Separation of oil from oily wastewater using low cost ceramic membrane

Safe disposal of oily wastewater is a global issue across the industrial world. Stable oil-in-water emulsion has been separated by dead end filtration using low cost ceramic membrane. The efficiency of separation at different oil-water emulsion concentrations was evaluated at different trans-membrane pressures. Maximum rejection of oil 95.4% was observed for membrane sintered at 850 °C for oil concentration of 250 mg/L at 137.89 kPa. The permeate oil concentration was within the permissible range of environmental tolerance (<12 mg/L). The flux decline data was compared with various pore blocking models and it was appraised that cake filtration model best represents the fouling mechanism within the experimental range of pressure and oil-in-water concentration. Solvent permeation studies revealed that nonpolar solvents were more permeable than the polar solvents. The selection parameter of 14.78×10^?6m³/m²·s indicates a good combination of flux permeation, declination and rejection for the membrane sintered at 900 °C.     

Preparation of microfiltration membrane supports using coarse alumina grains coated by nano TiO2 as raw materials

To increase the mixing uniformity of coarse alumina grains with a small amount of nano TiO₂ particles, TiO₂ particles were prepared on the surface of coarse Al₂O₃ grains by in-situ hydrolysis of TiCl₄. The coated coarse Al₂O₃ powder was used to prepare microfiltration membranes supports. The effects of TiO₂ content and sintering temperatures on the bending strength, porosity and pore size distribution of the obtained supports were studied. The results show that the melted nano TiO₂ grains locate mainly at the neck of Al₂O₃ grains, which increases the bending strength of the support by increases the neck area. However, the bending strength is weakened if the TiO₂ content is excessive. No aggregated nano TiO₂ grainsare found. The resulting supports sintered at 1650 °C for 2 h yields a bending strength of 55.4 MPa, a porosity of 38% with a mean pore size of 8.0 μm.     

High-porosity mullite ceramic foams prepared by selective laser sintering using fly ash hollow spheres as raw materials

A novel method to prepare high-porosity mullite ceramic foams by selective laser sintering (SLS) using fly ash hollow spheres (FAHSs) as raw materials was reported. The complex-shaped FAHS green bodies and ceramic foams without delamination or cracks were prepared by SLS. The influence of sintering temperatures on linear shrinkage, phase composition, porosity and mechanical properties was investigated. With the increase of sintering temperature from 1250?°C to 1400?°C, the compressive strength of ceramic foams increased from 0.2?MPa to 6.7?MPa causing the fracture mechanism change from fracturing along FAHSs to across FAHSs, while the porosity of ceramic foams decreased from 88.7% to 79.9% which was higher than those of ceramic foams prepared by the conventional methods. The relatively high porosity of ceramic foams was resulted from the inner hollow structure of FAHSs, the interspaces between stacking FAHSs, and the gaps between FAHSs directly related to SLS. The results above indicated that the fabrication of high-porosity FAHS ceramic foams by SLS could achieve the advanced utilization of FAHS solid waste.     

Synthesis of manganese ferrite from non-standard raw materials using ceramic technique

Manganese ferrite spinel has been synthesized by using mill scale and fines of manganese ore sinter as sources of iron oxide and manganese oxide, respectively. The magnetic and physico-mechanical properties of the produced sample are largely dependent not only on the sintering condition but also on the Mn:Fe mole ratio. The effect of silica (which is one of the constituents of the fines of manganese ore sinter) on the properties of the sintered samples is investigated. The results show that a single phase of manganese ferrite spinel with weak magnetic properties is obtained in a sample containing a Mn:Fe mole ratio of 1.4:2 and sintered at 1300 °C for 2 h. On the other hand, a maximum saturation magnetization (62 emu/g) with reasonable physico-mechanical properties is obtained for a sample containing a Mn:Fe mole ratio of 1.3:2 and sintered at the same sintering conditions.     

大块液膜技术处理含六价铬废水

以磷酸三丁酯(TBP)为载体,煤油为稀释剂,NaOH为反萃剂,采用大块液膜技术处理含95~100mg/LCr(VI)的模拟废水。考察了液膜相用量、载体体积分数及反萃剂浓度对大块液膜过程中Cr(VI)传质过程的影响。结果表明,大块液膜技术对废水中Cr(VI)的去除效果较好。Cr(VI)迁移速率随TBP体积分数的提高而加快。当反萃剂NaOH浓度大于0.5mol/L时,反萃剂浓度对Cr(VI)传质过程的影响较小。处理后废水中Cr(VI)含量降至0.5mg/L以下,达到国家排放标准。     

