Insights into nanofiltration of textile wastewaters for water reuse

Textile industry constitutes nowadays one the largest consumers of water, and consequently the wastewater reuse can be a profitable operation. In this study, the decontamination of pure dyes solutions (Remazol Turquoise Blue G, Remazol Yellow GR and Lanaset Blue 2R) and synthetic textile wastewaters was evaluated in a nanofiltration (NF) cross-flow cell, using polyamide NF membranes, NF90 and DK, with molecular weight cut-off between 200–400 Da and 150–300 Da, respectively. Permeate flux and the color reduction were evaluated for the different dye solutions under different temperature and pH conditions and, NaCl, wetting and dispersant concentrations. DK membrane showed the best results in terms of permeate flux for all the dye solutions tested. The highest permeate flux was achieved for higher temperatures under acidic to neutral pHs values, resulting in almost 100 % color removal for all situations.     

A membrane-based co-treatment strategy for the recovery of print- and beck-dyeing textile effluents

This paper describes the final part of a study on the recovery of print- and beck-dyeing wastewaters of the carpet manufacturing industry by membrane processes. These wastewaters had been previously treated separately where the print dyeing wastewaters were recovered by chemical precipitation followed by nanofiltration (NF) and beck-dyeing wastewaters were subjected to microfiltration (MF) and pH neutralization prior to NF. In this study, a co-treatment scheme after separate pre-treatment stages was adopted to simplify the overall process. The effect of mixing ratio on membrane fouling was also investigated. The co-treatment strategy was found advantageous since the number of NF units was minimized and the pH neutralization step in separate treatment of beck-dyeing wastewaters was eliminated, providing a reduction of chemical usage.     

Performance of gas chlorination in decolourization of textile dyeing wastewater: a pilot study

This study presents performance of gas chlorination in decolourization/degradation of textile dyeing wastewater, optimisation of operating parameters and process kinetics of gas chlorination since it eliminates the generation of hazardous sludge and economical treatment method. The pH, contact time and chlorine dosage were found optimised at 9, 30 min and 300 ppm, respectively. Colour (m^?1) of raw effluent was found in the range of 17–85, 14–52 and 15–24 and after the treatment, it was 3–7, 2–4 and 1–3 complying with the International colour standards at 436, 525 and 620 nm wavelengths, respectively. The percentage of colour removal and COD degradation were in the range of 89–95 and 28–45, respectively. Rate of reaction on colour removal and COD degradation were behaved in first order with kinetic rate constant ranged from 0.274 to 0.373 (min^?1) and 0.046 to 0.103 (min^?1), respectively. Performance of colour removal was achieved better than COD degradation.     

Pretreatment of nonbiodegradable landfill leachate by air stripping coupled with agitation as ammonia stripping and coagulation–flocculation processes

A combination process has developed as a pretreatment of non biodegradable leachate. The processes consist of air stripping coupled with agitation as a modified of ammonia stripping followed by coagulation–flocculation processes. The main aims of these processes are reducing a concentration of NH₃-N and organic matter as well as enhancing the biodegradability of landfill leachate. Ammonia stripped by the airflow rate of 10 L min^?1 at pH 11 for 3 h, while the agitation process applied to air stripping effluent for 2 h at the pH of 11.5 in 150 s^?1 gradient velocity. NH₃-N was removed at 96 % as removal ratio by the modified ammonia stripping in 5 h stripping time. Ferric sulfate, poly ferric sulfate and aluminum poly chloride was tested as a coagulant material in the coagulation process. Chemical oxygen demand (COD), suspended solids (SS), turbidity as well as the sludge ratios were discovered for each material operated under optimum condition of pH and dosage. The overall removal of NH₃-N, COD, biochemical oxygen demand, total organic carbon, and SS obtained by these processes were 96.5, 71.5, 56.5, 48.5, and 96.5 %, respectively, at the corresponding biodegradable ratio was modified from 0.20 to 0.31.     

