竹炭对溶液中铬(Ⅵ)的吸附特性研究

研究了竹炭对溶液中Cr(Ⅵ)的吸附特性。研究内容包括接触时间、pH、投料量、吸附温度和溶液中铬的初始质量浓度对吸附的影响。结果表明,竹炭能有效地除去水溶液中的铬。在pH3.0~6.2的HAc-NaAc缓冲体系中,竹炭对溶液中的铬均有较大的吸附能力,最佳的吸附酸度为pH 3.5;吸附温度升高,吸附量增大,说明吸附是吸热过程;Freundlich等温吸附模型能较好的描述吸附过程;用NaOH和微波加热法对吸附后的竹炭进行再生试验,竹炭的吸附能力可恢复到原来的98%以上。竹炭可作为理想的除铬吸附的材料。     

竹炭对砷（Ⅲ）离子的吸附行为研究

研究了溶液的pH值与初始质量浓度、竹炭用量、吸附时间以及温度等因素对As（Ⅲ）离子吸附效果的影响。研究结果表明,在pH为3．00和12．50的情况下,竹炭对As（Ⅲ）离子有较好的吸附效果;同时吸附率随初始质量浓度的增加而降低,吸附能在180min内达到吸附平衡;等温吸附服从Freundlieh吸附等温方程式,酸性条件和碱性条件的最佳吸附温度分别为30℃和40℃。认为竹炭可作为理想的除砷吸附材料。     

生物质竹炭对水中Cd~(2+)的吸附行为研究

以竹炭和经化学改性竹炭作为吸附剂,研究其对水溶液中Cd2+的吸附特性,探讨了竹炭对Cd2+的吸附热力学和吸附动力学性质,通过单因子优化实验探讨了温度、竹炭投加量和p H值对吸附效果的影响。结果表明:竹炭及改性竹炭对Cd2+的吸附动力学过程符合准二级动力学模型,在18h可达到平衡;其等温吸附曲线符合Langmuir方程,最大吸附量分别为10.18mg/g和16.71mg/g;两者对Cd2+的吸附受温度的影响较小;竹炭及改性竹炭的最佳投加量分别为0.8g、0.6g;p H对竹炭及改性竹炭吸附Cd2+的影响较大,在p H 2~6范围时,竹炭及改性竹炭对Cd2+的吸附量随p H的增加而增加。     

活性氧化铝及其再生氧化铝对水中氟离子的吸附（英文）

水的氟污染是全世界普遍存在的问题,因此受到了人们的极大关注。我们研究重点是使用活性氧化铝及再生后的活性氧化铝脱除水中的氟离子。为了得到合适的吸附剂,我们将工业薄水铝石在573 K至1473 K范围内进行煅烧,并对其进行表征。从X射线衍射图中可以看出,当煅烧温度在773 K至1473 K之间时,样品转化为γ-氧化铝(活性氧化铝)。且BET数据显示,当煅烧温度在773K至1473K之间时,样品的比表面积逐渐降低。在本实验中,我们选用773K、873K、973 K煅烧的活性氧化铝作为除氟吸附剂,同时选用动态吸附法移除水中的氟离子。突破曲线表明吸附容量随着煅烧温度的增加而降低。为了研究氟离子的初始浓度对吸附容量的影响,我们选用15 mg·L~(-1)、20 mg·L~(-1)、25 mg·L~(-1)的氟离子溶液作为初始溶液,且吸附剂的吸附容量随着初始浓度的增加而增加。当活性氧化铝吸附氟离子达到饱和后,用pH值为13.0、13.3和13.5的氢氧化钠溶液对其再生,并用0.1 mol·L~(-1)的盐酸溶液对其进行活化以提高吸附剂的吸附能力。通过比较五次再生过程中的解吸率和铝溶解率,可以看出pH值为13.0的氢氧化钠溶液最适合作解吸剂。通过分析吸附剂的氮气吸-脱附等温线,发现再生后的吸附剂的氮气吸脱附等温线的形状并没有发生很大的变化,说明再生过程中吸附剂的孔结构并没有被破坏。五次再生过程中吸附剂的比表面积和等电点的变化是影响吸附容量很重要的两个因素,发现吸附剂再生后其比表面积和等电点均增加。为检测再生吸附剂的吸附效果,每次再生后都需要进行一次吸附实验。突破曲线表明,和初始活性氧化铝相比,再生后达到饱和所用的时间更短,吸附量越大。为了探究吸附机理,我们用红外光谱表征吸附剂中的羟基,发现再生过程中吸附剂中Al―O―H含量的变化是影响活性氧化铝对氟离子吸附量的关键因素。     

