0.25 mg/L。对滤后水而言,药剂费用约为0.06～0.08元/m3。     

From potential absorptive capacity to innovation outcomes in project teams: The conditional mediating role of the realized absorptive capacity in a relational learning context

Starting from the construct absorptive capacity, this study separately treats its two dimensions – potential absorptive capacity (PACAP) and realized absorptive capacity (RACAP) – and analyzes their influence on innovation outcomes (IO) in project teams. We also examine potential absorptive capacity as an antecedent of realized absorptive capacity. In addition, we propose that relational learning (RL) will play a moderator role reinforcing the PACAP and RACAP link. Consequently, this paper builds and tests a conditional process model. Data was collected from a sample of 110 project managers of firms belonging to the Spanish automotive components manufacturing sector. Results from variance-based structural equation modeling and PROCESS tool show that RACAP fully mediates the influence of the PACAP on IO, and this indirect effect is positively conditioned by RL. This paper provides evidence that when RL achieves a low value, this indirect influence is not different from zero.     

Experimental study on adsorption capacity of an activated carbon-based adsorption water chiller

The objective of this study was to evaluate the adsorption capacity of a working pair for an adsorption water chiller. Activated carbon fibre–methanol, activated carbon fibre–ethanol and activated carbon pallet–ethanol were used as an adsorbent–adsorbate pair in this study. The experiment was conducted using a stainless steel adsorber, 110?mm diameter by 150?mm height, filled with adsorbent and transparent plastic evaporator, 100?ml capacity, filled with adsorbate. The experiment was performed by isobaric adsorption in the temperature range of 10–100°C at the evaporator temperature of 20°C (water chiller). An experimental investigation showed that the activated carbon fibre–methanol pair has the highest adsorption capacity (0.44?kg/kg) compared to the activated carbon fibre–ethanol and activated carbon pallet–ethanol pairs. The finding revealed that uniform structure and large surface area of adsorbent as well as low boiling point and large latent heat of adsorbate had highly significant effects on adsorption capacity. The effect of time and adsorber temperature on adsorption capacity is also discussed in this study.     

灰色理论在单桩极限承载力预测中的应用

根据灰色系统理论模型,对桩的静载荷试验P-S曲线数据进行分析处理,预估单桩竖向极限承载力,并通过实例加以验证,指出灰色预测理论的预测结果与设计计算结果相符合,可为人们对桩的极限受力情况提供一种新的认识角度和解决问题的方法。     

PC变截面空心板桥承载力评估及寿命预测

根据国内外研究现状,结合依托工程桥梁检测结果,对旧桥承载力进行了总结和评估,在项目纽已有的研究基础上,对PC变截面空心板使用寿命进行了研究,以便指导今后的设计、施工、养护。     

Monitoring the role of aceticlasts in anaerobic digestion: activity and capacity

Aceticlastic methanogens are seen as a key to digester capacity and stability. This paper develops and applies an assay to measure digester stability by measuring the maximum aceticlastic methane production rate (V_max,ac). The V_max,ac in combination with acetate concentrations was found to be an effective digestion monitoring tool to indicate process upsets. At steady state, thermophilic, first stage and short SRT digesters generally had a greater V_max,ac than mesophilic, second stage or long SRT digesters. The ratio of the V_max,ac to the plant aceticlastic methane production rate, termed the Acetate Capacity Number (ACN), is a measure of the excess capacity of the digester. Either V_max,ac or ACN can be used to estimate the capability to handle higher organic loading rates. Monod modeling was used to predict V_max,ac, ACN and maximum VS loading rates for mesophilic and thermophilic digestion and for staged digesters to better understand expected digestion capacity and stability.     

Adsorption of phenol from an aqueous solution by selected apatite adsorbents: kinetic process and impact of the surface properties

Batch adsorption experiments were conducted to investigate the removal of phenol from wastewater by addition of three apatites (porous hydroxyapatite (PHAp) and crystalline hydroxyl- (HAp) and fluoroapatite (FAp)). The best performances were obtained with porous hydroxyapatite PHAp, which presented higher adsorption capacities (experimental: 8.2 mg g⁻¹; calculated 9.2 mg g⁻¹) than HAp and FAp (3-4 mg g⁻¹). Different models of adsorption were used to describe the kinetics data, to calculate corresponding rate constants and to predict the theoretical capacities of apatite surfaces for phenol adsorption. A mechanism of phenol adsorption associating chemisorption and physisorption processes is presented allowing the discussion of the variations in adsorption behavior between these materials in terms of specific surface area and chemical composition. These data suggest that apatites are promising materials for phenol sorption.