Membrane filtration of chlorination and extraction stage bleach plant effluent in Indian paper Industry

The present study was carried out for the treatment of effluent from the chlorination and extraction stages of a bleach plant at an Indian pulp and paper mill. The effluents were taken from an integrated paper mill employing OCE_OPHH sequence for the bleaching of hardwood pulp. Effluent was treated via ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO). Thin film composite spiral-wound modules, having cross flow membranes composed of polysulfone and polyamide, were used in the study. Three initial inlet pressures were used for the UF and NF; 6.8, 10.3, and 13.7 bar. For RO initial inlet pressures of 10.3 bar, 13.7 bar and 17.2 bar, were taken in different trials. The retentate from each experiment was recycled back to the feed and retreated until the inlet pressure increased to the maximum cut-of pressure for each membrane. The UF permeate was fed to the NF, which was subsequently fed to the RO. Variations in the trans-membrane pressure and permeate flux were assessed. The removal of pollutants and fouling indices were obtained for each membrane at each initial inlet pressure.     

Effect of aluminum on microstructural evolution during hot deformation of TX32 magnesium alloy

The effect of Al (0.4 and 1 wt%) addition on the hot deformation behavior of the Mg–3Sn–2Ca (TX32) alloy has been studied with the help of processing maps generated in the temperature and strain rate ranges of 300–500 °C and 0.0003–10 s^?1. The deformed specimens have been examined as regards changes in texture and microstructure using electron back scatter diffraction and transmission electron microscopy, respectively. The map for the TX32 base alloy exhibited two dynamic recrystallization (DRX) domains in the temperature and strain rate ranges: (1) 300–350 °C and 0.0003–0.001 s^?1, and (2) 390–500 °C and 0.005–0.6 s^?1. While 0.4 wt% Al addition to TX32 did not result in any significant change in the processing map, the map for the alloy with 1 wt% Al (TX32-1Al) exhibited four domains in the ranges: (1) 300–325 °C and 0.0003–0.001 s^?1, (2) 325–430 °C and 0.001–0.04 s^?1, (3) 430–500 °C and 0.01–0.5 s^?1, and (4) 430–500 °C and 0.0003–0.002 s^?1. In the first three domains, DRX has occurred, whereas in the fourth domain, grain boundary sliding takes place causing intercrystalline cracking in tension. In Domain 1 for all the alloys, DRX has occurred predominantly by basal slip and recovery by climb as confirmed by the resulting basal texture and tilt type sub-boundary structure. In Domain 2 of the base alloy and Domain 3 of the alloy with 1 wt% Al, second-order pyramidal slip dominates associated with cross-slip which randomizes the texture, and forms tangled dislocations and twist type sub-boundaries in the microstructure. The addition of 1 wt% Al causes solid solution strengthening and results in Domain 2 of the map of TX32-1Al alloy and in this domain basal+prismatic slip dominate.     

Synthesis of Fe/ZnO composite nanocatalyst and its sonophotocatalytic activity on acid yellow 23 dye and real textile effluent

Nanocatalysts such as ZnO, Fe and Fe/ZnO composite were synthesized for better treatment of dye than the conventional treatment methods. The catalysts were characterized using SEM, EDAX, BET surface area, XRD and DRS. The degradation of acid yellow 23 dye in aqueous solution has been investigated using sonolysis, photolysis and sonophotocatalysis. The effect of different conventional operating parameters such as initial solution pH, gas purging (Argon, Oxygen, Air and Nitrogen) and H₂O₂ addition, under sonolysis (13 and 25 mm probe tip diameter) and photolysis (UV light), showed a maximum of 41 % colour removal for 0.0187 mmol/L dye solution under photolysis with 88.2 mmol/L H₂O₂ addition. Among the catalysts used, 98 % dye colour removal was obtained with 0.2 g/L Fe/ZnO composite under 60 min of sonophotolysis that had been benefitted by the synergistic effects. The HPLC spectrum of the untreated dye and treated dye supports the claim of eradication of the parent dye compound. Sonophotocatalytic treatment of real textile effluent in the presence of 6 g/L Fe/ZnO composite and 264.6 mmol/L H₂O₂ reduced the COD level from 792 to 174.4 mg/L in 240 min to meet the allowable effluent discharge standard into running water streams. The studied treatment methods were found to be effective for the degradation of acid yellow 23 dye and subsequently in real textile effluent too.     

