Removal of metal ions by ultrafiltration of a micellar solution containing anionic surfactant

Heavy metals in wastewater were removed by ultrafiltration of a micellar solution containing surfactant such as sodium dodecyl sulfate. Experimental results showed that permeate flux was primarily controlled by the operating parameters such as transmembrane pressure difference, flow rate and feed concentration. The average permeate flux increased at a higher transmembrane pressure, feed velocity, and at a lower solution concentration. The transmembrane pressure had a relatively small effect on metal removal whereas the level of surfactant-to-metal ratio (S/M) had a substantial effect. The optimal ratio of S/M for a best removal of metal ions was measured around 5 and 8 in the presence of sodium dodecyl sulfate, and the affinity resulted in the order of Cr> Co> Ni> Mg.     

丙烯酰胺-丙烯酸-丙烯羟肟酸共聚物乳液脱除电镀废水中的重金属离子

采用反相乳液聚合法合成了丙烯酰胺(AM)-丙烯酸(AA)- 丙烯羟肟酸(AHA)共聚物乳液。考察了该共聚物配方中丙烯羟肟酸用量、共聚物乳液的投量和pH值对电镀废水中重金属离子的脱除效果。结果表明：pH=10,丙烯羟肟酸在共聚物乳液中的用量≥15%,共聚物乳液的投量为20～30 mg/L时,脱除电镀废水中重金属离子的效果最好,Cr、Cu、Ni和Zn等重金属离子的脱去率≥99.5%,处理后的水中每种重金属离子浓度≤0.2 mg/L。     

Removal of metal ions by water‐soluble polymacromonomers in conjunction with ultrafiltration membrane

The macromonomer polyethylene glycol methylether methacrylate was homo‐ and copolymerized with 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid under three feed monomer ratios. The initiator used was ammonium peroxydisulfate (0.2 mol %). All the polymers were completely soluble in water. The copolymer composition was determined by elemental analysis. The metal ion interaction capability of the three polymers was investigated through the liquid‐phase polymer‐based retention (LPR) technique at different values of pH and filtration factor Z. The highest metal ion retention ability was observed at pH 5.0. The homopolymer showed a high selectivity for Ni(II) ions at pH 3.0. The copolymers (PEGMEM)_1.51‐co‐(APSA)_1.00 and (PEGMEM)_1.00‐co‐(APSA)_1.95 showed a high selectivity for Cr(III) ions at pH 3.0. The maximum retention capacity, in general, was similar for the homo‐ and copolymers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2955–2960, 2004     

Removal of lead ions from wastewater using novel Schiff-base functionalized solid-phase adsorbent

ABSTRACT

This article discusses the synthesis, characterization and lead ions sorption capability of a novel recyclable Schiff-base anchored cross-linked polyacrylamide. The synthesized polymeric adsorbent was characterized by FT-IR technique, XRD and SEM analysis. Sorption parameters, such as solution’s pH, contact time, polymer dose, lead ions initial concentration, etc., were studied and optimized. Experimentally, the optimum sorption pH was around 5.0 and the sorption equilibrium was attained after 30 min. Under the optimal conditions, the maximum sorption capacity was found to be 355 mg/g, which is considered high when compared with different adsorbents. Effect of interfering ions on the sorption capacity was explored. Sorption isotherms, kinetic and thermodynamic studies were considered to identify the sorption behavior of the new polymeric adsorbent. Sorption isotherm studies showed that the maximum sorption capacity was attended as a result of homogeneous monolayer sorption of lead ions on the surface of the synthesized polymeric adsorbent. The mechanism of lead ions sorption by the synthesized polymeric adsorbent was found to be chemisorption complexation mechanism. Moreover, kinetic studies revealed that the sorption process followed a pseudo second order kinetic model. Thermodynamic data depicted that the sorption process is spontaneous, reversible and exothermic in nature. Experiments on elution and reusability of the synthesized polymeric adsorbent were executed and the results showed its validity for reuse for at least four cycles with 11% loss in its original capacity. Finally, the applicability of the synthesized Schiff-base anchored solid phase adsorbent for the removal of lead ions from industrial wastewater was explored and the results indicated its good removal efficiency.     

Removal of Ni(II) ions from wastewater by micellar enhanced ultrafiltration using mixed surfactants

Ni(II) ions were removed from aqueous waste using micellar enhanced ultrafiltration (MEUF) with a mixture of surfactants. The surfactant mixture was the nonionic surfactant Tween 80 (TW80) mixed with the anionic surfactant sodium dodecyl sulfate (SDS) in different molar ratios ranging from 0.1–1.5. The operational variables of the MEUF process such as pH, applied pressure, surfactant to metal ion ratio and nonionic to ionic surfactant molar ratio (α) were evaluated. Rejection of Ni and TW80 was 99% and 98% respectively whereas that for SDS was 65%. The flux and all resistances (fouling resistance, resistance due to concentration polarization) were measured and calculated for entire range of α respectively. A calculated flux was found to be declined with time, which was mainly attributed to concentration polarization rather than resistance from membrane fouling.     

