Biosorption of synthetic dyes (Direct Red 89 and Reactive Green 12) as an ecological refining step in textile effluent treatment

Biodecolorization and biodegradation of Reactive Green 12 textile industry dye and their post-degradation phytotoxicity-genotoxicity assessments

The employment of versatile bacterial strains for the efficient degradation of carcinogenic textile dyes is a sustainable technology of bioremediation for a neat, clean, and evergreen globe. The present study has explored the eco-friendly degradation of complex Reactive Green 12 azo dye to its non-toxic metabolites for safe disposal in an open environment. The bacterial degradation was performed with the variable concentrations (50, 100, 200, 400, and 500 mg/L) of Reactive Green 12 dye. The degradation and toxicity of the dye were validated by high-performance liquid chromatography, Fourier infrared spectroscopy analysis, and phytotoxicity and genotoxicity assay, respectively. The highest 97.8% decolorization was achieved within 12 h. Alternations in the peaks and retentions, thus, along with modifications in the functional groups and chemical bonds, confirmed the degradation of Reactive Green 12. The disappearance of a major peak at 1450 cm-1 corresponding to the -N=N- azo link validated the breaking of azo bonds and degradation of the parent dye. The 100% germination of Triticum aestivum seed and healthy growth of plants verified the lost toxicity of degraded dye. Moreover, the chromosomal aberration of Allium cepa root cell treatment also validated the removal of toxicity through bacterial degradation. Thereafter, for efficient degradation of textile dye, the bacterium is recommended for adaptation to the sustainable degradation of dye and wastewater for further application of degraded metabolites in crop irrigation for sustainable agriculture.

Direct red 89 dye degradation by advanced oxidation process using sulfite and zero valent under ultraviolet irradiation: Toxicity assessment and adaptive neuro-fuzzy inference systems modeling

Sulfate-based advanced oxidation process mediated by zero-valent iron (ZVI) and ultraviolet radiation for the decomposition of sulfite salts resulted in the formation of strong oxidizing species (sulfate and hydroxide radicals) in aqueous solution is reported. Degradation of direct red 89 (DR89) dye via UV/ZVI/sulfite process was systematically investigated to evaluate the effect of pH, ZVI dose, sulfite, initial DR89 concentration, and reaction time on DR89 degradation. The synergy factor of UV/ZVI/sulfite process was found to be 2.23-times higher than the individual processes including ZVI, sulfite and UV. By increasing the ZVI dose from 100 mg/L to 300 mg/L, dye degradation was linearly enhanced from 67.12 ± 3.36% to 82.40 ± 4.12% by the UV/ZVI/sulfite process due to enhanced ZVI corrosion and sulfite activation. The highest degradation efficiency of 99.61 ± 0.02% was observed at pH of 5.0, [ZVI]₀ = 300 mg/L, and [sulfite]₀ = 400 mg/L. Toxicity assessment by Lepidium sativum demonstrated that treated dye solution by UV/ZVI/sulfite was within the non-toxic range. The application of optimal adaptive neuro-fuzzy inference system (ANFIS) to predict DR89 degradation indicated high accuracy of ANFIS model (R² = 0.97 and RMSE = 0.051) via the UV/ZVI/sulfite process. It is suggested that UV/ZVI/sulfite process is suitable for industrial wastewater treatment.

Hybrid magnetic core-shell TiO2@CoFe3O4 composite towards visible light-driven photodegradation of Methylene blue dye and the heavy metal adsorption: isotherm and kinetic study

