磺化褐煤对废水中Cr（Ⅵ）离子的吸附原与还原

在静态条件下，进行了以磺化褐煤作吸附剂、还原剂净化含铬铬废水的实验。研究了含铬废水的ＰＨ值、浓度和接触时间等因素对ＳＢＣ吸附、还原Ｃｒ（Ⅵ）的影响，确定了ＳＢＣ将化含铬废水的最佳条件。结合对实际含Ｃｒ（Ⅵ）废水的吸附、还原净化处理，讨论了ＳＢＣ对电镀废水处理的可行性。     

磺化褐煤对重金属离子的吸附作用研究

在静态条件下,研究了磺化褐煤（ＳＢＣ）对重金属的吸附与交换。结果表明,ＳＢＣ对重金属离子具有较强的吸附性能,ＰＨ值是影响吸附的主要因素,离子交换和表面络合反应是主要吸附形式。结合对实际镀锌废水的吸附净化试验,讨论了ＳＢＣ对电镀废水处理的可行性。     

改性褐煤活性焦对含铬(Ⅵ)废水的处理

为了开发新型高效廉价的废水Cr(Ⅵ)吸附材料,以褐煤为原料制备褐煤活性焦,加入金属氧化物MnO2对褐煤活性焦进行改性,在25℃,静态条件下,探讨了改性褐煤活性焦对含Cr(Ⅵ)废水的处理效果,确定最佳吸附条件,并研究了25℃下的吸附平衡。结果表明:在25℃,废水pH值为2.0,Cr(Ⅵ)的起始浓度为50mg/L,吸附时间为2.0 h,Cr(Ⅵ)与改性褐煤活性焦的质量比为1∶36时,改性褐煤活性焦对废水中Cr(Ⅵ)具有很好的吸附性能;改性褐煤活性焦处理含Cr(Ⅵ)废水的效果显著,饱和吸附量为57.14 mg/g;该改性褐煤活性焦可再生利用。     

壳聚糖吸附处理废水中的微量铬(Ⅵ)

在静态条件下，研究了壳聚糖(CHT)对Cr(Ⅵ)的吸附，探讨了CHT吸附Cr(Ⅵ)离子的最佳工艺条件及CHT的再生方法。结果表明，CHT对Cr(Ⅵ)具有较好的吸附性能，吸附的最佳条件是：pH值3—4；废水中Cr(V1)离子浓度≤60mg／L；吸附时间8—10h。利用CHT处理电镀厂含Cr(Ⅵ)废水，Cr(Ⅵ)离子吸附率达98％以上，且不影响水的本底浓度。     

提取腐植酸后的天祝褐煤残渣对污水中Cr(Ⅵ)的吸附性能

天祝褐煤资源丰富,其提取腐植酸后的残渣对污水中的有害物质有一定的吸附能力.为此,制备了天祝褐煤提取腐植酸后的残渣,研究了其对污水中重金属离子Cr(Ⅵ)的吸附性能.结果表明:在室温(20～25℃),pH值为5的条件下,褐煤残渣对Cr(Ⅵ)有较好的吸附性能,吸附平衡时间约为4 h;吸附规律符合Freundlich吸附等温式,其相关系数R2为0.968 6,特性常数n为2.044 6,其吸附过程可用Ho准二级反应动力学模型描述.     

高温改性凹凸棒石对Cr(Ⅵ)的吸附研究

将凹凸棒石经低温煅烧改性,得到一种改性凹凸棒石材料,以提高凹凸棒石的吸附性能,通过BET(比表面积分析)和FT-IR(红外光谱仪)等实验技术及吸附含铬离子废水来袁征凹凸棒石的性能.实验结果表明高温改性可以提高凹凸棒石的比表面积及其吸附性能;当改性温度为350℃时,可以获得最大的比表面积为140.7m2/g.当凹凸棒石用量为10g/L、溶液pH为2,吸附时间为1h,去除率可以达到98％.     

城市污泥改性物对电镀废水中Cr(Ⅵ)的吸附研究

在静态条件下,进行了以城市污泥改性物(MSMP)作吸附剂净化含Cr(Ⅵ)废水的试验.研究了含Cr(Ⅵ)废水的pH值、浓度、接触时间和吸附剂的投加量等因素对MSMP吸附Cr(Ⅵ)的影响,确定了MSMP净化含Cr(Ⅵ)废水的最佳条件为:吸附时间20 min,pH值为中性,Cr(Ⅵ)起始浓度不超过50 mg/L,温度为30℃.结合对实际含Cr(Ⅵ)废水的吸附净化处理,证实了MSMP可用于电镀废水中Cr(Ⅵ)的吸附处理.     

