Biosorption of Direct Fast Scarlet 4BS from aqueous solution using the green-tide-causing marine algae Enteromorpha prolifera

Recent Strategies for the Remediation of Textile Dyes from Wastewater: A Systematic Review

The presence of dye in wastewater causes substantial threats to the environment, and has negative impacts not only on human health but also on the health of other organisms that are part of the ecosystem. Because of the increase in textile manufacturing, the inhabitants of the area, along with other species, are subjected to the potentially hazardous consequences of wastewater discharge from textile and industrial manufacturing. Different types of dyes emanating from textile wastewater have adverse effects on the aquatic environment. Various methods including physical, chemical, and biological strategies are applied in order to reduce the amount of dye pollution in the environment. The development of economical, ecologically acceptable, and efficient strategies for treating dye-containing wastewater is necessary. It has been shown that microbial communities have significant potential for the remediation of hazardous dyes in an environmentally friendly manner. In order to improve the efficacy of dye remediation, numerous cutting-edge strategies, including those based on nanotechnology, microbial biosorbents, bioreactor technology, microbial fuel cells, and genetic engineering, have been utilized. This article addresses the latest developments in physical, chemical, eco-friendly biological and advanced strategies for the efficient mitigation of dye pollution in the environment, along with the related challenges.

Unveiling antibacterial and antioxidant activities of zinc phosphate-based nanosheets synthesized by Aspergillus fumigatus and its application in sustainable decolorization of textile wastewater

BACKGROUND

The development of an environment-friendly nanomaterial with promising antimicrobial and antioxidant properties is highly desirable. The decolorization potentiality of toxic dyes using nanoparticles is a progressively serious worldwide issue.

METHODS

The successful biosynthesis of zinc nanoparticles based on phosphates (ZnP-nps) was performed using the extracellular secretions of Aspergillus fumigatus. The antibacterial activity of the biosynthetic ZnP-nps was investigated against Gram-negative bacteria and Gram-positive bacteria using the agar diffusion assay method. The antioxidant property for the biosynthetic nanomaterial was evaluated by DPPH and H2O2 radical scavenging assay.

RESULTS

Remarkable antibacterial and antiradical scavenging activities of ZnP-nps were observed in a dose-dependent manner. The minimum inhibitory concentration (MIC) for Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli was 25 µg/ml, however, the MIC for Bacillus subtilis was 12.5 µg/ml. The maximum adsorptive performance of nanomaterial was respectively achieved at initial dye concentration of 200 mg/L and 150 mg/L using methylene blue (MB) and methyl orange (MO), where sorbent dosages were 0.5 g for MB and 0.75 g for MB; pH was 8.0 for MB and 4.0 for MO; temperature was 30 °C; contact time was 120 min. The experimental data was better obeyed with Langmuir's isotherm and pseudo-second-order kinetic model (R2 > 0.999). The maximum adsorption capacity (qmax) of MB and MO dyes on nanomaterial were 178.25 mg/g and 50.10 mg/g, respectively. The regenerated nanomaterial, respectively, persist > 90% and 60% for MB and MO after 6 successive cycles. The adsorption capacity of the prepared zinc phosphate nanosheets crystal toward MB and MO, in the present study, was comparable/superior with other previously engineered adsorbents.

CONCLUSIONS

Based on the above results, the biosynthesized ZnP-nanosheets are promising nanomaterial for their application in sustainable dye decolorization processes and they can be employed in controlling different pathogenic bacteria with a potential application as antiradical scavenging agent. Up to our knowledge, this is probably the first study conducted on the green synthesis of ZnP-nanosheets by filamentous fungus and its significant in sustainable dye decolorization.

A review on algae biosorption for the removal of hazardous pollutants from wastewater: Limiting factors, prospects and recommendations

Heavy metals, dyes and pharmaceutical pollutants in water environment are considered as serious threat to the human and animal health globally. Rapid development of industrialization and agricultural activities are the major source for eliminating the toxic pollutants into the aquatic environment. Several conventional treatment methods have been suggested for the removal of emerging contaminants from wastewater. Algal biosorption, among other strategies and techniques, is demonstrating to be a limited technical remedy that is more focused and inherently more efficient and helps remove dangerous contaminants from water sources. The different environmental effects of harmful contaminants, including heavy metals, dyes, and pharmaceutical chemicals, as well as their sources, were briefly compiled in the current review. This paper provides a comprehensive definition of the future possibilities in heavy compound decomposition by using algal technology, from aggregation to numerous biosorption procedures. Functionalized materials produced from algal sources were clearly proposed. This review further highlights the limiting factors of algal biosorption to eliminate the hazardous material. Finally, this study showed how the existence of algae indicates a potential, effective, affordable, and sustainable sorbent biomaterial for minimizing environmental pollution.