Removal of chromium (VI) from aqueous solutions using quaternized chitosan microspheres

In this study, quaternized chitosan microspheres (QCMS) were prepared and its Cr(VI) removal potential was investigated. Batch experiments were conducted to examine kinetics, adsorption isotherm, pH effect, and thermodynamic parameters. Equilibrium was attained within 50 min and maximum removal of 97.34% was achieved under the optimum conditions at pH 5. Adsorption data for Cr (VI) uptake by the QCMS were analyzed according to Langmuir, Freundlich, and Temkin adsorption models. The maximum uptake of Cr(VI) was 39.1 mg·g^-1. Thermodynamic parameters for the adsorption system were determinated at 293 K, 303 K, 313 K and 323 K. (ΔH°=16.08 kJ·mol^-1;ΔG°=-5.84 to -8.08 kJ·mol^-1 and ΔS°=74.81 J·K^-1·mol^-1). So 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 obtainedwere negative indicating a spontaneous adsorption process. The kinetic process was described by a pseudo-second-order rate equation very well. The results of the present study indicated that the QCMS could be considered as a potential adsorbent for Cr (VI) in aqueous solutions.     

Removal of chromium(VI) from aqueous solutions using polypyrrole-based magnetic composites

PPy/Fe₃O₄/AgCl composites were prepared via in situ polymerization for the removal of highly toxic Cr(VI). The structure and morphology of the prepared composites were characterized by the XRD, SEM, TEM, and VSM examinations. Up to 100 % removal was found with 1000 mg/L Cr(VI) aqueous solution at pH 2.0. The process of Cr(VI) ions’ adsorption was easy to reach equilibrium at higher temperatures. Adsorption results showed that Cr(VI) removal efficiency by the composites decreased with an increase in pH. Adsorption kinetics was described by the pseudo-second-order rate model. Isotherm data fitted well to the Langmuir isotherm model. Desorption experiment showed that the regenerated adsorption of PPy/Fe₃O₄/AgCl can be reused successfully for three times successive adsorption–desorption cycles without appreciable loss of its original capacity.     

Fabrication of low cost,green silica based ceramic hollow fibre membrane prepared from waste rice husk for water filtration application

In order to develop low cost ceramic membranes and effectively utilize abundantly and dumped waste agriculture, fabrication of green silica based ceramic hollow fibre membranes from waste rice husk was evaluated. Rice husk was converted into amorphous and crystalline silica based rice husk ash (ARHA and CRHA) by burning process at 600?°C and 1000?°C, respectively. The properties of silica based rice husk ashes were studied by transmission electron microscopy (TEM), x-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), BET analysis, thermogravimetry and differential thermal analysis (TG/DTA) and x-ray fluorescence (XRF). Effect of silica content and sintering temperature towards membrane fabrication were investigated and characterized in term of morphological properties, mechanical strength, surface roughness, pore size distribution, porosity and pure water flux (PWF). The ceramic hollow fibre membrane (CHFM) prepared at 37.5?wt% CRHA content and sintered at 1200?°C achieved a good mechanical strength (71.2?MPa) and excellent porosity (50.2%). As a result, high PWF with value ~ 300?L/m² h and stable at 20?min was obtained. Due to the excellent pure water flux, the prepared ceramic membrane from waste rice husk hold promise for water treatment application.     

Fabrications and applications of low cost ceramic membrane from kaolin: A comprehensive review

The application of low cost ceramic membrane from kaolin has attracted much interest due to its excellent mechanical stability, chemical and thermal resistivity and most importantly, because it is cost effective, in some cases, compared to polymeric membranes. The advantage of kaolin based ceramic membrane is its thermal properties that allow sintering at much lower temperature than alumina. Although many studies have been made on the application of kaolin based ceramic membranes, detailed discussions were scarcely made and the information on the fabrication of ceramic membrane from kaolin is very limited. This article is aimed to make a comprehensive review on ceramic membrane from kaolin for its fabrication methods and applications. An attempt is also made to show the future direction of the R and D on the kaolin based ceramic membrane.     

Development of a low cost micro-porous ceramic membrane from kaolin and Alumina,using the lignite as porogen agent

The manufacturing of low cost ceramic flat and tubular membranes via dry pressing and extrusion, using low cost material, namely, natural kaolin, Alumina, and lignite as a pore forming agent was the purpose in this study. These membranes are designed to be used as a support for multilayer ceramic membranes.This study includes the preparation and the characterization of the different membranes.The selected composition was 20% of lignite, 15% of Alumina and 65% of Kaolin, the membranes have been obtained at 1200 °C as a sintering temperature. The membranes show good behavior for both configurations, with a porosity above 36% and a mechanical strength of 39 MPa or the tubular membranes and 34% for the flat ones.     

