Separation of Cyanide Ions by Foam Fractionation

Abstract

The technique of adsorption of cyanide ions on foam bubbles was studied as an alternative to chemical oxidation which is practiced in cyanide waste treatment. The technique of foam fractionation was previously applied to the removal of heavy metals and proved to be successful. The free cyanide ions and complex species both responded positively to the formation of a separate foam phase. The results obtained so far show that satisfactory separation of cyanide compounds is possible if certain parameters are properly selected. There are other factors which have not been investigated before, and they seem to have a major role in the performance of this operation.     

泡沫分离除去水溶液中微量金属离子

以十二烷基苯磺酸为表面活性物质,采用泡沫分离技术分别对脱除水溶液中微量的铁、铜、钠离子的分离过程进行了研究.重点考察了溶液的pH、表观气速、表面活性剂浓度及泡沫塔装液量对分离效果的影响.结果表明在各自最佳操作条件下铁离子(Ⅲ)的去除率为95.2%,富集比为13.6;铜离子(Ⅱ)的去除率为94.6%,富集比为16.5;钠离子去除率为73.1%,富集比为32.3.与常规的表面活性剂十二烷基硫酸钠相比,十二烷基苯磺酸在泡沫分离过程结束后不会在体系中引入新的金属离子,这为探索脱盐新方法提供了依据.     

Foam Fractionation Rates

Abstract

An empirical model enables the relation of the batch foam fractionation rate as a power function of the air rate and of the instantaneous residual surfactant concentration, eliminating the bubble size which is difficult to control and to measure. For the cationic surfactant, ethylhexadecyl-dimethylarnmonium bromide, the batch foam fractionation rate is directly proportional to the residual surfactant concentration to the first power, except for dilute (>45 mg/liter) solutions, and including suspensions containing colloidal ferric oxide and polynucleated, complexed cyanider Constants obtained from batch data can be used in the analogue equation for continuous operation to predict accurately the continuous foam fractionation rate, for a single air rate but over a substantial range of feed rates and feed surfactant concentrations. Continuous data from an entirely different column can be fit by a power function equation of the same form, with the power on the effluent or bottoms surfactant concentration again being unity. The accuracy of the predictive equations is in the range 10–18%.     

Models for Interactions between Ionic Surfactants and Nonsurface-Active Ions in Foam Fractionation Processes

Abstract

Interactions are analyzed between an ionic surfactant and nonsurface-active ions (colligends) of opposite charge being separated in foam fractionations. Surfactant selectivity for competing colligends is determined in terms of models based on surfactant—colligend ion pair formation in the feed solution to a foam fractionation unit, based on colligend-surfactant counterion exchange at the gas-solution, bubble interfaces, and based on surface exchange coupled with ion pair formation in the bulk solution. Accurate, continuous-flow, single-equilibrium-stage foam fractionation data for NO^? ₃, BrO^? ₃, CIO^? ₃, and I^?, each versus Br^?, the counterion of the ethylhexadecyldimethylammonium cation, are used to discriminate among the models. Based on a detailed statistical analysis of the selectivity coefficients determined by two interaction models for each of the four colligends, the hypothesis of colligend-counterion exchange at the gas-solution interface is shown to be valid and that of solution ion pair formation is not substantiated. The surface exchange model provides selectivity coefficients which are quite constant over a tenfold concentration range and yet which are very sensitive to data inaccuracies.     

Foam Fractionation and Drainage

Abstract

The effect of drainage on the lesser accumulation ratio R in foam is calculated. If time t ₀ alloted to drainage is varied, In R - 1) is expected to be, in simplest instances, proportional to t ₀. The expansion factor 1/φ of the foam, when this reaches the receptacle, depends on t ₀ but the product (R - 1)φ ought to be independent of t ₀ These conclusions are not contradicted by the meager published data.     

The Continuous Foam Fractionation of Phenol

Abstract

The continuous foam fractionation of phenol using a quaternary ammonium salt, ethylhexadecyldimethylammonium bromide, has been investigated. Experiments were conducted to determine the effects of pH and percentage reflux on the phenol removal. It was found that approximately 80% removal of phenol was obtained at a pH of 11.9 with 70% reflux. Poor removal occurred in the slightly basic region of 8.0 to 10.0; while adequate removal was obtained with no pH adjustment. Maximum removal occurred at 70 to 80% reflux. Sodium hydroxide was used to adjust the pH in most cases. Although similar effects were found using ammonium hydroxide, the percent removal of phenol was, in general, lower.     

Fractionation of Nanocellulose by Foam Filter

The foam fractionation method was applied for nanocellulose. Experiments were carried out with enzymatically pretreated nano-fibrillated cellulose (NFC) from softwood, as well as commercial products. Narrow channels (plateaus) between bubbles prevent the flow of coarse particles along the water, so that foam acts like a filter. The advantage of the method is no risk of clogging, which could be a big problem for conventional filters or screens. Mean particle size (effective size by means of dynamic light scattering measurement) was reduced by foam fractionation, and the reduction range depended on the cellulose grade and the type of surfactant. The yield turned out to be low, probably because of particle aggregation due to the interaction with surfactant.     

