Carmen Gutiérrez-Bouzán

Valorization of waste obtained from oil extraction in moringa oleifera seeds: coagulation of reactive dyes in textile effluents

Moringa oleifera seeds contain about 40% of highly valued oil due to its wide range of applications, from nutritional issues to cosmetics or biodiesel production. The extraction of Moringa oil generates a waste (65%–75% of seeds weight) which contains a water soluble protein able to be used either in drinking water clarification or wastewater treatment. In this paper, the waste of Moringa oleifera extraction was used as coagulant to remove five reactive dyes from synthetic textile effluents. This waste constitutes a natural coagulant which was demonstrated to be effective for the treatment of industrial reactive dyestuff effluents, characterized by alkaline pH, high NaCl content and hydrolyzed dyes. The coagulation yield increased at high NaCl concentration, whereas the pH did not show any significant effect on dye removal. Moringa oleifera showed better results for dye removal than the conventional treatment of coagulation-flocculation with FeCl3 and polyelectrolyte. Treated water can be reused in new dyeing processes of cotton fabrics with high quality results.

Photocatalytic Membrane Reactor for the Removal of C.I. Disperse Red 73

After the dyeing process, part of the dyes used to color textile materials are not fixed into the substrate and are discharged into wastewater as residual dyes. In this study, a heterogeneous photocatalytic process combined with microfiltration has been investigated for the removal of C.I. Disperse Red 73 from synthetic textile effluents. The titanium dioxide (TiO2) Aeroxide P25 was selected as photocatalyst. The photocatalytic treatment achieved between 60% and 90% of dye degradation and up to 98% chemical oxygen demand (COD) removal. The influence of different parameters on photocatalytic degradation was studied: pH, initial photocatalyst loading, and dye concentration. The best conditions for dye degradation were pH 4, an initial dye concentration of 50 mg·L−1, and a TiO2 loading of 2 g·L−1. The photocatalytic membrane treatment provided a high quality permeate, which can be reused.

Reuse of Textile Dyeing Effluents Treated with Coupled Nanofiltration and Electrochemical Processes

The reactive dye Cibacron Yellow S-3R was selected to evaluate the feasibility of combining nanofiltration membranes with electrochemical processes to treat textile wastewater. Synthetic dyeing effluents were treated by means of two nanofiltration membranes, Hydracore10 and Hydracore50. Up to 98% of dye removal was achieved. The influence of salt concentration and pH on membrane treatment was studied. The best dye removal yield was achieved at pH 3 in the presence of 60 g/L of NaCl. After the membrane filtration, the concentrate containing high dye concentration was treated by means of an electrochemical process at three different current densities: 33, 83, and 166 mA/cm2. Results showed a lineal relationship between treatment time and applied current density. Both permeates and electrochemically-decoloured effluents were reused in new dyeing processes (100% of permeate and 70% of decoloured concentrates). Dyed fabrics were evaluated with respect to original dyeing. Colour differences were found to be into the acceptance range.

Application of PVDF ultrafiltration membranes to treat and reuse textile wastewater

AbstractIn this work, the feasibility of polyvinylidene difluoride ultrafiltration membranes to treat textile wastewater was studied. The C.I. Disperse Orange 30 and C.I. Disperse Rubine 73 were selected as pollutant for the membrane filtration study. The results showed about 90 and 96% of COD decrease and dye removal, respectively. In addition, very low fouling was observed which demonstrated the feasibility of applying this type of membranes to treat textile wastewater. Finally, after the membrane treatment, 100% of the obtained permeate was reused. Fabrics dyed with the reused water were evaluated with respect to references carried out with softened tap water. No significant colour differences were observed between reference fabrics and the fabrics dyed with the permeate.

Continuous reuse of water and electrolyte from decolorized reactive dyebaths

Abstract In this work, the feasibility of reusing water and salt from reactive dyebaths after electrochemical decolourization was evaluated. Dyeing series of ten reuses with three reactive dyes (Navy Blue Procion H-EXL, Crimson Procion H-EXL and Yellow Procion H-EXL) were carried out (individually and in a trichromie) and color differences and total organic carbon values were measured to study how the successive reuses affect the quality dyeing. The first reuse produced dyeings with low colour differences with respect to a standard dyeing. In the subsequent reuses, colour differences increased until they reached a constant value at the 4th or 5th reuse, following a similar behavior to the organic matter content. At this point, it is determined the percentage of dye increase that allows for continuous dyeing of acceptable quality for the textile industry. To obtain dyeings with acceptable color differences (DE∗ CMC(2:1) ⩽ 1) independent of the number of consecutive reuses, a 30% increase in blue dyestuff a...

