Construction of integrated system for the treatment of Acid orange 7 dye from wastewater: Optimization and growth kinetic study

Biodegradation of Congo Red Dye Using Lysinibacillus Species in a Moving Bed Biofilm Reactor: Continuous Study and Kinetic Evaluation

The objective of this work was to develop a low-cost and efficient biocarrier for biodegradation of azo dye (i.e., Congo red (CR) dye). The potential bacterial species, i.e., Lysinibacillus fusiformis KLM1 and Lysinibacillus macrolides KLM2, were isolated from the dye-contaminated site. These bacterial species were immobilized onto the polypropylene-polyurethane foam (PP-PUF) and employed in a moving bed biofilm reactor (MBBR) for the treatment of CR dye. The effectiveness of the MBBR was investigated by operating the bioreactor in a continuous mode at various initial CR dye concentrations (50-250 mg/L) for 113 days. The removal efficiency was found in the range of 88.4-64.6% when the initial dye concentration was varied from 50 to 250 mg/L. The maximum elimination capacity (EC) of 213.18 mg/L.d was found at 250 mg/L of CR dye concentration. In addition, the CR dye utilization rate in the MBBR was studied by using two kinetics, namely, first-order and second-order (Grau) models. The high regression coefficients (R2 > 0.97) and the satisfactory root mean square (RMSE) values (0.00096-0.02610) indicated the reasonable prediction of CR dye degradation rate by the Grau model.

Understanding the biodegradation pathways of azo dyes by immobilized white-rot fungus, Trametes hirsuta D7, using UPLC-PDA-FTICR MS supported by in silico simulations and toxicity assessment

No biodegradation methods are absolute in the treatment of all textile dyes, which leads to structure-dependent degradation. In this study, biodegradation of three azo dyes, reactive black 5 (RB5), acid blue 113 (AB113), and acid orange 7 (AO7), was investigated using an immobilized fungus, Trametes hirsuta D7. The degraded metabolites were identified using UPLC-PDA-FTICR MS and the biodegradation pathway followed was proposed. RB5 (92%) and AB113 (97%) were effectively degraded, whereas only 30% of AO7 was degraded. Molecular docking simulations were performed to determine the reason behind the poor degradation of AO7. Weak binding affinity, deficiency in H-bonding interactions, and the absence of interactions between the azo (-NN-) group and active residues of the model laccase enzyme were responsible for the low degradation efficiency of AO7. Furthermore, cytotoxicity and genotoxicity assays confirmed that the fungus-treated dye produced non-toxic metabolites. The observations of this study will be useful for understanding and further improving enzymatic dye biodegradation.

Preparation and Superstrong Adsorption of a Novel La(Ⅲ)-Crosslinked Alginate/Modified Diatomite Macroparticle Composite for Anionic Dyes Removal from Aqueous Solutions

In order to solve the problem of dye pollution of the water environment, a green macroparticle composite (CPAM-Dia/SA-La) as a bioadsorbent was prepared through a sodium alginate (SA) reaction with a polyacrylamide (CPAM)-modified diatomite (Dia) and further La(III) ion crosslinking polymerization, and characterized by various analytical methods. The important preparation and adsorption conditions of the composite were explored by the adsorption of Acid blue 113 (AB 113) and Congo red (CR) dyes. The dye adsorption efficiency was evaluated. The results show that CPAM-Dia/SA-La composite prepared under the optimized conditions displays superstrong adsorption capacities of 2907 and 1578 mg/g for AB 113 and CR and almost 100% removal efficiency within 60 min adsorption time at pH 2.0 and 298 K, and they decrease slightly with the pH increase to 10. The fitting of equilibrium data to the Langmuir model is the best and the adsorption kinetic processes can be expressed by the Pseudo-second-order kinetic model. The adsorption processes are both spontaneous and exothermic. The analysis results of FT-IR and XPS revealed that the superstrong adsorption of CPAM-Dia/SA-La for dyes. The composite adsorbed by the dye can be recycled. CPAM-Dia/SA-La is a promising biosorbent for dye wastewater treatment.

Biodegradation of Congo red dye using polyurethane foam-based biocarrier combined with activated carbon and sodium alginate: Batch and continuous study

Dyes are an important class of organic pollutants and are well known for their adverse effects on aquatic life and human beings. In this work, an effort has been made to treat the dye-containing wastewater using modified biocarriers in packed bed bioreactors (PBBRs). Lysinibacillus sp. immobilized polyurethane foam combined with activated carbon and sodium alginate was used for the biodegradation of Congo red dye. The optimum values of process time, glucose concentration, and dye concentration were obtained to be 4.0 days, 2.0 g/L, and 50 mg/L, respectively. The maximum dye removal efficiency (RE) of 92.63 % was obtained at the optimized conditions. The continuous PBBR offered a maximum RE and elimination capacity of 90.73% and 10.89 mg/L. d, respectively, at an inlet loading rate of 12 mg/L. d. Moreover, the growth kinetic of Lysinibacillus sp. was well predicted by the Andrew-Haldane model with a regression coefficient of 0.98.

Highly efficient bio-adsorption of Malachite green using Chinese Fan-Palm Biochar (Livistona chinensis)

The discharge of effluents from the textile industry is a multidimensional problem that affects the ecosystem in many ways. Though many new technologies are being developed, it remains to be seen which of those can be practiced in a real scenario. The current investigation attempts to absorb the Malachite Green, an effluent from textile dye using Chinese Fan Palm Seed Biochar. Accordingly, biochar was prepared using fruits of Chinese Fan Palm (Livistona chinensis) tree. The fruit also yielded a significant amount of biochar and bio-oil. 1.346 kg of fresh and cleaned fruit was fast pyrolyzed at 500 °C in a laboratory-scale Pyrolyzer resulting in 0.487 kg of biochar and 0.803 L of bio-oil. The remaining fruit matter was converted to gaseous products. The kinetics of dye removal were studied and the parameters were determined. The study advocates that the Langmuir isotherm model simulates the adsorption experiment, to a good extent. From the plot, the maximum (monolayer) adsorption capacity, Q_m was determined to be 21.4 mg/g. The suitability of the Langmuir isotherm model onto biochar was established by the high correlation coefficient, R² that was higher than 0.97.

Constructing Er-Doped ZnO/CuS/Au Core-Shell Nanowires with Enhanced Photocatalytic and SERS Properties

In this study, we fabricated Er-doped ZnO/CuS/Au core-shell nanowires using two-step wet chemical methods and an ion-sputtering method on a glass substrate as a bifunctional photocatalytic and surface-enhanced Raman scattering (SERS) substrate. The characteristic properties of as-prepared photocatalysts were confirmed by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy, DR/UV-Vis spectroscopy, and photoluminescence spectroscopy. Compared with Er-doped ZnO nanowires and Er-doped ZnO/CuS core-shell nanowires, Er-doped ZnO/CuS/Au core-shell nanowires exhibited remarkably photocatalytic activity to degrade acid orange 7 solutions under blue LED light. These results ascribed to the Er-doped ZnO/CuS/Au core-shell nanowires can enhance the visible-light absorbance and the separation efficiency of photogenerated electron-hole pairs, inducing their higher photocatalytic activity under blue LED light. In addition, Er-doped ZnO/CuS/Au core-shell nanowires exhibit high sensitivity, a low detection limit (10−6 M), uniformity, recyclability, and stability of SERS performance for detected acid orange 7.