The Hot Workability of SiCp/2024 Al Composite by Stir Casting

The hot workability of SiC_p/2024 Al composite was explored by conducting hot compression simulation experiments on Gleeble-3500 under temperatures of 300–500 °C and strain rates of 10^?3–1 s^?1. Constitutive equation was developed through hyperbolic sine function, and the activation energy was calculated to be 151 kJ mol^?1. The hot processing maps referring to dynamic material model were drawn in a true strain range from ?0.2 to ?0.8. At the strain of ?0.8, the recommended regions in processing map contained two domains: superplastic domain (500 °C, 10^?3 s^?1) with an efficiency of about 0.72 and DRX domain (500°C, 1 s^?1) with an efficiency of about 0.45. Together with macrostructure and microstructure observations, it was suggested to remove the DRX region.     

Processing Map of AZ31-1Ca-1.5 vol.% Nano-Alumina Composite for Hot Working

A processing map for extruded AZ31-1Ca-1.5NAl composite has been developed, which exhibited four important domains for hot working. The corresponding temperatures and strain rates associated with these domains are: (1) 250–350°C and 0.0003–0.01 s^?1; (1A) 350–410°C and 0.0003–0.01 s^?1; (2): 410–490°C and 0.002–0.2 s^?1; and (3) 325–410°C and 0.6 s^?1 to 10 s^?1. Dynamic recrystallization (DRX) occurred in all the four domains although different slip mechanisms and recovery processes are involved. Basal slip and prismatic slip dominates deformation in Domains 1 and 1A, respectively, with recovery occurring by climb that is lattice self-diffusion controlled. However, because of the high strain rates in Domain 3, recovery occurs through a climb process, controlled by grain boundary self-diffusion. The recovery mechanism in Domain 2 is cross-slip assisted by pyramidal slip along with basal and prismatic slip. The grain size has a linear relation with Zener–Hollomon parameter in all the domains. At high strain rates, the composite undergoes shear fracture at lower temperatures and intercrystalline fracture at higher temperatures. All of the identified DRX domains are suitable for conducting bulk metal forming processes although the one with the highest strain rates (Domain 3) is preferred for achieving high productivity.     

Hot workability analysis with processing map and texture characteristics of as-cast TX32 magnesium alloy

Hot deformation behavior of as-cast TX32 (Mg–3Sn–2Ca) alloy has been studied in uniaxial compression in the temperature and strain rate ranges of 300–500 °C and 0.0003–10 s^?1 with a view to characterize the evolution of microstructure and texture. On the basis of the temperature and strain rate dependence of flow stress, a processing map has been developed and the crystallographic orientation information on the deformed specimens has been obtained from electron back scatter diffraction micro-texture analysis. The processing map revealed two domains of dynamic recrystallization in the temperature and strain rate ranges of (1) 300–350 °C and 0.0003–0.001 s^?1 and (2) 390–500 °C and 0.005–0.6 s^?1. Specimens deformed at peak in Domain 1 exhibited maximum intensity of basal poles located at about 35–45° to the compression axis while those deformed at peak in Domain 2 showed near-random texture. Schmid factor analysis of different slip systems operating in the two domains suggests that basal + prismatic slip causes the basal texture in Domain 1 while second-order pyramidal slip randomizes the texture in Domain 2.     

pH dependent poly[2-(methacryloyloxyethyl)trimetylammonium chloride-co-methacrylic acid]hydrogels for enhanced targeted delivery of 5-fluorouracil in colon cancer cells