Artificial neural network (ANN) approach for modeling of Cr(VI) adsorption from aqueous solution by zeolite prepared from raw fly ash (ZFA)

In this present work, artificial neural networks (ANN) are applied for prediction of percentage adsorption efficiency for the removal of Cr(VI) ions from aqueous solution by zeolite (ZFA) prepared from raw fly ash (RFA). The off operational parameters such as initial pH, adsorbent dosage, contact time and temperature is studied to optimize the conditions for maximum removal of Cr(VI) ions. Three equations, i.e. Morris–Weber, Lagergren, and pseudo second order have been tested to track the kinetics of removal process. The Langmuir, Freundlich, Redlich–Peterson, Temkin, and D-R are subjected to sorption data to estimate sorption capacity. Thermodynamic parameters showed that the adsorption of Cr(VI) onto ZFA was feasible, spontaneous and endothermic. Artificial neural networks are effective in modeling and simulation of highly non-liner multivariable relationships. The comparison of the removal efficiencies of Cr(VI) using ANN model and experimental results showed that ANN model can estimate the behavior of the Cr(VI) removal process under different conditions.     

Uptake of Cr (VI) by Sphingomonas paucimobilis Biomass from Aqueous Solutions

The Sphingomonas paucimobilis biomass has been successfully utilized to degrade several persistent organic pollutants (POPs). However, few studies have been conducted to use it to remove heavy metals from aqueous solutions. In the present study, biosorption experiments for Cr (VI) were investigated using nonliving biomass of S. paucimobilis isolated from activated sludge, Lianyungang Dapu sewage treatment plant, China. The effects of several parameters including solution pH, contact time, and ionic strength, etc. on Cr (VI) uptake were studied. The biomass was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS) and Fourier transform infrared spectrometer (FTIR). The applicability of the Langmuir and Freundlich models was tested. The correlation coefficients (R) of both models were greater than 0.95. The maximum adsorption capacities were found to be 28.5 mg/g for Cr (VI) at 20°C. The adsorption process was quick and found to follow the pseudo-second-order equation. The optimum adsorption was achieved at pH 2. The adsorption was also NaCl concentrations dependent.     

Kinetic,isotherm, and thermodynamic studies of Cr(VI) removal from aqueous solution using mesoporous silica materials prepared by fly ash

A series of mesoporous silica materials (FMD, FMT, and FMC were synthesized with DTAB, TTAB, and CTAB as template, respectively) have been prepared using fly ash as a silica resource. The as-synthesized materials were characterized by BET, XRF, FTIR, and XPS. The results confirmed the mesoporous structure and nitrogen content to act as potential adsorbents. The adsorption properties of these materials were also investigated by batch adsorption experiments. The FMC exhibited the highest effective removal of Cr(VI) (99%). The Cr(VI) adsorption process over FMC follows the pseudo-second-order kinetic and Langmuir model. Thermodynamic studies revealed that the Cr(VI) adsorption by FMC was spontaneous and endothermic. The study of the adsorption mechanism showed that the removal of Cr (VI) by FMC is through electrostatic attraction and chemical reduction. The coexisting ions experiment showed that FMC had high selectivity for Cr(VI). After three regeneration cycles, the Cr(VI) removal rate of FMC adsorbent still remained about 80%. Thus, this inexpensive adsorbent (FMC) is suitable for removing Cr(VI) from discharged industrial water.     

Sorption rules of chromium(VI) ions by wood-based polyampholytes

The sorption laws of chromium(VI) on highly porous wood ionites in dependence on the pH of the medium, the metal ion concentration in the solution, and the duration of the phase contact have been investigated. It was found that the magnitude of the exchange capacity of the sorbents is defined by the ion state of the functional groups of polyamfolytes and chromate ions in the solution.     

催化动力学光度法测定废水中痕量铬(VI)

在pH值为4.0的缓冲溶液中,磷酸和棉红在100℃下反应生成天蓝色物质(λmax=675nm),该物质在微量铬(VI)的催化下被溴酸钾氧化褪色,建立了测定痕量铬(VI)的催化动力学新方法,方法的检出限是0.76ng·mL-1,线性范围0～0.06μg·mL-1,用于测定电镀废水中铬(VI),结果令人满意。     

Removal of chromium (VI) from aqueous solutions using poly(4‐vinyl pyridine) beads

