RESUMEN

In the study, sol-gel based TiO2 nanoparticles (NPs) were doped by Cu(II), and the surface of cotton fabric was coated with Cu-doped TiO2 NPs to develop self-cleaning and antibacterial properties. Coffee stains were introduced on the modified cotton fabric and under suntest illumination; a decrease in the color of coffee stain was followed over time via K/S value to determine self-cleaning performance. The photocurrent in a photoelectrocatalytic reactor was measured to evaluate the photocatalytic effect of Cu(II) doping. TiO2 NPs showed self-cleaning and antibacterial effects under UV-illuminated conditions. However, no effects were observed under dark (non-illuminated) conditions. The modified textiles with Cu(II) doped TiO2 NPs showed antibacterial activity against E. coli under light and dark conditions. Under the 2 h illumination period, fluctuating color changes were observed on the raw cotton fabric, and stains remained on the fabric while 78% and 100% color removals were achieved in the cotton fabrics coated by Cu doped TiO2 NPs in 1 h and 2 h, respectively.

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RESUMEN

The Bipolar Membrane Electrodialysis process (BPMED) can produce valuable chemicals such as acid (HCl, H2SO4, etc.) and base (NaOH) from saline and brackish waters under the influence of an electrical field. In this study, BPMED was used to recover wastewater and salt in biologically treated textile wastewater (BTTWW). BPMED process, with and without pre-treatment (softening and ozonation), was evaluated under different operational conditions. Water quality parameters (color, remaining total organic carbon, hardness, etc.) in the acid, base and filtrated effluents of the BPMED process were evaluated for acid, base, and wastewater reuse purposes. Ozone oxidation decreased 90% of color and 37% of chemical oxygen demand (COD) in BTTWW. As a result, dye fouling on the anion exchange membrane of the BPMED process was reduced. Subsequently, over 90% desalination efficiency was achieved in a shorter period. Generated acid, base, and effluent wastewater of the BPMED process were found to be reusable in wet textile processes. Results indicated that pre-ozonation and subsequent BPMED membrane systems might be a promising solution in converging to a zero discharge approach in the textile industry.

RESUMEN

In this study, a novel photoelectrocatalytic membrane (PECM) reactor was tested as an option for the desalination, disinfection, and detoxification of biologically treated textile wastewater (BTTWW), with the aim to reuse it in hydroponic farming. The anionic ion exchange (IEX) process was used before PECM treatment to remove toxic residual dyes. The toxicity evaluation for every effluent was carried out using the Vibrio fischeri, Microtox® test protocol. The disinfection effect of the PECM reactor was studied against E. coli. After PECM treatment, the 78.7% toxicity level of the BTTWW was reduced to 14.6%. However, photocatalytic desalination during treatment was found to be slow (2.5 mg L-1 min-1 at 1 V potential). The reactor demonstrated approximately 52% COD and 63% TOC removal efficiency. The effects of wastewater reuse on hydroponic production were comparatively investigated by following the growth of the lettuce plant. A detrimental effect was observed on the lettuce plant by the reuse of BTTWW, while no negative impact was reported using the PECM treated textile wastewater. In addition, all macro/micronutrient elements in the PECM treated textile wastewater were recovered by hydroponic farming, and the PECM treatment may be an eco-safe wastewater reuse method for crop irrigation.

RESUMEN

The galvanizing industry uses the concentrated hydrochloric acid in its metal surface treatment processes known as pickling. Every year tons of waste acid solutions polluted with metals ions are discharged to the environment after neutralization process. In this study, a novel photoelectrochemical reactor is designed and developed for the production of hydrogen and chlorine gas from spent hydrochloric acid generated in the galvanizing industry. The novel reactor design allows all the hydrogen gas to flow from the reactor without any dead zone in the cathode compartment, while chlorine gas is carried out with aqueous 5 M HCl at the surface of the illuminated photoanode without any dissolution. Further, the unique design of the cathode corrosion-resistant high surface area (3 × the anode) results in good proton and H+ transfer rate while the TiO2 coated photoanode further enhances the charge transfer process and chlorine gas production. The characterization of the coated stainless steel is tested by the energy-dispersive X-ray (EDX) analysis and scanning electron microscope (SEM) images. The photoelectrochemical potentiostatic experiments with and without sunlight are performed on the reactor. The hydrogen and chlorine gas production rates are observed as 3 mL/min and 0.5 mL/min, respectively. Also, a comprehensive thermodynamic analysis of the photoelectrochemical reactor is conducted, and energy, exergy, and quantum efficiencies are found as 45.55%, 73.75%, and 6%, respectively. The exergoeconomic assessment study shows that the lowest exergy cost rate is achieved with sunlight illumination for a hydrogen exergy cost of 1.7 $/kg and chlorine exergy cost rate of 0.3 $/kg at an applied potential of 2 V.

RESUMEN

Ozonation of chloride-rich textile wastewater is a common pretreatment practice in order to increase biodegradability and therefore meet the discharge limits. This study is the first to investigate ozone-chloride/bromide interactions and formation of hazardous adsorbable organic halogens (AOX) in real textile wastewater. Initially effect of ozonation on chloride-rich real textile wastewater samples were investigated for adsorbable organic halogens (AOX) formation, biodegradability and toxicity. After 15 min of ozonation, maximum levels of chlorine/bromine generation (0.3 mg/l) and AOX formation (399 mg/l) were reached. OUR and SOUR levels both increased by approximately 58%. Daphnia magna toxicity peaked at 100% for 10 min ozonated sample. Considering adverse effects of ozonation on chloride-rich textile industry effluents, we proposed replacement of NaCl with Na2SO4. Comparative ozonation experiments were carried out for both chloride and sulfate containing synthetic dyeing wastewater samples. Results showed that use of sulfate in reactive dyeing increased biodegradability and decreased acute toxicity. Although sulfate is preferred over chloride for more effective dyeing performance, the switch has been hampered due to sodium sulfate's higher unit cost. However, consideration of indirect costs such as contributions to biodegradability, toxicity, water and salt recovery shall facilitate textile industry's switch from chloride to sulfate.

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