Stimuli responsive hydrogels have shown enormous potential as a carrier for targeted drug delivery. In this study we have developed novel pH responsive hydrogels for the delivery of 5-fluorouracil (5-FU) in order to alleviate its antitumor activity while reducing its toxicity. We used 2-(methacryloyloxyethyl) trimetylammonium chloride a positively charged monomer and methacrylic acid for fabricating the pH responsive hydrogels. The released 5-FU from all except hydrogel (GEL-5) remained biologically active against human colon cancer cell lines [HT29 (IC₅₀ = 110–190 μg ml^?1) and HCT116 (IC₅₀ = 210–390 μg ml^?1)] but not human skin fibroblast cells [BJ (CRL2522); IC₅₀ ≥ 1000 μg ml^?1]. This implies that the copolymer hydrogels (1–4) were able to release 5-FU effectively to colon cancer cells but not normal human skin fibroblast cells. This is probably due to the shorter doubling time that results in reduced pH in colon cancer cells when compared to fibroblast cells. These pH sensitive hydrogels showed well defined cell apoptosis in HCT116 cells through series of events such as chromatin condensation, membrane blebbing, and formation of apoptotic bodies. No cell killing was observed in the case of blank hydrogels. The results showed the potential of these stimuli responsive polymer hydrogels as a carrier for colon cancer delivery.     

Treatment of palm oil mill effluent (POME) by coagulation flocculation process using peanut–okra and wheat germ–okra

Coagulation–flocculation has been proven as one of the effective processes in treating palm oil mill effluent (POME), which is a highly polluted wastewater generated from palm oil milling process. Two pairs of natural coagulant–flocculant were studied and evaluated: peanut–okra and wheat germ–okra. This research aims to optimize the operating parameters of the coagulation flocculation process in removing turbidity, total suspended solid and chemical oxygen demand (COD) from POME by using a central composite design in the Design Expert^® software. Important parameters such as operating pH, coagulant and flocculant dosages were empirically determined using jar test experiment and optimized using response surface methodology module. Significant quadratic polynomial models were obtained via regression analyses (R²) for peanut–okra (0.9355, 0.9534 and 0.8586 for turbidity, total suspended solids and COD removal, respectively) and wheat germ–okra (0.9638, 0.9578 and 0.7691 for turbidity, total suspended solids and COD removal, respectively). The highest observed removal efficiencies of turbidity, total suspended solids and COD (92.5, 86.6 and 34.8%, respectively, for peanut–okra; 86.6, 87.5 and 43.6%, respectively, for wheat germ–okra) were obtained at optimum pH, coagulant and flocculant dosages (pH 11.6, 1000.1 mg/L and 135.5 mg/L, respectively, for peanut–okra; pH 12, 1170.5 mg/L and 100 mg/L, respectively, for wheat germ–okra). The coagulation flocculation performance of peanut–okra and wheat germ–okra were comparable to each other. Characterizations of the natural coagulant–flocculant, as well as the sludge produced, were performed using Fourier transform infrared, energy-dispersive X-ray spectroscopy and field emission scanning electron microscope. More than 98% of water was removed from POME sludge by using centrifuge and drying methods, indicating that a significant reduction in sludge volume was achieved.     

AFM analysis of the surface of nanoporous membranes: application to the nanofiltration of potassium clavulanate

This study presents the structural characterization of the surface of four commercial nanofiltration membranes: NF90 (polyamide) and NF (polypiperazine amide) from Filmtec^TM and NP010 and NP030 (polysulfone) from Microdyn Nadir^®, by Atomic Force Microscopy (AFM). These membranes have been studied before and after undergoing a filtration process with potassium clavulanate. The fast Fourier filtering of AFM images with very high magnification (40 × 40 nm) has allowed identifying the pore size distribution and geometry of the pores on the surface of the membrane before their use. Images between 0.5 × 0.5 and 10 × 10 μm² have allowed the study of the surface roughness of the samples before and after being used to filtrate potassium clavulanate solutions. The results of roughness and power spectral fractal dimension along with the skewness and kurtosis of the height distribution have been analyzed in terms of pore size, hydraulic permeability, and the adsorption of clavulanate for the different samples.     