Removal of methylene blue from aqueous solution by a carbon-microsilica composite adsorbent

Microsilica, one kind of industrial solid waste material, was utilized firstly to prepare a carbon-microsilica composite adsorbent (CMS). The prepared adsorbent was characterized with XPS, SEM and Gas sorption experiments. The results indicated the SO₃H groups, which are very effective in capturing cationic organic dye, were introduced onto the surface of CMS; the Brunauer-Emmett-Teller (BET) surface area (S _BET ) and total pore volume (V _total ) of CMS reach 51m²/g and 0.045 cm³/g, respectively. Meanwhile, the possibility of the utilization of the adsorbent for removal of methylene blue (MB) from aqueous solution was investigated. The effect of pH, contact time and initial MB concentration for MB removal were studied. Equilibrium data were modeled using the Langmuir, Freundlich and Dubinin-Radushkevich equations to describe the equilibrium isotherms. It was found that data fit to the Langmuir equation better than the Freundlich equation. Maximum monolayer adsorption capacity was calculated at different temperatures (298, 308, and 318 K) reach 251.81, 283.76 and 309.70 mg/g, respectively. It was observed that adsorption kinetics obeys the pseudo-first-order equation.     

Removal of Fe(III) ions from dilute aqueous solutions by alginic acid‐enhanced ultrafiltration

The removal of Fe(III) ions from aqueous solutions was studied using membrane filtration. A water‐soluble polymer alginic acid (AA) was used to bind the metal ions, which was followed by batch ultrafiltration using poly(methyl methacrylate‐methacrylic acid) membranes modified with poly(ethylene glycol) (PMMA‐MA‐PEG). The complexation behavior of AA and the effect pH on the rejection of iron were investigated. Maximum recovery of 87.13% was obtained when the filtration was carried out in the presence of AA at pH 3.1. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1096–1101, 2000     

采用超滤膜回收氯醋树脂离心母液

为了减少氯乙烯-醋酸乙烯树脂在聚合生产过程中废水的排放,采用中空纤维超滤膜浓缩分离离心母液和漂洗水。通过对膜装置运行过程的研究,确定了采用全时气水混合进料的方式运行效果最为良好,透过液可回用于生产,节约成本;浓缩液为随母液流失的树脂,回到生产线脱水干燥,提高产品产率。该方法大大降低了废水的排放量,减轻了污水处理系统的负荷。     

Removal of copper ions by a cation-exchange resin in a semifluidized bed

The removal of copper ions was studied experimentally in a semifluidized bed charged with a strong cation-exchange resin, Amberlite 200C. The semifluidized bed system was formed by inserting a retaining grid in a packed bed and increasing the fluid velocity above U_mf. In this arrangement, the bed is separated into two sections; the upper packed bed section and the lower fluidized bed section. As the fluid velocity increases, the portion of the packed bed section becomes larger. As expected, the breakthrough curve obtained from the semifluidized bed lies between those from packed and fluidized beds. The breakthrough curves of copper ions were predicted reasonably well by using an axial dispersion model. In this paper, the effects of the liquid flowrate and the retaining grid height on the breakthrough behavior are extensively discussed.     

Stimulation of the passivation of iron by tungstate,molybdate and chromate ions

The effects of tungstate, molybdate and chromate ions on the passivation of iron were investigated, and these oxyanions stimulated the passivation especially at lower pH.The results were rationalized by the dissolution-precipitation mechanism of iron passivation.In order to bring about the passivity of iron, it was required that iron first dissolves into solution, and then a ferric hydroxide or a ferric complex with oxyanion should be produced on the metal surface, which was followed by the dyhydration or the condensation reaction of these compounds to form ferric oxide.     

Removal of zinc ions in wastewater by electrodialysis

To obtain useful data for treatment of the wastewater discharged from zinc electroplating processes, we investigated the effects of operating parameters, such as the initial concentration of dilute solution, the flow velocity and the applied voltage, on removal rate of Zn²⁺ in the model solutions using an electrodialysis system. Zinc ions in the solutions were effectively removed by the electrodialyzer with CMX cation exchange membranes and AMX anion exchange membranes. The initial concentration of dilute solution, the flow velocity and the applied voltage strongly affected the performance of the electrodialysis system. As the initial concentration of dilute solution, the flow velocity and the applied voltage were increased, the removal ratio was increased. The energy consumption was increased as the initial concentration of dilute solution and the applied voltage were increased, whereas the effect of the flow velocity on the energy consumption was negligible.     