用磺化泥炭吸附铬(Ⅵ)的热力学特性研究

在静态条件下,研究了水溶液中磺化泥炭吸附铬(Ⅵ)的热力学特性,测定了不同温度下磺化,泥炭吸附铬(Ⅵ)的吸附等温线.结果表明,在稀溶液中磺化泥炭吸附铬(Ⅵ)基本符合Langmuir模型,由于磺化泥炭的微孔结构和表面存在含氧功能团的吸附中心,溶液中的铬(Ⅵ)主要以HCrO-4的形式被磺化泥炭吸附,导致水分子的脱附及H 的产生,从而使热力学函数△So增加.     

天祝褐煤对重金属离子的吸附特征

以甘肃天祝褐煤作吸附剂，常温下对Pb^2＋、Cd^2＋、Zn^2＋、Cu^2＋溶液进行了吸附试验研究，探讨了其吸附动力学、吸附平衡、吸附机理及介质酸度的影响.结果表明，褐煤对几种重金属离子的吸附平衡基本符合Langmuir模型，介质酸度对吸附效果有显著的影响，pH〉5．00时吸附率均可达90％。     

提取腐植酸后的天祝褐煤残渣对污水中Cr(VI)的吸附性能

天祝褐煤资源丰富,其提取腐植酸后的残渣对污水中的有害物质有一定的吸附能力。为此,制备了天祝褐煤提取腐植酸后的残渣,研究了其对污水中重金属离子Cr(Ⅵ)的吸附性能。结果表明:在室温(20～25℃),pH值为5的条件下,褐煤残渣对Cr(VI)有较好的吸附性能,吸附平衡时间约为4h;吸附规律符合Freundlich吸附等温式,其相关系数R2为0.9686,特性常数n为2.0446,其吸附过程可用Ho准二级反应动力学模型描述。     

离子液体改性沸石吸附水溶液中Cr(VI)的研究

利用离子液体十六烷基-3-甲基咪唑氯化物对天然沸石进行表面改性,并将改性沸石用于水中Cr(VI)的吸附,研究离子液体浓度、反应时间、p H等条件对Cr(VI)吸附性能的影响,采用X射线衍射和红外光谱对离子液体改性沸石进行表征。结果表明,咪唑离子浓度不大于0.3 mol/L的低浓度离子液体改性的沸石对Cr(VI)的吸附作用不明显,咪唑离子浓度大于0.9 mol/L的离子液体改性的沸石对Cr(VI)具有好的吸附效果;酸性条件有利于改性沸石对Cr(VI)的吸附;咪唑离子浓度为0.6、0.9 mol/L的离子液体改性的沸石吸附Cr(VI)平衡的时间分别为240、8 min。     

Reduction of Cr(VI) by hydrazine in solution saturated with KHCO3

Cr(VI) that exists in many industrial wastes is considered highly toxic. One of the most common ways to dispose of these wastes is to reduce Cr(VI) to Cr(III), which is less toxic and can be easily removed or fixed. Reduction of Cr(VI) by hydrazine in aqueous solutions saturated with potassium bicarbonate was studied in this paper. The content of Cr(VI), molar ratio of hydrazine to Cr(VI) and reaction temperature were 200-1000 ppm, 2:1-10:1 and 25-70 degrees C, respectively. Results showed that the overall reaction was third-order, i.e. first-order with respect to hydrazine and second-order with respect to Cr(VI). The apparent empirical activation energy was 75.6 kJmol(-1). The reaction kinetics could be interpreted by a three-step mechanism. Effect of the oxygen in the solution on the reduction of Cr(VI) was negligible.     

Optimization of the Simultaneous Determination of Cr(III) and Cr(VI) by Ion Chromatography with Chemiluminescence Detection

An optimized method for the simultaneous determination of Cr(III) and Cr(VI) in aqueous solutions using ion chromatography with chemiluminescence detection is described. Excellent resolution of the two chromium species was obtained using a single mixed-bed ion-exchange column with continuous elution. After postcolumn reduction of Cr(VI) to Cr(III), the light emitted during the Cr(III)-catalyzed oxidation of luminol with hydrogen peroxide was measured. Parameters affecting the postcolumn reactions such as reductant concentration, reductant mixing, point of luminol introduction, and luminol flow rate were optimized. The calibration curves in the range tested (0.01-50 μg L(-)(1)) were linear, and detection limits of 0.002 μg L(-)(1) for both Cr(III) and Cr(VI) were obtained. The results of the analyses of the water reference materials LGC CRM6010 and NIST SRM1643d with certified chromium values of 49 ± 4 and 18.53 ± 0.20 μg L(-)(1) and found to contain only Cr(III) were 49.2 ± 1.8 and 19.0 ± 1.5 μg L(-)(1), respectively. Values of 10.6 ± 0.5 and 10.1 ± 0.5 μg L(-)(1) were obtained when a simulated water sample containing 10 μg L(-)(1) Cr(III) and Cr(VI) was analyzed.     