铝改性赤泥吸附剂的制备及其除氟效能的研究

以铝工业废矿渣为原材料,通过铝盐改性及焙烧活化处理,制备了水中除氟吸附剂。研究考察了吸附剂吸附氟能力、反应时间、pH值以及投加量对吸附效果的影响。结果表明,铝改性赤泥吸附剂具有较好的除氟效果,未焙烧铝改性赤泥吸附剂及经过200 ℃焙烧活化赤泥吸附剂的饱和吸附量分别达到68.07和91.28 mg·g^-1,远高于原状赤泥的饱和吸附量13.46 mg·g^-1。经吸附后出水氟含量低于1 mg·L^-1的国家饮用水标准。吸附规律符合Langmuir等温方程,溶液pH值显著影响除氟效果,在溶液pH值为7~8时达到最佳去除效果。     

粉煤灰合成Na-P1沸石去除饮用水中氟的研究

采用水热法合成了Na-P1型粉煤灰沸石,改性后用于去除饮用水中的氟离子。研究了吸附时间、沸石用量、氟离子浓度对除氟率的影响,探讨了沸石除氟的吸附机理。研究表明,将粉煤灰沸石用1.0%的NaOH溶液浸泡12 h,然后用2.0%的硫酸铝钾溶液浸泡36 h活化,能够明显提高其吸附除氟能力。在考察的范围内,除氟率随吸附时间的延长和沸石用量增多而增加。吸附等温线拟合结果表明,吸附除氟过程符合Langmuir吸附等温式。     

改性高分子除氟吸附材料的研究进展

饮用水中氟离子超标对人体造成严重危害。吸附法是目前氟污染水体处理方法中较经济理想的分离技术,开发经济、高效、易再生的新型吸附材料是目前水体除氟重点研究的方向。其中,高分子吸附材料是最受研究者关注的除氟吸附剂种类之一。结合近年来的研究工作,本文综述了导电高分子类、生物高分子类以及树脂类高分子吸附剂的合成和改性方法,及不同改性高分子对水中氟离子的吸附性能和除氟机理,并对今后高分子类除氟吸附材料的发展提出展望。     

竹炭-泡沫塑料复合材料对甲醛吸附性能的研究

考察了竹炭-泡沫塑料复合材料(ZP)对甲醛蒸汽的吸附量,研究了ZP中竹炭含量和吸附时间对甲醛吸附量的影响。结果表明:吸附时间2 h时,ZP-2(含竹炭5%)对甲醛的吸附量为7.157 mg.g-1,ZP-6(含竹炭25%)的吸附量增至11.913 mg.g-1;吸附时间为48 h时,ZP-2的吸附量为15.321 mg.g-1,ZP-6的吸附量增至28.668 mg.g-1。运用扫描电子显微镜(SEM)观察了竹炭与泡沫塑料的结合形态,初步解释了ZP对甲醛吸附性能变化的微观影响因素。采用SPSS软件以吸附时间、竹炭含量为变量对甲醛吸附量进行回归分析,得出回归方程为:Y=3.94×Ln(X1)+30.56×(X2)+1.7,相关系数R2=0.95。表明随着吸附时间(X1),竹炭含量(X2)的增加,ZP对甲醛的吸附量(Y)逐渐增大,ZP能够有效地吸附甲醛。     

改性竹炭对含铅废水吸附处理的效果研究

研究了商用竹炭和改性竹炭对含铅废水的吸附处理的实验条件及效果。结果表明,对一定质量浓度及一定量含铅废水处理时,只要条件和吸附剂竹炭的投放量合适,铅的去除率均可达99.9%以上。以我国饮用水卫生标准中铅含量≤0.05mg/L为标准,根据废水中铅的含量,给出了吸附处理所需吸附剂投料量的估算方法和实验验证结果,为竹炭在含铅废水处理中的应用提供理论依据。     