泡沫分离方法回收钪

采用十二烷基聚氧乙烯琥珀酸单酯磺酸钠和十二烷基硫酸钠混合物作为表面活性剂，间歇式泡沫分离回收水溶液中的钪。讨论了料液pH值、表面活性剂浓度、鼓泡气流率、离子强度和操作时间等对分离效果的影响，得到了适宜的工艺条件。     

糖-蛋白质混合体系泡沫分离过程研究

利用环流泡沫分离技术对若干糖 -蛋白质 (牛血清白蛋白 )混合模拟体系进行了分离实验 ,研究了 p H值对溶液表面张力和分离效果的影响 ,在综合考虑蛋白质泡沫夹带量、去除率、糖的损失率及分离因子的基础上 ,得到了泡沫分离的最优 p H值。研究结果表明 ,采用环流泡沫分离技术可以实现糖与蛋白质的分离 ,是生物多糖与蛋白质初级分离的一种有效方法     

泡沫分离技术及其发展现状

探讨了泡沫分离技术的原理、泡沫分离设备及泡沫分离技术的研究进展。泡沫分离过程的性能受很多因素的影响 ,例如 ,进料液浓度、气泡尺寸、气体流量、泡沫的排液、进料位置、聚并、温度等。阐述了现有的几种新技术 ,如低重力条件操作、通过压力梯度而提高分离效率。此外 ,还简要介绍了泡沫分离塔中传质单元数和传质单元高度的概念。     

Surfactant Recovery from Water Using Foam Fractionation

Abstract

The purpose of this study was to investigate the use of foam fractionation to recover surfactant from water. A simple continuous mode foam fractionation was used and three surfactants were studied (two anionic and one cationic). The effects of air flow rate, foam height, liquid height, liquid feed surfactant concentration, and sparger porosity were studied. This technique was shown to be effective in either surfactant recovery or the reduction of surfactant concentration in water to acceptable levels. As an example of the effectiveness of this technique, the cetylpyridinium chloride concentration in water can be reduced by 90% in one stage with a liquid residence time of 375 minutes. The surfactant concentration in the collapsed foam is 21.5 times the feed concentration. This cationic surfactant was easier to remove from water by foam fractionation than the anionic surfactants studied.     

Concentration Effects on Separation Selectivity in Foam Fractionation

Abstract

Removal of cadmium, copper, and nickel ions from aqueous solution by foam fractionation has been studied using a chelating surfactant, 4-dodecyl-diethylenetriamine. The rate of removal is a function of concentration of both metallic ions and surfactant. In the low concentration range for the metallic ions compared to that of the surfactant, the order of removal was found to be Cd²⁺ > Ni²⁺ > Cu²⁺. However, at higher concentrations of ions, the order becomes inverse, Cu²⁺ > Ni²⁺ > Cd²⁺. A selectivity coefficient for the separation of a specified ion from one or more ions using a chelating surfactant is shown to be dependent on the surface tension of the complex and the chelation constants. The relationship between separation selectivity of the removal of the metallic ions and concentration of both surfactant and metallic ions is discussed     

消泡剂共存体系中泡沫分离蛋白质

在以牛血清白蛋白(BSA)为目标蛋白、聚环氧丙烷环氧乙烷甘油醚(PGE)为消泡剂的模拟体系中,考察了表面活性剂种类(非离子型Tween-20和离子型SDBS)、浓度、溶液pH及操作参数(气体流量、初始液池高度)对BSA分离效率的影响. 结果表明,2种活性剂均能改善模拟体系的泡沫性能,使泡沫分离. 后者作用更强并能促进BSA的吸附,因DBS-通过静电作用与带相反电荷的BSA结合形成疏水性更强的BSA-DBS复合物. pH通过影响BSA的电荷分布而影响其与SDBS的结合,进而影响对BSA的吸附,初始BSA浓度0.1 g/L, PGE 4 mg/L, SDBS 50 mg/L, pH为3.4时,约66%蛋白质浓缩在泡沫液中,富集比为5.34. 增加气速或初始液池高度可得到较高收率,但富集比减小.     

Foam Fractionation of Mercury(ll) Nitro Complexes

Abstract

Using a recycle foam separation apparatus, the foam fractionation distribution factor, γ/C, of the anionic metal nitro complexes of mercury(II) with the cationic surfactant, hexadecyltrimethylammonium bromide, was determined. The distribution factor was measured as a function of nitric acid concentration. The maximum occurred at 0.1 N nitric acid, which is in agreement with the anionic ion-exchange column distribution coefficient. Total reflux foam fractionation experiments yielded a 150-fold increase in the enrichment factor with a 20% recovery of the mercury(II) ion.     