Performance of anaerobic–anoxic–aerobic batch fed moving-bed reactor at varying phenol feed concentrations and hydraulic retention time

A simulated wastewater containing phenol (1,000–2,500 mg/L), thiocyanate (SCN^?) of 800 mg/L, COD (4,200–8,150 mg/L), and ammonia–nitrogen (NH₄ ⁺–N) of 500 mg/L was treated in a sequential anaerobic (B1)–anoxic (B2)–aerobic (B3) batch fed moving-bed reactor (MBR) system. Total hydraulic retention time (HRT) was varied from 5 to 10 days with B1 2.5 to 5 days; B2 and B3: 1.25–2.5 days each. In B1, 25–63 % of phenol and 23–53 % of COD removals were achieved and feed phenol above 1,500 mg/L, inhibited COD and phenol removals in B1. In B2, more than 90 % phenol removal was achieved along with COD removal and denitrification. In B2, with increase in phenol loading, though phenol and COD removal rates increased, SCN^? removal rate decreased above phenol loading of 0.28 g/L day. In B3, NH₄ ⁺–N removal efficiency decreased above loading of 0.24 g NH₄ ⁺–N/L day. The overall efficiency of the fed batch MBR system was independent of feed phenol concentration up to 2,500 mg/L at constant total HRT of 6 days. NH₄ ⁺–N removal efficiency deteriorated significantly, when total HRT of fed batch MBR was less than 6 days. Modified Stover–Kincannon model showed the best fit for removal of substrates in three reactors and Haldane’s inhibition model predicted NH₄ ⁺–N removal in B3.     

An integrated approach for enhanced textile dye degradation by pre-treatment combined biodegradation

The wastewater released by the textile industries affects aquatic, plant and human life. Though there are many conventional wastewater treatment techniques, interest on coupled treatment methods has increased in the recent times owing to their increased efficiency. In the present study, the textile wastewater was pre-treated by three different techniques, viz. sonication, photocatalysis and ozonation. Increasing the treatment time increased the biological oxygen demand to chemical oxygen demand (BOD/COD) ratio, and thus the biodegradability was about 0.6–0.73. Effluent pre-treated by photocatalysis showed relatively higher biodegradability compared to ozonation and sonication. The degradation of aromatic compounds due to pre-treatment was substantiated by Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (¹H NMR) spectroscopy. Since pre-treatment increased the biodegradability of the effluents, further biological degradation using acclimatized sludge biomass resulted in COD removal efficiencies 94, 91 and 82 %, respectively, for photocatalysis, sonication and ozonation. The morphology of the organisms which played a major role during the degradation of pre-treated effluent was examined under scanning electron microscope (SEM).     

Anisotropy of acousto–optic figure of merit in lithium tetraborate crystals

We analyse anisotropy of acousto–optic figure of merit (AOFM) for Li₂B₄O₇ crystals in order to estimate the prospects of these crystals in acousto–optics. We find that the maximal AOFM, 3.44 × 10^?15 s³/kg, is peculiar for the isotropic acousto–optic interaction of the incident ordinary optical wave with the quasi-longitudinal acoustic wave. For the case of anisotropic diffraction in Li₂B₄O₇, the maximum 1.87 × 10^?15 s³/kg can be reached using the interaction of the extraordinary optical wave with the quasi-longitudinal acoustic wave. The case of collinear diffraction is characterized by small AOFMs, with the largest value 0.26 × 10^?15 s³/kg.     

Adsorbents made from textile scraps: preparation,characterization and application for removal of reactive dye

Textile scraps from the clothing industry were used to prepare a low-cost adsorbent to remove anionic dye from textile effluents. Adsorbents were prepared through pyrolysis and chemical activation with K₂CO₃. These samples were characterized through thermogravimetric analysis, scanning electron microscopy, N₂ adsorption/desorption isotherms, Fourier transform infrared spectroscopy, point of zero charge, isoelectric point, elemental composition and proximate analysis. Batch kinetic experiments and adsorption isotherm modeling were conducted in different conditions. The surface properties of the adsorbents were significantly influenced by the activation process. The highest BET surface area (S_BET = 358.55 m² g^?1) was attributed to the sample with chemical treatment. The results indicate that activation process raised 700% the adsorption capacity. The adsorption was strongly dependent on the pH. For the activated adsorbent, 6 g L^?1 was sufficient for the complete removal of 40 mg L^?1 Reactive Black 5 (RB5) solution. The monolayer capacity was up to 10.3 mg g^?1 and was higher than a commercial activated carbon commonly used in textile sector, which was 9.7 mg g^?1.     