一维纳米炭/竹炭的制备及其对Pb~(2+)的吸附

以二甲苯为炭源、二茂铁为催化剂,采用CVD法在竹炭上催化气相生长了一维纳米炭,采用扫描电镜、透射电镜及氮吸附仪等对一维纳米炭/竹炭的形貌、微结构及比表面积进行了表征,并研究了一维纳米炭/竹炭复合材料对重金属离子Pb2+的吸附性能.结果表明,采用CVD法可以在竹炭上生长一维纳米炭,且随着气相生长时间的延长,竹炭上的一维纳米炭变得更加浓密而均匀.竹炭上生长一维纳米炭后,对Pb2+的吸附能力增强,硝酸氧化处理可以进一步提高一维纳米炭/竹炭对Pb2+的吸附能力.     

ADSORPTION OF CHLOROFORM AND TRICHLOROETHYLENE IN WATER WITH A NEW KIND OF HYPERCROSSLINKED RESINS

In this paper two newly developed hypercrosslinked resins were used to treat micropolluted drinking water and their static and kinetic adsorption were investigated at 293 K. The results show that these two adsorbents are superior to Amberlite XAD-4 for removing chloroform and trichloroethylene in aqueous solutions. The breakthrough capacity and the total capacities from mini-column adsorption studies for chloroform and trichloroethylene on XAD-4, ZH-01 and ZH-00 are calculated respectively under experimental conditions     

Fluoride removal from water by chitosan derivatives and composites: A review

Fluoride is an essential element, indispensable for maintenance of dental health. Nevertheless, fluoride concentrations in drinking water above 1.5 mg L⁻¹ may be detrimental to human health. Many methods have been developed for removing excessive fluoride from drinking water, adsorption seems to be an effective, environmentally friendly and economical one. Since the sorption capacity of fluoride below 2 mg L⁻¹ on most conventional adsorbents is not satisfactory, much effort has been devoted to develop new and cost-effective fluoride adsorbents. This review reports the recent developments in the F⁻ removal in water treatment, using chitosan derivatives and composites in order to provide useful information about the different technologies. When possibly the adsorption capacity of chitosan derivatives and composites under different experimental conditions is reported to help to compare the efficacy of the fluoride removal process. A comparison with the adsorption capacity of other low cost adsorbents is also tabled.     

由单层薄水铝石制备的活性氧化铝处理水中氟离子

The preparation of high-efficiency and low-cost adsorbents for the defluoridation of drinking water remains a huge challenge. In this study, single-layer and multi-layer boehmite were first synthesized via an organic-free method, and active alumina used for fluoride removal from water was obtained from the boehmite. The advantage of a single layer is that more aluminum is exposed to the surface, which can provide more adsorption sites for fluoride. The active alumina adsorbent derived from single-layer boehmite exhibits a high specific surface area and excellent adsorption capacity. The high surface area ensures a high adsorption capacity, and the organic-free synthesis method lowers the preparation cost. The as-prepared adsorbent was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier-transform infrared spectroscopy (FTIR) and nitrogen adsorption-desorption analysis. The single-layer structure of boehmite was determined from the simulated XRD diffraction pattern of single-layer boehmite. The disappearance of the (020) diffraction peak of boehmite illustrates that the dimensions in the b direction are extremely small, and according to the XRD simulation results, the single-layer structure of boehmite could be determined. Single-layer boehmite with a surface area of 789.4 m²·g^-1 was formed first. The active alumina obtained from the boehmite had a surface area of 678.4 m²·g^-1, and the pore volume was 3.20 cm³·g^-1. The fluoride adsorption of the active alumina was systematically studied as a function of the adsorbent dosage, contact time, concentration, co-existing anions, and pH. The fluoride adsorption capacity of the active alumina obtained from the single-layer boehmite reached up to 67.6 mg·g^-1, which is higher than those of most alumina adsorbents reported in the literature. The adsorption capacities of the active alumina are related to the specific surface area and the number of hydroxyl groups on the surface. Dosages of 0.6, 1.0, and 2.6 g·L^-1 of active alumina were able to lower the 10, 20, and 50 mg·L^-1 fluoride solutions, respectively, below the maximum permissible limit of fluoride in drinking water in China (1.0 mg·L^-1), suggesting that the active alumina synthesized in this work is a promising adsorbent for defluoridation of drinking water. In addition, the fluoride adsorption is applicable in a wide pH range from 4 to 9 and is mainly interfered by SO₄^2- and PO₄^3-. Further investigation suggested that the fluoride adsorption of the active alumina follows the pseudo second-order model and Langmuir isotherm model     