Magnetic core-shell TiO₂@CoFe₃O₄ (TCM) composite photocatalytic particles with a core-shell structure were synthesized by the co-precipitation method as a novel catalyst for methylene blue (MB) dye degradation and adsorption efficiency of heavy-metal ion Pb(II) from aqueous solution. Various analytical techniques have verified the formation of the TCM core-shell through TEM, XRD, FT-IR, Raman, PL, and UV analysis. The presence of TiO₂ and cobalt magnetite in the TCM core shell is confirmed by XRD analysis. The formation of a homogenous CoFe₃O₄shell on TiO₂ spheres is confirmed by HR-TEM investigation. TiO₂ nanoparticle has a rutile structure with an average crystallite size of about 57.44 and a TCM core-shell of about 64.62 nm. From UV and PL studies, it was found that the core shell absorbs the visible range of the electromagnetic spectrum, which improves the effective separation between photo carriers. This study focused on several factors that influence metal ion adsorption, including initial concentrations, adsorbent dose, pH, and contact time. The TCM nanocomposite successfully separated the heavy metal ion Pb(II) from aqueous solutions, and the model predictions exactly matched the experimental results. For TCM material, the maximum adsorption efficiency for Pb(II) was 33.09 mg/g. The photocatalytic performance of TiO₂ and TCM is about 12% and 91% after 60 min for MB dye degradation. It was found that TiO₂@CoFe₃O₄ core-shell nanoparticles perform better as photo catalysts than pure TiO₂ and CoFe₃O₄due to their high efficiency and reusability. Furthermore, the analysis revealed that heavy metal adsorption from aqueous solutions could be reused over seven cycles with no adsorption capacity modification.

Optimization of the decolorization conditions of Rose Bengal by using Aspergillus niger TF05 and a decolorization mechanism

Aspergillus niger TF05 was applied to decolorize Rose Bengal dye. The effects of carbon source, nitrogen source, metal ion and spore concentration on Rose Bengal treatment with A. niger TF05 were studied. A Plackett–Burman design (PBD) and a uniform design (UD) were used to optimize the decolorization conditions of A. niger TF05 and enhance its decolorization effect. The mechanism of Rose Bengal decolorization by A. niger TF05 was examined by analysing degradation products via UV–visible light spectroscopy, IR spectroscopy and GC-MS. The best decolorization effect was achieved in the single factor test with glucose and ammonium chloride as carbon and nitrogen sources, respectively. Mg²⁺ was an essential ion that could improve the mould ball state and adsorption efficiency if the spore concentration was maintained at 10⁶ spores ml^–1. The optimal decolorization conditions obtained using the PBD and UD methods were 11.5 g l⁻¹ glucose, 6.5 g l⁻¹ ammonium chloride, 0.4 g l⁻¹ magnesium sulphate, pH 5.8, 28 °C, 140 r.p.m. rotational speed, 0.18 g l⁻¹ dye concentration, 0.5 ml of inocula and 120 h decolorization time. Under these conditions, the maximum decolorization rate was 106%. Spectral analysis suggested that the absorption peak of the product changed clearly after decolorization; GC-MS analysis revealed that the intermediate product tetrachlorophthalic anhydride formed after decolorization. The combined use of the PBD and UD methods can optimize multi-factor experiments. A. niger TF05 decolorized Rose Bengal during intracellular enzymatic degradation after adsorption.

Magnetically recyclable copper doped core-shell Fe3O4@TiO2@Cu nanocomposites for wastewater remediation

The smart magnetic nanocomposites have been doped to diminish the energy bandgap of the photocatalyst and to permit recovering of the photocatalyst after the wastewater treatment. The core-shell Fe3O4@TiO2 nanocomposite was synthesised by the hydrothermal method using titanium butoxide as a precursor. The nanocomposites were examined by XRD, VSM, UV-Vis, and TEM techniques. The energy band gap of core-shell Fe3O4@TiO2 nanocomposite is 3.5 eV. Doping of copper with a concentration of 1, 2, and 3 wt% into TiO2 shell was done to increase the performance of photocatalyst. The Fe3O4/PVP@TiO2@Cu photocatalyst was used for dye wastewater treatment. The energy bandgap decreased to 2.2 eV after copper doping into the TiO2 shell specified that copper-doped nanocomposite could be an outstanding photocatalyst. The photocatalytic activity was carried out using methylene blue(MB) and methyl orange (MO) under sunlight. About 65% of methylene blue and 85% of methyl orange degradation was done using Cu (3wt %) doped Fe3O4@TiO2 nanocomposite. These photocatalysts can be easily withdrawn with a magnetic field. The Fe3O4/PVP@TiO2@Cu photocatalyst has been demonstrated to be very functional or effective for the degradation of MB and MO dyes using solar illumination.

