Biodegradation of Synthetic Effluent Containing CI Direct Red 28 (Congo Red) by Lentinus sp. Laccase Leads to Low Ecotoxicity

Background: Azo dyes are widely used recalcitrant chemicals and may promote environmental hazards. Amongst the known azo dyes is CI Direct Red 28 (C32H22N6Na2O6S2) aka Congo Red (CR), which is a known mutagen and carcinogen. In this regard, this work aimed at the biodegradation of a CR-containing synthetic effluent, and the evaluation of the ecotoxicity of post-treatment residues. Methods: Lentinus sp. Laccase (Lac)-mediated bioremediation of CR was optimized upon added concentrations of sucrose and CuSO4, moreover a standard ecotoxicity assay was performed. Results: Results showed that the addition of 5% sucrose and 2 mM CuSO4 increased CR degradation, with Lac activity at 48 h of 30.2 U mL-1, and at 72 h of 31.9 U mL-1. Moreover, the ecotoxicity assay showcased that CR degradation by Lentinus sp. Lac seemingly generated low ecotoxic byproducts. Conclusion: Given that CR bioremediation byproducts were known to exhibit high toxicity, our results shed light on the use of Lentinus sp. catalytic arsenal to promote proper remediation of azo dyepolluted effluents.

Eco-friendly dyeing of cellulosic fabric using Direct Red 28 and Direct Blue 15 dyes

<p>Sustainability in textiles is now a day’s key demand of consumers and traders, where the process with zero effluent emission or less emission has been considered for aim to utilize the ecofriendly process in direct dyeing of cotton to minimize effluent load. For this purpose, variable amount of Table salt and Glauber salt has been used to achieve maximum exhaustion during direct cotton dyeing. Different dyeing variables have been employed, shade made at the optimum conditions were assessed according to ISO standards. It has been found that 3g/100mL of table salt for Direct dyeing of cotton using 40mL of DR 28 (8pH) at 65oC for 45 min, whereas using 40mL of DB 15 (8pH) for dyeing of cotton at 65 °C for 45min containing 3g/100mL of Glauber slat has given acceptable color characteristics. The reduction in dyeing variable using low salt amount has proved that this method is cost, time and energy efficient process, which can be utilized for dyeing of natural fabrics using various classes of dyes to obtain sustainable textile products.</p>

Microwave Treated Gardenia Jasminoides Leaves for Adsorptive Removal of Direct Red-28 Dye in Environmental Benign Way

In this work, microwave treated Gardenia jasminoides leaves (MTGL) were employed to remove Direct Red-28 (DR) dye from aqueous medium. Most of DR dye contents removed within 30 minutes at pH 2 and 350 ppm dye concentration by 0.02 mg MTGL. Maximum dye adsorbed by MTGL (88.50 mg/g) was approximately triple than non treated simple Gardenia jasminoides leaves (34.13 mg/g). Adsorption modelling of equilibrium data indicated that removal of DR dye by MTGL followed Langmuir, Freundlich and pseudo-second order kinetic models, having exothermic nature. Desorption studies indicated the reusability of MTGL on larger scale. So it is clear that Gardenia jasminoide leaves can be used on larger scale for anionic dye removal after treatment with formalin in efficient manner.

Toxicity and removal of Direct Red 28 diazo dye in living polymeric systems

Aquatic environments are often contaminated with various compounds, with potential toxicity towards aquatic organisms, which may enter the food chain. Azo dyes are used in various industries and contamination of waters has been reported. The present paper assesses the toxicity of the synthetic, water soluble Congo Red dye towards Lemna minor from a physiological and cytogenetical point of view. The dye was tested in 5-5000 ppm concentrations. Total frond surface, root growth and fresh mass reductions were registered from 5 ppm dye concentration, with a concentration-dependent response and calculated EC50 of 1530 ppm. Plant growth was completely inhibited above 2500 ppm. Dye accumulation was observed in tissues, along with necrosis formation. Chlorophyll a contents decreased, while carotenoid contents increased above 2500 ppm. Significant inhibition of PSII efficiency was recorded above 1000 ppm. Mitotic indices were decreased at 5 and 1000 ppm dye and were 0 at 5000 ppm. The number of chromosomal aberrations significantly increased at 5 and 1000 ppm dye. The growth medium was decontaminated up to 56% at 250 ppm dye concentration by Lemna plants. Congo Red azo dye presented toxicity towards Lemna minor, from a physiological and cyotgenetical point of view, especially at higher concentrations. In the same time, a phytoremediation potential of duckweed with respect to the tested dye was demonstrated.

Synthesis of Ag–SiO2–APTES Nanocomposites by Blending Poly(Vinylidene Fluoride) Membrane with Potential Applications on Dye Wastewater Treatment

In the study, the Ag–SiO2–APTES nanocomposite was synthesized via the self-assembly method to prepare Ag–SiO2 and subsequently used 3-aminopropyltriethoxysilane (APTES) to functionalize its surface. The as-prepared Ag–SiO2–APTES nanocomposite was embedded into poly(vinylidene fluoride) (PVDF) membrane by the co-blending way to fabricate the Ag–SiO2–APTES membrane. The Ag–SiO2–APTES nanocomposites were characterized by X-ray diffraction (XRD). These membrane materials were characterized by field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM) and FT-IR spectra. The performance of membrane was investigated simultaneously for removing the organic dye methylene blue (MB), Rhodamine B, Direct Red 28 and anti-microbial ability. The experimental results demonstrated that the Ag–SiO2–APTES modified membrane were presented to be more hydrophilic with a contact angle 55.6[Formula: see text], whereas the pristine PVDF membrane was 81.8[Formula: see text]. The dye rejection ratios were also improved after adding Ag–SiO2–APTES, which reached 86.8% for MB, 87% Rhodamine B, 88% for Direct Red 28, besides, the removal rate of MB was about 98.7% at pH [Formula: see text] 11. More importantly, the Ag–SiO2–APTES membranes exhibited excellent antifouling properties for treating MB solution and could reach 85% of flux recovery ratio after four cyclic experiment. Finally, via inhibition zone method of antimicrobial test Ag–SiO2–APTES membrane exhibited the antimicrobial activity against Escherichia coli (E. coli) excellently. The novel antifouling and antibacterial Ag–SiO2–APTES membrane has a potential for dye wastewater treatment and water purity.