Removal of cadmium from wastewater by enhanced ultrafiltration using surfactants

In order to recover cadmium ion from wastewater, a process based on enhanced ultrafiltration was finalised. The originality of the solution here proposed lies on the coupled use of ceramic membranes and of a surfactant added to the water to be treated. This paper deals with the study of the influence of experimental conditions upon permeation flux and selectivity of the separation. The process is efficient and flexible since a single stage treatment allows to reduce the concentration of cadmium in the effluent by a factor of about 750; this high performance in selectivity is on a par with high fluxes of permeate (roughly 170 L.h.^?1.m^?2 at 25°C and 3 × 10⁵ Pa).     

Preparation of polysulfone-based block copolymer ultrafiltration membranes by selective swelling and sacrificing nanofillers

Selective swelling of block copolymers of polysulfone-b-poly(ethylene glycol) is an emerging strategy to prepare new types of polysulfone ultrafiltration membranes. Herein, we prepared nanoporous polysulfone-b-poly(ethylene glycol) ultrafiltration membranes by selective swelling and further promoted their porosity and ultrafiltration performances by using CaCO₃ nanoparticles as the sacrificial nanofillers. Different contents of CaCO₃ nanoparticles were doped into the solution of polysulfone-b-poly(ethylene glycol), and thus obtained suspensions were used to prepare both self-supported and bi-layered composite structures. Selective swelling was performed on the obtained block copolymer structures in the solvent pair of ethanol/acetone, producing nanoporous membranes with poly(ethylene glycol) lined along pore walls. The CaCO₃ nanoparticles dispersed in polysulfone-b-poly(ethylene glycol) were subsequently etched away by hydrochloric acid and the spaces initially occupied by CaCO₃ provided extra pores to the block copolymer layers. The porosity of the membranes was increased with increasing CaCO₃ content up to 41%, but further increase in the CaCO₃ content led to partial collapse of the membrane. The sacrificial CaCO₃ particles provided extra pores and enhanced the connectivity between adjacent pores. Consequently, the membranes prepared under optimized conditions exhibited up to 80% increase in water permeance with slight decrease in rejection compared to neat membranes without the use of sacrificial CaCO₃ particles.     

Metal cation removal by P(VC-r-AA) copolymer ultrafiltration membranes

A series of amphiphilic copolymers containing poly(vinyl chloride-r-acrylic acid) (P(VC-r-AA) ) was synthesized and used to prepare membranes via a nonsolvent induced phase separation method. The prepared membranes were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, and water contact angle and zeta potential measurements. The copolymer P(VC-r-AA) chains did not dissolved in a coagulation bath, indicating that the AA segments were completely retained within the membrane. Enriching degree of AA segments in surface layer was 2 for copolymer membrane. In addition, the introduction of AA segments made the membrane electronegative and hydrophilic so that the membrane was sensitive to the solution pH. The fouling resistance, adsorption of Cu(II), Cr(III) and Ce(IV) ions and the desorption properties of the membranes were also determined. The copolymer membranes exhibited good antifouling performance with a fouling reversibility of 92%. The membranes also had good adsorption capacities for Cu(II), Cr(III) and Ce(IV) ions. The optimal pH for Cu(II) adsorption was 6 and the copolymer membrane has potential applications for low concentration Cu(II) removal.

Open image in new window

     

Removal of textile dyes from aqueous solutions by natural phosphate as a new adsorbent

The objective of this study was to investigate the ability of natural phosphate (NP) to remove textile dyes from aqueous solutions. The adsorption of methylene blue (MB) as a reference molecule for the adsorption studies of organic molecules, basic yellow 28 (BY 28) and reactive yellow 125 (RY 125) representatives of two families of textile dyes was studied in a batch mode. The experimental results show that NP can totally remove MB and BY 28, whereas a low adsorption affinity was found in the case of RY 125. The adsorption rate data were analysed using the pseudo-first order kinetics of Lagergren and the pseudo second order model to determine adsorption rate constants. The isotherms of adsorption data were analyzed by various adsorption isotherm models. The adsorption was temperature- and pH-dependent with a high adsorption capacity of MB and BY 28 in the basic range and a high adsorption of RY125 in an acidic range.     