Adsorption of Cr(VI) on 1,2-ethylenediamine-aminated macroporous polystyrene particles

An adsorbent, 1,2-ethylenediamine-aminated macroporous polystyrene (EDA-PSt) particles was used to adsorb Cr(VI) from aqueous solution. Effect of pH value, contact time, temperature, adsorbent dosage and initial Cr(VI) concentration on adsorption amount of Cr(VI) on EDA-PSt were investigated. The results showed that the adsorption isotherm can be well described by the Langmuir equation and the adsorption kinetics fitted to the pseudo-second-order model. According to Langmuir equation, Q_m was calculated to be 175.75 mg g⁻¹. The breakthrough curve experiment showed that the dynamic adsorption capacity for Cr(VI) on EDA-PSt was 100.06 mg g⁻¹. The adsorbed Cr(VI) could be desorbed by 0.1 mol L⁻¹ NaOH and the desorption ratio was 67.28%.     

Adsorption characteristics and separation of Cr(III) and Cr(VI) on hydrous titanium(IV) oxide

A hydrous titanium(IV) oxide was prepared to study the adsorption characteristics and the separation of chromium species. Batch sorption studies have been carried out to determine the effect of pH on the sorption of Cr(III) and Cr(VI) on hydrous TiO2. An excellent separation efficiency of Cr(III) and Cr(VI) was obtained at pH 2. The adsorption percentage of Cr(VI) was above 99%, whereas that of the Cr(III) was less than 1% at this pH. The adsorption isotherm of Cr(VI) on hydrous TiO2 at pH 2 was in good agreement with the Langmuir isotherm. The maximum adsorption capacity of Cr(VI) on TiO2 was 5 mg g(-1). The rate of adsorption of Cr(VI) by hydrous TiO2 with average particle diameter 250 and 500 microm has been studied under particle diffusion controlled conditions. The diffusion coefficients of Cr(VI) for both hydrous TiO2 having average particle diameter of 250 and 500 microm was calculated at pH 2 as 3.84 x 10(-10) m2 s(-1) and 8.86 x 10(-10) m2 s(-1), respectively.     

Adsorption of Cr(VI) from aqueous solution by hydrous zirconium oxide

A type of ZrO₂·nH₂O was synthesized and its Cr(VI) removal potential was investigated in this study. The kinetic study, adsorption isotherm, pH effect, thermodynamic study and desorption were examined in batch experiments. The kinetic process was described by a pseudo-second-order rate model very well. The Cr(VI) adsorption tended to increase with a decrease of pH. The adsorption data fitted well to the Langmuir model. The adsorption capacity increased from 61 to 66 mg g^?1 when the temperature was increased from 298 to 338 K. The positive values of both ΔH° and ΔS° suggest an endothermic reaction and increase in randomness at the solid–liquid interface during the adsorption. ΔG° values obtained were negative indicating a spontaneous adsorption process. The effective desorption of Cr(VI) on ZrO₂·nH₂O could be achieved using distilled water at pH 12.     

Adsorption of Cr(VI) using silica-based adsorbent prepared by radiation-induced grafting

Silica-based adsorbent was prepared by radiation-induced grafting of dimethylaminoethyl methacrylate (DMAEMA) onto the silanized silica followed by a protonation process. The FTIR spectra and XPS analysis proved that DMAEMA was grafted successfully onto the silica surface. The resultant adsorbent manifested a high ion exchange capacity (IEC) of ca. 1.30 mmol/g and the Cr(VI) adsorption behavior of the adsorbent was further investigated, revealing the recovery of Cr(VI) increased with the adsorbent feed and the equilibrium adsorption could be achieved within 40 min. The adsorption capacity, strongly depended on the pH of the solution, reached a maximum Cr(VI) uptake (ca. 68 mg/g) as the pH was in the range of 2.5–5.0. Furthermore, even in strong acidic (4.0 mol/L HNO₃) or alkaline media (pH 11.0), the adsorbent had a sound Cr(VI) uptake capacity (ca. 22 and 30 mg/g, respectively), and the adsorption followed Langmuir mode. The results indicated that this adsorbent, prepared via a convenient approach, is applicable for removing heavy-metal-ion pollutants (e.g. Cr(VI)) from waste waters.