Compression stress–strain and creep properties of the 52In–48Sn and 97In–3Ag low-temperature Pb-free solders

Lead (Pb)-free, low melting temperature solders are required for step-soldering processes used to assemble micro-electrical mechanical system (MEMS) and optoelectronic (OE) devices. Stress–strain and creep studies, which provide solder mechanical properties for unified creep-plasticity (UCP) predictive models, were performed on the Pb-free 97In–3Ag (wt.%) and 58In–42Sn solders and counterpart Pb-bearing 80In–15Pb–5Ag and 70In–15Sn–9.6Pb–5.4Cd alloys. Stress–strain tests were performed at 4.4 × 10^?5 s^?1 and 8.8 × 10^?4 s^?1. Stress–strain and creep tests were performed at ?25, 25, 75, and 100°C or 125°C. The samples were evaluated in the as-fabricated and post-annealed conditions. The In–Ag solder had yield stress values of 0.5–8.5 MPa. The values of ΔH for steady-state creep were 99 ± 14 kJ/mol and 46 ± 11 kJ/mol, indicating that bulk diffusion controlled creep in the as-fabricated samples (former) and fast-diffusion controlled creep in the annealed samples (latter). The In–Sn yield stresses were 1.0–22 MPa and were not dependent on an annealed condition. The steady-state creep ΔH values were 55 ± 11 kJ/mol and 48 ± 13 kJ/mol for the as-fabricated and annealed samples, respectively, indicating the fast-diffusion controlled creep for the two conditions. The UCP constitutive models were derived for the In–Ag solder in the as-fabricated and annealed conditions.     

Microstructural investigation of AA 2195 T81 chips formed during a metal-cutting process

In this study, the microstructure of AA 2195 T81 metal-cutting chips formed during a turning operation were characterized using microscopy and diffraction techniques. At a constant strain of 2, the resulting strain rate imposed on the metal was varied from 0.8 × 10⁴ to 2.6 × 10⁵ s^?1. At strain rate of 0.8 × 10⁴ s^?1, the resulting microstructure contained regions of 100 nm ultrafine grains. At the highest strain rate of 2.6 × 10⁵ s^?1, 150–200 nm ultrafine grains were observed plus overaged precipitates. The grain size increment and appearance of overaged precipitates with the higher strain rate is conjectured to be a result of temperature increment and not of direct strain rate.     

Decolourisation of Direct Orange S dye by ultra sonication using iron oxide nanoparticles

Biosynthesised iron oxide nanoparticles (INPs) less than 100 nm were used to decolourise the textile dye, Direct Orange S by the process of ultra sonication. The parameters tested for the decolourisation of the Direct Orange S dye were the INP concentration (0.2–1g/l), pH (3–11) and H₂O₂ concentration (2–8 ml/l). The rate of decolourisation process was performed by both stirrer and ultra sonicator method using the first-order kinetics ln(c/c₀). The percentage of dye removal for the optimum conditions such as INP, 1g/l (87.2%); pH, 9 (85.5%) and H₂O₂ concentration 8 ml/l (86.5%) were observed. The Direct Orange S dye was degraded efficiently by sonolysis (60 min) than by the magnetic stirrer method (120 min). High-performance liquid chromatography results showed that the peak for Direct Orange S dye was not present when the dye sample was treated by either H₂O₂ + INP or INP alone. Use of biosynthesised iron NPs in Direct Orange S dye (azo dye) decolourisation by a simple non-toxic Fenton reaction is a safe and novel approach. Industrialisation of this technique will be an economical way to decolorise the textile dyes present in water systems.