Removal of mercury from natural gas by a new activated adsorbent from olive stones

This study was devoted to the valorization of a plant waste (olive stones): that is widely available in Mediterranean countries in order to remove mercury from natural gas. The raw material from olive stones was prepared by pyrolysis, chemical activation with phosphoric acid, and physical activation under steam. Two olive stone‐based granular activated carbons were prepared: one with the virgin stones, while the other was impregnated with sulphur. After treatment, the adsorbents obtained were characterized by determining the iodine number, the methylene blue index, and by estimating the porous properties by N₂ adsorption at 77 K. Thermogravimetric analysis and infrared spectroscopy analysis were carried out to determine the functional groups before and after mercury adsorption. An experimental study of vapour‐phase mercury adsorption by the activated carbons (virgin and sulphur‐impregnated) and a comparison with a commercial material (HGR) were performed. The comparison, made by analyzing the adsorption in a continuous mode, showed that the proportion of sulphur and the porosity were important for the removal of mercury. In the conditions used, the mercury adsorption on the ACs studied follows a physisorption mechanism. The results showed that granular activated carbon‐based olive stones (sulphur‐impregnated) are very efficient to remove mercury (with 2864 μg/g) and also less expensive than commercial activated carbon due to their local availability.     

Adsorption behavior of fluoride ions using a titanium hydroxide-derived adsorbent

The removal behavior of fluoride ions was examined in aqueous sodium fluoride solutions using a titanium hydroxide-derived adsorbent. The adsorbent was prepared from titanium oxysulfate (TiOSO₄·xH₂O) solution, and was characterized by X-ray diffraction, scanning electron microscopy, thermogravimetry-differential thermal analysis, Fourier transform infrared spectrum and specific surface area. Batchwise adsorption test of prepared adsorbent was carried out in aqueous sodium fluoride solutions and real wastewater containing fluoride ion. The absorbent was the amorphous material, which had different morphology to the raw material, titanium oxysulfate, and the specific surface area of the adsorbent (96.8 m²/g) was 200 times higher than that of raw material (0.5 m²/g). Adsorption of fluoride on the adsorbent was saturated within 30 min in the solution with 200 mg/L of fluoride ions, together with increasing pH of the solution, due to ion exchange between fluoride ions in the solution and hydroxide ions in the adsorbent. Fluoride ions were adsorbed even in at a low fluoride concentration of 5 mg/L; and were selectively adsorbed in the solution containing a high concentration of chloride, nitrate and sulfate ions. The adsorbent can remove fluoride below permitted level (< 0.8 mg/L) from real wastewaters containing various substances. The maximum adsorption of fluoride on the adsorbent could be obtained in the solution at about pH 3. After fluoride adsorption, fluoride ions were easily desorbed using a high pH solution, completely regenerating for further removal process at acidic pH. The capacity for fluoride ion adsorption was almost unchanged three times after repeat adsorption and desorption. The equilibrium adsorption capacity of the adsorbent used for fluoride ion at pH 3 was measured, extrapolated using Langmuir and Freundlich isotherm models, and experimental data are found to fit Freundlich than Langmuir. The prepared adsorbent is expected to be a new inorganic ion exchanger for the removal and recovery of fluoride ions from wastewater.     

Effect of Zr ions on the structure and optical properties of lithium borosilicate molybdate glass system

The glass system with the composition [(20-x) MoO₃– x ZrO₂–15 SiO₂– 65 Li₂B₄O₇, x = 0, 1, 2, 3, 4, and 5 mol %] was successfully synthesized using the melt quenching method. The XRD results of this glassy system confirmed the glassy nature of the prepared glasses. The density of this glassy system presented higher values while the molar volume provided lower values with increasing ZrO₂ content. The FTIR result showed that the spectrum of each sample consisted of broad bands that de-convoluted into several peaks. These peaks were characterized and the structure of each sample was recognized. Additionally, the optical measurements showed that sample x = 0 mol% provided a sharp ultra-violet cut-off at 380 nm, while the other samples showed a transition peak in the (210–230) nm range. The energy of optical band gaps of these glass samples decreased and the Urbach energy increased by increasing ZrO₂ content. Moreover, the different optical parameters of these glass samples were calculated and showed that the studied glasses could be considered promising materials to be used in different optical applications such as nonlinearity and optoelectronics.     

复合功能树脂NXD-2对水中邻苯二甲酸单丁酯的去除性能

酞酸单酯是水体环境中一类新型的环境激素污染物。以含叔胺基的复合功能树脂NXD-2为吸附剂,以邻苯二甲酸单丁酯（MBP）为目标污染物,通过吸附等温线、热力学、动力学和柱吸附脱附实验,考察了NXD-2对MBP的吸附性能。研究结果表明,NXD-2对MBP的吸附以氢键作用为主,在288～313 K的温度范围内,平衡吸附量随温度的升高而升高;升高温度有利于加快NXD-2对MBP的去除速率。柱吸附脱附研究表明,在进水浓度为300 mg·L^-1的高浓度条件下,吸附出水的前100 BV中,溶液中MBP的浓度低于检测限（10 mg·L^-1）,说明NXD-2对MBP具有较高的处理深度;同时NXD-2具有较好的脱附效果,脱附体积达到20 BV时,脱附率接近100%。因此,复合功能树脂NXD-2作为一种吸附剂,在水体中酞酸单酯的去除方面具有良好的应用前景。