Diversity of Synthetic Dyes from Textile Industries, Discharge Impacts and Treatment Methods

Natural dyes have been used from ancient times for multiple purposes, most importantly in the field of textile dying. The increasing demand and excessive costs of natural dye extraction engendered the discovery of synthetic dyes from petrochemical compounds. Nowadays, they are dominating the textile market, with nearly 8 × 105 tons produced per year due to their wide range of color pigments and consistent coloration. Textile industries consume huge amounts of water in the dyeing processes, making it hard to treat the enormous quantities of this hazardous wastewater. Thus, they have harmful impacts when discharged in non-treated or partially treated forms in the environment (air, soil, plants and water), causing several human diseases. In the present work we focused on synthetic dyes. We started by studying their classification which depended on the nature of the manufactured fiber (cellulose, protein and synthetic fiber dyes). Then, we mentioned the characteristics of synthetic dyes, however, we focused more on their negative impacts on the ecosystem (soil, plants, water and air) and on humans. Lastly, we discussed the applied physical, chemical and biological strategies solely or in combination for textile dye wastewater treatments. Additionally, we described the newly established nanotechnology which achieves complete discharge decontamination.

Influence of co-existing cations and anions on removal of direct red 89 dye from synthetic wastewater by hydrodynamic cavitation process: An empirical modeling

In the present study the evaluation of Direct Red 89 (DR89) dye removal from synthetic wastewater by a lab-scale hydrodynamic cavitation (HC) process has been investigated under different operational conditions; the influence of co-existing cations and anions was applied using synthetic wastewater to assess whether the DR89 removal was enhanced. To study the effect of operational parameters, an empirical approach was adopted for the modeling of the HC process. The results showed that the DR89 degradation rate was strongly influenced by solution pH, reaction time and initial DR89 concentration. The removal efficiencies of DR89 were enhanced remarkably with the reaction time increment. When the initial concentration of DR89 increased from 30 to 90 mg/L, the DR89 removal efficiency decreased from 36.3 ± 3.8% to 17.5 ± 2.5%. In addition, the highest DR89 removal efficiency (75.4 ± 3.4%) was observed at a solution pH of 3. At a solution pH of 8, the DR89 removal efficiency was 18.4 ± 1.1%. An initial DR89 concentration of 80 mg/L was 75.4 ± 5.1% degraded after 130 min at a solution pH of 3. The results indicated that a synergistic effect occurred due to the added ions except for HCO₃^-. The removal of DR89 by the HC process was extremely enhanced with NO₃‾ ions with synergetic index higher than 2.5. Kinetic studies revealed that the decolorization of DR89 by HC followed a first order kinetic mechanism. The comparison between the predicted results of the empirical model and experimental data was also conducted. The empirical model described the DR89 removal efficiency under different conditions (R²: 0.93) and the results showed the HC reaction to be a useful technology for the treatment of dye in the textile wastewater.

Two-Sided Surface Oxidized Cellulose Membranes Modified with PEI: Preparation, Characterization and Application for Dyes Removal

Porous regenerated cellulose (RC) membranes were prepared with cotton linter pulp as a raw material. These membranes were first oxidized on both sides by a modified (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) oxidation system using a controlled oxidation reaction technique. Then, the oxidized RC membranes were functionalized with polyethylenimine (PEI) via the glutaraldehyde crosslinking method to obtain bifunctional (carboxyl and amino) porous RC membranes, as revealed by Fourier transform infrared spectroscopy (FT-IR), elemental analysis and zeta potential measurement. The scanning electron microscopy (SEM) and the tests of the mechanical properties and permeability characteristics of modified RC membranes demonstrated that the porous structure and certain mechanical properties could be retained. The adsorption performance of the modified membranes towards dyes was subsequently investigated. The modified membranes displayed good adsorption capacities, rapid adsorption equilibrium and removal efficiencies towards both anionic (xylenol orange (XO)) and cationic (methylene blue (MB)) dyes, making them suitable bioadsorbents for wastewater treatment.