Studies on fluoride adsorption capacities of amorphous Fe/Al mixed hydroxides from aqueous solutions

This study evaluated the effectiveness of amorphous iron and aluminum mixed hydroxides in removing fluoride from aqueous solutions. A series of mixed Fe/Al samples were prepared at room temperature by co-precipitating Fe and Al mixed salt solutions at pH 7.5. The compositions (Fe:Al molar ratio) of the oxides were varied as 1:0, 3:1, 2:1, 1:1 and 0:1 and the samples were characterized by XRD, BET surface area and pH_ZPC. The XRD studies indicated the amorphous nature of the samples and Al(III) incorporation on Fe(III) hydroxides. Batch adsorption studies for fluoride removal on these materials showed that the adsorption capacities of the materials were highly influenced by solution pH, temperature and initial fluoride concentration. The rate of adsorption was fast and equilibrium was attained within 2 h. The adsorption followed first-order kinetics with intraparticle diffusion as the rate determining step for all the samples. The experimental data fitted well to both Langmuir and Freundlich adsorption isotherms. All samples exhibited very high Langmuir adsorption capacities; the sample with molar ratio 1 has shown maximum adsorption capacity of 91.7 mg/g. The thermodynamic parameters were determined to study the feasibility of the adsorption process.     

Adsorption of fluoride ions onto carbonaceous materials

The characteristics of fluoride ion adsorption onto carbonaceous materials were derived as adsorption isotherms at different temperatures and in different pH solutions. The fluoride ion was adsorbed into pores in carbonaceous materials produced from wood; the larger the specific surface area, the more fluoride ions adsorbed. Bone char was the most effective adsorbent. The composition of bone char includes calcium phosphate, calcium carbonate, and so on. This suggests that the phosphate ion in bone char was exchanged with a fluoride ion. Moreover, the mechanism of fluoride ion adsorption onto bone char is clearly chemical in nature because the amount of fluoride ion adsorbed onto bone char increased with increasing temperature and decreasing pH. The amount of fluoride ion adsorbed onto bone char was also shown to depend on the concentration of sodium chloride in solution because of the "salting-out" effect. The adsorption of fluoride ion onto bone char is endothermic. Bone char can be utilized to remove fluoride ions from drinking water.     

Soil adsorption defluoridation of drinking water for an Ethiopian rural community

Content of fluoride compounds in some typical Ethiopian water sources was analysed and several commonly available soils were characterized for their adsorption properties regarding the water defluoridation. Various soils were collected in different Ethiopian sites and the samples were analysed by X-ray diffractometry for their mineralogical composition. Batch experimental runs at room temperature were performed to evaluate the adsorption capacity of each soil sample as well as to deduce the adsorption isotherms of fluoride ions with respect to the examined soils. The best soil was identified in terms of adsorption capacity and considered for the design of two different adsorption apparatuses. Considering the water consumption of a small rural community, the capacity of the adsorption unit was selected to assure a reduction of the fluoride concentration in drinking water to the limits recommended by the World Health Organization and to allow a suitable working time of the adsorption unit before the replacement of adsorbent would be necessary. Presented at the 33rd International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 22–26 May 2006.     