Comparison of different wastewater treatments for colour removal of reactive dye baths

AbstractThe generation of high-coloured wastewater is one of the main environmental problems of the textile industry. Reactive dyes are widely used in the dyeing of cellulosic fibres. However, they have low exhaustion degree (70–90%). The degradation of residual dyes by aerobic biological treatment is very poor, being necessary the application of specific treatments. In this work, three different methods for the removal of reactive dyes were compared: electrochemical treatment, coagulation with Moringa oleifera waste and enzymatic treatment with laccase. Two azo bifunctional dyes with different reactive groups were selected: C.I. Reactive Black 5 (vinyl sulphone) and C.I. Reactive Red 231 (chlorotriazine). The influence of pH (5 and 9) and dye hydrolysis on the decolourisation yield was studied. The electrochemical treatment was the most efficient, with 95–100% colour removal yield. The coagulation with M. oleifera waste also achieved high colour removal efficiency (91–94%). Both methods showed an indepen...

Relevance of Toxicity Assessment in Wastewater Treatments: Case Study—Four Fenton Processes Applied to the Mineralization of C.I. Acid Red 14

Fenton and Fenton-like processes, both in homogeneous and heterogeneous phases, have been applied to an aqueous solution containing the dye AR 14 in order to study the mineralization and toxicity of the solutions generated after color elimination. The mineralization of AR 14 occurred slower than the decolorization. The Microtox analysis of the treated solutions showed low toxicity intrinsic to the chemicals used in the process rather than the degradation products obtained after the treatment of the dye solution. The dye degradation for the Fenton oxidation process was initially faster than for the Fenton-like process but after a short time, the four processes showed similar degradation yields. All processes have shown good results being the heterogeneous process the most convenient since the pH adjustment is not necessary, the catalyst is recovered and reused and the generation of contaminated sludge is avoided.

Photoassisted electrochemical treatment of azo and phtalocyanine reactive dyes in the presence of surfactants

An electrochemical treatment (EC) was applied at different intensities to degrade the chromophoric groups of dyes C.I. Reactive Black 5 (RB5) and C.I. Reactive Blue 7 (Rb7) until uncolored species were obtained. Decolorization rate constants of the azo dye RB5 were higher than the phtalocyanine Rb7 ones. In addition, the EC treatment was more efficient at higher intensities, but these conditions significantly increased the generation of undesirable by-products such as chloroform. The combination of EC with UV irradiation (UVEC) drastically minimized the generation of chloroform. The photo-assisted electrochemical treatment was also able to achieve decolorization values of 99%. Finally, mixtures of dyes and surfactants were treated by EC and UVEC. In the presence of surfactants, the decolorization kinetic of dyes was slowed due to the competitive reactions of surfactants degradation. Both methods achieved total decolorization and in both cases, the generation of haloforms was negligible.

Influence of a mixture of metals on PAHs biodegradation processes in soils

In order to assess the effect of mixed pollutants, the influence of different concentration levels of a mixture of metals (Cr, Co, Pb, Mn, Ni, Cu, Zn) on the biodegradation of some PAHs (phenanthrene, fluoranthene, pyrene, benzo[b]fluoranthene and benzo[a]pyrene) in soil samples was evaluated. To do so, groups of microcosms of a natural soil from the region of Sabadell (Barcelona, Spain) were prepared as a reproduction of the native environment at laboratory scale, under controlled conditions. Mixtures of PAHs and metals were carefully selected, according to soil characterization and microbiological growth preliminary assays, and were added to microcosms. These microcosms were analyzed at various times, along two months, to obtain PAHs dissipation time-courses. A first-order kinetic modelling allowed obtaining different rate constants and DT50 values as a function of the metal levels introduced in microcosms. As a general observation, the higher the concentration of metals, the lower the biodegradation of PAHs of 3-4 rings (phenanthrene, fluoranthene and pyrene). On the other hand, no important effect on the biodegradation of higher molecular weight PAHs (benzo[b]fluoranthene and benzo[a]pyrene) was observed at the different concentration levels of metals tested.

Reducing environmental impact of textile waste water by natural coagulants and reuse of effluents

Water scarcity is a global problem, therefore the reuse and recycling of water is promoted in all sectors and it is a real alternative for the conservation of water resources. The industrial sector is a key point in the reuse of water as it is a major consumer of this precious resource. The textile industry consumes more than one hundred liters of water per kilogram of finished fabric during the dyeing and finishing processes. The wastewater generated by this industry is generally coloured and can also contain other recalcitrant compounds. In addition, some textile effluents have high salinity and are highly alkaline. In this work, a new treatment using a natural coagulant, Moringa Oleifera extract, is presented. Coagulant solution was made from moringa seed ground degreased and was tested at variable concentration (1000–5000 mg/l) on different dyeing wastewater samples. Exhausted dyeing liquors and residual washing baths samples were efficiently treated. Up to 90% colour removal was achieved, preserving at the same time the alkaline and saline properties of the water. Consequently, the treated effluents could be reused in new dyeing processes with successful results. It was shown that the implementation of this practice would have considerable environmental and economic benefits.