泡沫分离过程中泡沫层总高度对持液率的影响

以乳链菌肽发酵液为模拟体系,研究了泡沫分离过程中泡沫层总高度对泡沫塔出口持液率εout以及泡沫层轴向持液率分布特性的影响.实验发现:在泡沫层形成过程中,εout从一个较低值逐渐升高到一个较高的稳定值;泡沫在塔内泡沫相中的停留时间不是εout的决定性因素,气速对εout的影响很大.同时还发现:随着泡沫层总高度的增加,εout缓慢下降而泡沫层与液层界面处的持液率急剧上升,可以推测出整个轴向持液率特性分布会上移.实验数据表明仅仅用静态泡沫的排液时间代替上升动态泡沫的停留时间的方法来预测εout的一般方法可能得出错误的结果.     

Continuous Foam Fractionation of Phosphate by a Cationic Surfactant

Abstract

Continuous foam fractionation experiments in one equilibrium stage were performed using ethylhexadecyldimethylammonium bromide and potassium dihydrogen phosphate. The pH of the solution was maintained at 5.4 at which only H₂PO₄- was present. The effects of surfactant and phosphate concentrations and liquid and gas flow rates on the percent stripping of phosphate and the distribution factor of phosphate were studied. Equilibria between surface and bulk liquid phases were found to be adequate to explain the inverse relationship between the distribution factor of phosphate and the phosphate and surfactant concentrations.

For optimum separation of phosphate, defined as percent stripping, [100(c_f — cw)/cf], low liquid and high gas flow rates must be used with dilute solutions of both surfactant and phosphate. Further, multiple equilibrium stages should be employed.     

泡沫分离法分离桔梗皂苷的工艺研究

采用间歇式泡沫分离法对桔梗提取液中的桔梗皂苷予以分离工艺条件研究;实验以富集比、回收率以及带液率为指标衡量分离效果,在单因素试验基础上,通过正交试验法,获得桔梗皂苷的最佳分离条件。结果表明分离桔梗皂苷的最佳工艺条件为:进料浓度0.014 mg/m L,气体流速700 m L/min,温度30℃,表面活性剂用量(0.505 mg/m L)30 m L,回收率为77.58%,富集比为2.50,带液率为21.67%。因此泡沫分离桔梗皂苷是一种简单、有效、可行的分离方法。     

Separation of Tea Saponin by Two-Stage Continuous Foam Fractionation

A technology of two-stage continuous foam fractionation for tea saponin recovery was studied for increasing both the enrichment ratio and the recovery percentage. In the first stage, the effect of air flow rate, the initial pH, the feed flow rate, and the feed position were studied at a temperature of 60°C. The results showed that when the conditions of the first stage were at a temperature of 60°C, air flow rate 150 mL/min, pH 5.3, feed flow rate 1.92 mL/min, and feed position at the interface between the liquid phase and the foam phase, the enrichment ratio, and the recovery percentage of tea saponin were 4.02 and 56.4%, respectively, and the effluent solution was added to the second stage as the initial solution. When the conditions of the second stage were at a temperature of 30°C and an air flow rate of 300 mL/min, the recovery percentage of tea saponin reached 47.6%, and the foamate was added to the first stage as feed solution. The total recovery percentage of tea saponin reached 86.3% by the two-stage continuous foam fractionation.     

Foam Fractionation of Protein with the Presence of Antifoam Agent

Foam fractionation is a promising technology for protein concentration or purification. However, the presence of an antifoam agent in fermentation broth restricted direct application of the technology. A preliminary approach of the surfactant-assisted foam process was conducted with a simulated system consisting of targeted protein bovine serum albumin (BSA), and a mixed antifoam agent (AF520, silicon oil/PGE mixture). The effects of all three classes of surfactants (anionic SDBS, cationic CTAB, and non-ionic Tween-20) on BSA foam fractionation were examined respectively. Also, the influences of solution pH, PGE, BSA, and NaCl were taken into account. The results revealed that all three classes of surfactants could stabilize foam film, so that the foam process could be operated, while the ionic surfactant exhibited excellent performance on condition that it was allowed to firmly interact with BSA to form a more hydrophobic complex, especially for cationic CTAB. When solution pH was adjusted to 7.5 and CTAB was 20 mg · mL^?1, 90% of BSA could be extracted from a previous non-foaming system containing 100 mg · mL^?1 BSA and 4 mg · mL^?1 AFA, and the enrichment reached 7.42. A higher enrichment of BSA could be obtained with increasing addition of AFA but at the expense of the recovery. On the contrary, increasing BSA concentration gave rise to an opposite performance. The experiments also showed that the foam stability of the system was substantially enhanced by NaCl, significantly lowering the enrichment.     

Rates of Continuous Foam Fractionation of Dilute Kraft Black Liquor

Abstract

Dilute solutions of black liquor obtained from the kraft pulping of Pinus radiata have been subject to continuous foam separation in laboratory-scale equipment. A power function relationship between the foam fractionation rate and both the air rate and the effluent or bottoms concentration has been established which is similar to that previously developed for binary solutions of pure surfactants.