Bioaccumulation and toxicity assessment of irrigation water contaminated with boron (B) using duckweed (Lemna gibba L.) in a batch reactor system

The present study assesses ability of Lemna gibba L. using a batch reactor approach to bioaccumulation boron (B) from irrigation waters which were collected from a stream in largest borax reserve all over the world. The important note that bioaccumulation of B from irrigation water was first analyzed for first time in a risk assessment study using a Lemna species exposed to various B concentrations. Boron toxicity was evaluated through plant growth and biomass production during phytoremediation process. The result from the present experiment indicated that L. gibba was capable of removing 19-63% B from irrigation water depending upon contaminated level or initial concentration. We also found that B was removed from aqueous solution following pseudo second order kinetic model and Langmuir isotherm model better fitted equilibrium obtained for B phytoremediation. Maximum B accumulation in L. gibba was determined as 2088mgkg^-1 at average inflow B concentration 17.39mgL^-1 at the end of the experiment. Conversely, maximum bioconcentration factor obtained at lowest inflow B concentrations were 232 for L. gibba. The present study suggested that L. gibba was very useful B accumulator, and thus L. gibba-based techniques could be a reasonable phytoremediation option to remove B directly from water sources contaminated with B.

Bioremoval of the azo dye Congo Red by the microalga Chlorella vulgaris

Discharge of dye-containing wastewater by the textile industry can adversely affect aquatic ecosystems and human health. Bioremoval is an alternative to industrial processes for detoxifying water contaminated with dyes. In this work, active and inactive biomass of the microalga Chlorella vulgaris was assayed for the ability to remove Congo Red (CR) dye from aqueous solutions. Through biosorption and biodegradation processes, Chlorella vulgaris was able to remove 83 and 58 % of dye at concentrations of 5 and 25 mg L(-1), respectively. The maximum adsorption capacity at equilibrium was 200 mg g(-1). The Langmuir model best described the experimental equilibrium data. The acute toxicity test (48 h) with two species of cladocerans indicated that the toxicity of the dye in the effluent was significantly decreased compared to the initial concentrations in the influent. Daphnia magna was the species less sensitive to dye (EC50 = 17.0 mg L(-1)), followed by Ceriodaphnia dubia (EC50 = 3.32 mg L(-1)). These results show that Chlorella vulgaris significantly reduced the dye concentration and toxicity. Therefore, this method may be a viable option for the treatment of this type of effluent.

Comparison of biosorption and phytoremediation of cadmium and methyl parathion, a case-study with live Lemna gibba and Lemna gibba powder

Heavy metals and pesticides can be adsorbed by several biomasses such as living or non-living aquatic plants. In this study adsorption properties of live Lemna gibba and Lemna gibba powder were investigated with regard to cadmium and methyl parathion (MP). Toxicity data (IC50) on live L. gibba indicated that the period of four days was adequate for phytoremediation. Initial adsorption studies showed that both adsorbents were capable of removing cadmium and methyl parathion. Cadmium and methyl parathion adsorption onto L. gibba powder was fast and equilibrium was attained within 120min. The adsorption data could be well interpreted by the Freundlich model. The KF were: 7.8963 (Cd(2+)/ live Lemna); 0.7300 (MP/live Lemna); 11.5813 (Cd(2+)/Lemna powder); 1.1852 (MP/Lemna powder) indicating that Cd(2+) was more efficiently removed by both biosorbents than MP. Adsorption kinetics for cadmium and methyl parathion in both systems and rate constants were determined for each contaminant. It was found that the overall adsorption process was best described by pseudo-second-order kinetics. Boyd model and external mass-transfer expression were tested. It was concluded that cadmium and methyl parathion sorption onto Lemna powder is governed by film diffusion.