Fabrication of Gd2O3/PSF Membranes via Aqueous Phase Inversion Method

This study aimed to investigate the effect of Gadolinium oxide (Gd2O3) concentration (0.5%, 1%, and 2%) on the performance of polysulfone (PSF) membrane. The membranes were fabricated by a common phase inversion method. The performance of membranes was determined based on pure water flux, bovine serum albumin (BSA) permeation test. These fabricated membranes were characterized by FTIR and contact angle measurements. The highest BSA rejection was 53%. The optimum membrane (2 % wt Gd2O3 /17 % wt PSF) in this study was determined by PSF 17% which successfully exhibited 53% rejection with filtrate flux for about 8.7 L/m2.h at a pressure of 10 bar

Some characteristics of fibre-reinforced semi-lightweight concrete with unexpanded perlite

Lightweight aggregate concrete is not a new invention of modern concrete technology, but dates back even to before the Christian era. Natural aggregates like scoria or pumice were utilised in masterpieces such as Babylon of the Sumerians, Hagia Sophia in Istanbul or the Pantheon of the Romans. The demand for lightweight aggregate concrete increased over time because of its advantages, specifically properties such as its thermal insulating properties and low density. It has also become an important structural material in off-shore construction during recent years. A comprehensive study was carried out in METU Mechanics of Materials Laboratory in order to investigate some characteristics of fibre-reinforced semi-lightweight concrete for seismic strengthening purposes of reinforced concrete framed structures. Semi-lightweight concrete containing unexpanded perlite, both as lightweight aggregate and as a supplementary cementing material, was reinforced by polypropylene and steel fibres, separately. Compressive strength, split tensile strength and modulus of elasticity measurements were carried out on cylinder specimens. Steel-mesh-reinforced semi-lightweight concrete plates were also tested as reference specimens for the toughness test and the results were compared with those for fibre-reinforced semi-lightweight concrete plates. Cylinder test results indicated a considerable increase in 28-day compressive strength in the case of unexpanded perlite powder replacement; while providing lower tensile strength and modulus of elasticity. Toughness test results indicated the superiority of polypropylene fibre-reinforced semi-lightweight concrete for seismic strengthening purposes in the case of fibre utilisatio

Removal of Pesticides from Wastewater by Membrane Proces

Purpose: The aim of this study was to investigate the removal performances of four pesticides (tributyl phosphate, flutriafol, dicofol and irgarol) by RO membranes. Methods: Three different RO membranes (BW30-LE, SW30-XLE and GE-AD) were used to reject pesticides in two transmembrane pressures of 10 and 20 bar in bench-scale membrane filtration cell. Tributyl phosphate and flutriafol were detected by GC/MS and dicofol and irgarol were monitored by HLPC instruments. Results: While the highest removal of tributyl phosphate was obtained by the BW30-LE and GE-AD membranes with 98-99%, all membranes (BW30-LE, SW30-XLE and GE-AD) rejected irgarol with around 98% performance at 10 and 20 bar pressures. Irgarol and dicofol removal performances of all the RO membranes tested were higher than 95%. Conclusion: Among the membranes tested, the BW30-LE membrane showed superior performance in the removal of all four pesticides, with removal efficiencies of 98-99%. Increasing TMP from 10 bar to 20 bar did not significantly affect pesticide removal efficiencies

Removal of pesticides from secondary treated urban wastewater by reverse osmosis

The residues of pesticides that reach water resources from agricultural activities in several ways contaminate drinking water resources and threaten aquatic life. This study aimed to investigate the performance of three reverse osmosis (RO) membranes (BW30-LE, SW30-XLE, and GE-AD) in rejecting four different pesticides (tributyl phosphate, flutriafol, dicofol, and irgarol) from secondary treated urban wastewater and also to elucidate the mechanisms underlying the rejection of these pesticides. RO experiments were conducted using pesticide-spiked wastewater samples under 10 and 20 bar transmembrane pressures (TMP) and membrane performances were evaluated. Overall, all the membranes tested exhibited over 95% rejection performances for all pesticides at both TMPs. The highest rejections for tributyl phosphate (99.0%) and irgarol (98.3%) were obtained with the BW30-LE membrane, while for flutriafol (99.9%) and dicofol (99.1%) with the GE-AD membrane. The increase in TMP from 10 to 20 bar did not significantly affect the rejections of all pesticides. The rejection performances of RO membranes were found to be governed by projection area as well as molecular weight and hydrophobicity/hydrophilicity of pesticides. Among the membranes tested, the SW30-XLE membrane was the most prone to fouling due to the higher roughness

Biological treatment and nanofiltration of denim textile wastewater for reuse

This study aims at coupling of activated sludge treatment with nanofiltration to improve denim textile wastewater quality to reuse criteria. In the activated sludge reactor, the COD removal efficiency was quite high as it was 91 +/- 2% and 84 +/- 4% on the basis of total and soluble feed COD, respectively. The color removal efficiency was 75 +/- 10%, and around 50-70% of removed color was adsorbed on biomass or precipitated within the reactor. The high conductivity of the wastewater, as high as 8 mS/cm, did not adversely affect system performance. Although biological treatment is quite efficient, the wastewater does not meet the reuse criteria. Hence, further treatment to improve treated water quality was investigated using nanofiltration. Dead-end microfiltration (MF) with 5 mu m pore size was applied to remove coarse particles before nanofiltration. The color rejection of nanofiltration was almost complete and permeate color was always lower than 10 Pt-Co. Similarly, quite high rejections were observed for COD (80-100%). Permeate conductivity was between 1.98 and 2.67 mS/cm (65% conductivity rejection). Wastewater fluxes were between 31 and 37 L/m(2)/h at 5.07 bars corresponding to around 45% flux declines compared to clean water fluxes. In conclusion, for denim textile wastewaters nanofiltration after biological treatment can be applied to meet reuse criteria

Recovery of caustic from mercerizing wastewaters of a denim textile mill

The objective of this study was to evaluate caustic recovery from mercerizing wastewater originating from a denim textile producing plant using membrane technology. For this purpose, ultrafiltration (UF) and nanofiltration (NF) processes were considered. In the first stage, in an attempt to control the possible membrane fouling, pretreatment alternatives of flocculation, centrifugation, and microfiltration were evaluated. These pretreatment application alternatives were unsuccessful as they did not provide considerable color and solids removal. In the second stage, UF and NF processes were tested using a tight UF membrane (GR95PP, Alfalaval) and three NF membranes (NP010 and NP030, Microdyn Nadir, and MPF34, Koch Membranes) to accomplish the caustic recovery without applying any pretreatment. The best performance was obtained with NP010 NF in terms of permeate flux along with color and COD rejections. Then, for this membrane the effects of transmembrane pressure (4.03 and 6.23 bar), cross-flow velocity (from 0.40 to 1.40 m/s), and feed temperature (20 and 40 degrees C) were investigated. Temperature positively affected the permeate flux without significant loss in recovery and rejections. Caustic stream produced had about 98-100% of NaOH in the feed at a concentration of 30-40 g/L and therefore was recyclable after a concentration process