Integrating bioremediation of textile wastewater with biodiesel production using microalgae (Chlorella vulgaris).

Microalgae-led wastewater treatment is a promising biorefinery approach to promote environmental and economical sustainability. In this study, Chlorella vulgaris (C. vulgaris) was employed for the bioremediation of textile wastewater (TWW) and biodiesel production. C. vulgaris is cultivated in undiluted and diluted TWW (50%). Cultivation in freshwater containing BG11 medium was set as a control. Results show the highest growth (1.62 ± 0.12 OD680) in diluted TWW followed by BG11 medium (1.56 ± 0.15 OD680) and undiluted TWW (0.89 ± 0.11 OD680). The highest methylene blue decolorization of 99.7% was observed in diluted TWW as compared to 98.5% in undiluted TWW. Morever, COD removal efficiency was also higher (99.7 ± 4.2%) in diluted TWW than BG11 medium (94.4 ± 3.5%) and undiluted TWW (76.3 ± 2.8%). For all treatment, more than 80% nitrogen and phosphorous removal were achieved. Otther than this, fatty acids methyl ester (FAME) yield in diluted TWW was higher (11.07 mg g-1) than the undiluted TWW (9.12 mg L-1). Major FAME were palmitic acid (C16:0) and linolenoic acid (C18:3) which are suitable for biodiesel production. All these results suggest that C. vulgaris can be cultivated in both diluted and undiluted TWW for biodiesel production. However, cultivation in undiluted TWW is more favorable as it displaces the need for freshwater addition in the growth medium.

Integrating adsorption and photocatalysis: A cost effective strategy for textile wastewater treatment using hybrid biochar-TiO2 composite.

TiO2 based photocatalysts are extensively used for textile wastewater treatment as they are ecofriendly, inexpensive, easily available, nontoxic and have higher photostabililty. However, their wider band gap, charge carrier's recombination, and utilization of light absorbance limits their performance. In the present work, a hybrid biochar-TiO2 composite (BCT) has been synthesized by a facile synthesis strategy to overcome these problems. These photocatalysts are characterized using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), UV-vis diffuse reflectance spectra (DRS), and photoluminescence (PL) to evaluate their crystallinity, morphology, functional groups, bandgap energy and charge separation properties, respectively. The photodegradation of simulated textile wastewater is analyzed using hybrid composites. The hybrid biochar-TiO2 composite showed higher charge separation, slow recombination of electron-hole pairs, and enhanced light absorption as compared to control (pure TiO2 and BC alone). 99.20 % photodegradation efficiency of dye-simulated wastewater is achieved employing optimum hybrid composite, while the pure biochar and TiO2 samples exhibits 85.20 % and 42.60 % efficiencies, respectively. The maximum adsorption capacity is obtained for hybrid biochar-TiO2 sample, 74.30 mgg-1 in comparison to biochar (30.40 mgg-1) and pure TiO2 (1.50 mgg-1). The results show that hybrid biochar-TiO2 composites can perform in the target application of organic industrial pollutant removal.

Carbon Nanotubes Incorporated Z-Scheme Assembly of AgBr/TiO2 for Photocatalytic Hydrogen Production under Visible Light Irradiations.

Photocatalytic H2 production is a promising strategy toward green energy and alternative to carbon-based fuels which are the root cause of global warming and pollution. In this study, carbon nanotubes (CNTs) incorporated Z-scheme assembly of AgBr/TiO2 was developed for photocatalytic H2 production under visible light irradiations. Synthesized photocatalysts were characterized through transmission electron microscope (TEM), X-ray photoelectron spectra (XPS), X-ray diffractometer (XRD), Fourier transform infrared (FTIR), photoluminescence spectra (PL), Brunauer Emmet-Teller(BET), and UV-vis spectroscopy analysis techniques. The composite photocatalysts exhibited a H2 production of 477 ppm which was three-folds higher than that produced by TiO2. The good performance was attributed to the strong interaction of three components and the reduced charge recombination, which was 89 and 56.3 times lower than the TiO2 and AgBr/TiO2. Furthermore, the role of surface acidic and basic groups was assessed and the photocatalytic results demonstrated the importance of surface functional groups. In addition, the composites exhibited stability and reusability for five consecutive cycles of reaction. Thus, improved performance of the photocatalyst was credited to the CNTs as an electron mediator, surface functional groups, higher surface area, enhanced charge separation and extended visible light absorption edge. This work provides new development of Z-scheme photocatalysts for sustainable H2 production.