Adsorption of fluoride from aqueous solution by graphene

A batch adsorption system was applied to investigate the adsorption of fluoride from aqueous solution by graphene. The adsorption capacities and rates of fluoride onto graphene at different initial pH, contact time, and temperature were evaluated. The experimental results showed that graphene is an excellent fluoride adsorbent with an adsorption capacity of up to 17.65 mg/g at initial fluoride concentration of 25 mg/L and temperature of 298 K. The isotherm analysis indicated that the adsorption data can be well described by Langmuir isotherm model. Thermodynamic studies revealed that the adsorption reaction was a spontaneous and endothermic process.     

Removal of aqueous As(III) and As(V) by hydrous titanium dioxide

Dissolved arsenic in drinking water is a global concern as it causes serious health problems. The purpose of this research was to study the applicability of an industrial intermediate product, a mixture of titanium hydroxide and titanium dioxide for removing aqueous arsenic. The material is common, inexpensive, and non-toxic, making it an attractive choice for drinking water purification. The kinetics and equilibrium of removing both primary inorganic arsenic forms, As(III) and As(V), were studied by separate batch experiments. The tested material functioned well in removing both of these arsenic forms. The apparent values for Langmuir monolayer sorption capacities were 31.8 mg/g for As(III) and 33.4 mg/g for As(V) at pH 4. The studied TiO(2) performed the best in acidic conditions, but also reasonably well in other pH conditions.     

Sources and toxicity of fluoride in the environment

Fluoride, a naturally occurring element, exists in combination with other elements as a fluoride compound, and is found naturally in water, foods, soil, and several minerals such as fluorite and fluorapatite. Fluoride normally enters the environment and human body through water, food, industrial exposure, drugs, cosmetics, etc. However, fluoride (F^?) contamination in groundwater has been recognized as a serious problem worldwide. The World Health Organization’s specified tolerance limit of fluoride in drinking water is 1.5 mg/L. Human disease caused by fluoride manifests itself in three forms: dental, skeletal, and non-skeletal fluorosis. Apart from teeth and bones, the interaction and involvement of soft tissues, organs, and other systems of the body with fluoride leads to non-skeletal fluorosis. It leads to many bone diseases, mottling of teeth, and lesions of the endocrine glands, thyroid, liver, kidney, and other organs. Fluoride ion concentration in drinking water can be easily estimated by UV-Vis spectrophotometer. Various defluoridation techniques have been developed to reduce the fluoride content to the desired level including principally membrane and adsorption processes. Biosorption is still one of the most extensively used methods for defluoridation of drinking water due to it being cost-free or low cost and because of its viability.     

Determination of fluoride in drinking water and in urine of adolescents living in three counties in Northern Chihuahua Mexico using a fluoride ion selective electrode

This study was carried out to determine fluoride in drinking water and in urine of adolescents, ages 15-20 years, living in Northern Chihuahua Mexico. Participants are from a cross-sectional study on health effects of chronic fluoride exposure from drinking water. A total of 201 participants (106 female and 95 male) in the study were recruited from three counties. Samples of drinking water of each county were collected and analyzed using the U.S. EPA Fluoride Ion-Selective Method. Statistically significant difference of fluoride content in water was found among the three counties of recruitment (Cd. Juarez; 0.3 mg/L, Samalayuca, 1.0 mg/L, and Villa Ahumada, 5.3 mg/L). Fluoride content in wells and tap water samples of Villa Ahumada ranged from 5.0 to 5.7 mg/L. Fluoride content of these samples was above the level permitted by Mexican regulations. The fluoride content in bottled water obtained from local stores in Villa Ahumada ranged from 0.3 to 3.7 mg/l.Fluoride in urine samples of each participant was also analyzed using the U.S. EPA Ion-Selective Method. The mean fluoride urine concentration (reported in mg/g creatinine) in adolescents living in these counties was 0.792±0.39, 1.33±0.67 and 2.22±1.16 (Cd. Juarez, Samalayuca and Villa Ahumada), respectively. The high fluoride urinary levels found in participants from Villa Ahumada may be associated to the high fluoride level (5.3 mg/L) in dinking water.The accuracy of measurements was assessed with reference materials in water and in urine. Mean fluoride recovery was 99.0% and 99.6% in water and in urine, respectively. The levels obtained were within the assayed 5% confidence levels.