Sorption of hexavalent chromium ions from aqueous solution by poly 4‐vinyl pyridine [Poly(4‐VP)] was studied. The batch method was applied for adsorption processes. The effects of initial ion concentration, time, pH and temperature on adsorption were investigated. A treatment time of 60 min was found to be sufficient to reach equilibrium. pH 3.0 was found as the optimum pH value for the process. The maximum adsorption performance was achieved at 86.7 mg g^?1 using 500 mg L^?1 Cr (VI) solutions. The process of adsorption of Cr (VI) was explained by Langmuir isotherm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2865–2870, 2006     

Transport of chromium(VI) through a Cyanex 921‐supported liquid membrane from HCl solutions

The transport of chromium(VI) through a flat‐sheet supported liquid membrane containing Cyanex 921 as a carrier has been investigated. The permeation of the metal is investigated as a function of various experimental variables: hydrodynamic conditions, concentration of chromium(VI) and HCl in the feed phase, carrier concentration and diluent in the membrane and strippant concentration in the stripping phase. The mass transfer coefficient and the thickness of the aqueous boundary layer were calculated from the experimental data. Furthermore, the selectivity of Cyanex 921‐based flat‐sheet supported liquid membrane towards different metal ions and the behaviour of the system against other carriers are presented. Copyright © 2003 Society of Chemical Industry     

Enhanced adsorption behavior of U(VI) using PZSC/ZnO ceramic composite derived from polyphosphazene

In this study, a new type of ceramic composite (PZSC/ZnO) was successfully synthesized using N, P, and S co-doped carbon microspheres derived from polyphosphazene with zinc oxide. The morphology and structure were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive spectroscopy, Raman, X-ray diffraction, BET, and thermogravimetric. Batch experiments were used to explore the adsorption performance under different pH values, initial concentrations, contact times, and temperatures. The results showed that the maximum adsorption capacity of the PZSC/ZnO ceramic composite for uranium was 470.5 mg/g (pH = 5.5, t = 40 min, and T = 25°C). The adsorption process followed the nonlinear Langmuir model and the pseudo-second-order kinetic model, demonstrating that the monolayered combination of U(VI) with the PZSC/ZnO ceramic composite and the adsorption mechanism was chemical adsorption. Thermodynamic data revealed that the adsorption was a spontaneous endothermic process. Furthermore, P and N may be involved in the adsorption of uranyl ions through binding to the O atoms from ZnO. The main forces between U(VI) and the PZSC/ZnO ceramic composite were attributed to ZnO and heteroatoms doped in the material.     

Characterization of microstructural and thermal properties of steatite/cordierite ceramics prepared by using natural raw materials

Steatite/cordierite ceramics were fabricated by using a combined method of high-energy ball milling, cold pressing and sintering. Steatite and cordierite powders were separately synthesized from natural raw materials such as kaolinite and talc. The powder blends containing different amounts of cordierite (5, 10 and 20 wt.%) were wet-milled for 1 h in a vibratory ball-mill (Fritsch™ Pulverisette 7 Premium Line), using zirconia vial and balls. After drying, powders were compacted to cylindrical preforms with a diameter of 12.7 mm by uniaxial pressing at 300 MPa. The green compacts were sintered at 1200-1350 °C for 2 h under air. Phase, microstructural and thermal characterizations of the sintered materials were carried out by using X-ray diffraction technique (XRD), thermogravimetry/differential thermal analyzer (TG/DTA) and scanning electron microscope (SEM). Densities, open porosity and water absorption values of sintered bodies were measured by Archimedes method. Thermal expansion coefficient (CTE) measurements were conducted by a dilatometer.     

Study of sorption of chromium(VI) ions by fibre anion-exchangers

Sorption of chromium(VI) ions by fibre anion-exchangers containing pyridine, imidazole, hydrazidine, and aliphatic amino groups was investigated. It was shown that the basicity of the sorbents has almost no effect on their selectivity in absorption of chromium ions from solutions. The fibres with pyridine and imidazole groups have higher distribution coefficients, and their capacity for chromium ions is 130 and 120 mg/g, respectively. Sorption of chromium(VI) ions by the fibre sorbent with pyridine groups also corresponds to a mixed diffusion mechanism in dynamic conditions and the internal diffusion coefficient is 3.10 ⁻¹⁰ cm²/sec. Fibres with low-basicity pyridine groups are resistant to the oxidizing effect of chromium(VI) ions and their exchange capacity is preserved in repeated sorption-desorption cycles. Conversion of pyridine groups to the form of a strong base decreases the chemical stability of the sorbent in absorption of chromium(VI) ions from solutions. Translated from Khimicheskie Volokna, No. 2, pp. 55–57, March–April, 1997.