Coagulated Mineral Adsorbents for Dye Removal, and Their Process Intensification Using an Agitated Tubular Reactor (ATR)

The aim of this study was to understand the efficacy of widely available minerals as dual-function adsorbers and weighter materials, for the removal of toxic azo-type textile dyes when combined with coprecipitation processes. Specifically, the adsorption of an anionic direct dye was measured on various mineral types with and without the secondary coagulation of iron hydroxide (‘FeOOH’) in both a bench-scale stirred tank, as well as an innovative agitated tubular reactor (ATR). Talc, calcite and modified bentonite were all able to remove 90–95% of the dye at 100 and 200 ppm concentrations, where the kinetics were fitted to a pseudo second-order rate model and adsorption was rapid (<30 min). Physical characterisation of the composite mineral-FeOOH sludges was also completed through particle size and sedimentation measurements, as well as elemental scanning electron microscopy to determine the homogeneity of the minerals in the coagulated structure. Removal of >99% of the dye was achieved for all the coagulated systems, where additionally, they produced significantly enhanced settling rates and bed compression. The greatest settling rate (9 mm min−1) and solids content increase (450% w/w) were observed for the calcium carbonate system, which also displayed the most homogenous distribution. This system was selected for scale-up and benchmarking in the ATR. Dye removal and sediment dispersion in the ATR were enhanced with respect to the bench scale tests, although lower settling rates were observed due to the relatively high shear rate of the agitator. Overall, results highlight the applicability of these cost-effective minerals as both dye adsorbers and sludge separation modifiers to accelerate settling and compression in textile water treatment. Additionally, the work indicates the suitability of the ATR as a flexible, modular alternative to traditional stirred tank reactors.

Adsorption characteristics of methylene blue by a dye-degrading and extracellular polymeric substance -producing strain

Biosorption of dye by microbes and the extracellular polymeric substances (EPS) were of great environmental significance, especially for the dye-degrading and EPS-producing strain. Previous studies were mainly focused on the adsorption capacities and regeneration properties of pure culture, few were on the biosorption of dyes by the dye-degraders and the contributions of EPS on adsorption. In this study, a dye-degrading and EPS-producing strain i.e., Klebsiella oxytoca was used to evaluate its removal capacity to methylene blue. The maximum adsorption capacity (q_e) by the strain was calculated as 145 mg g^-1, which is superior to many reported bio-adsorbents and some synthetic materials. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy results suggested that CO, -NH₂ and P-OH groups were involved in the adsorption. High pressure steam sterilization (HPSS) increased the hydrophilicity of cell wall but did not significantly change the cell structure. Compared with the dead resting cell (DRC), the relative higher q_e obtained by live resting cell (LRC) possibly due to the loss of some cell structure during the HPSS process. Adsorption experiments by EPS-free LRC, confocal laser microscope and three-dimensional excitation-emission matrix fluorescence spectroscopy results confirmed that the EPS played a role in the adsorption of MB dye. The adsorption characteristics of the dye-degrader and the contributions of EPS on adsorption were investigated in detail in this study. The results were benefit for better understanding of the interaction mechanisms between the dye molecules and cells that before the biodegradation process, which were of great significance for the practical usage of residual sludge on removal of dyes.

Phycoremediation of Synthetic Dyes: An Effective and Eco-Friendly Algal Technology for the Dye Abatement

Rapid industrialization leads to serious environmental hazards due to the increase in the release of pollutants into the environment. Industries that use synthetic dyes for different applications are a predominant source for dye contaminants by releasing the dye in wastewater with pretreatment or without treatment directly into the water bodies, making serious water pollution in the environment. Therefore, it is imperative to safeguard the environment from such contaminants and their associated negative impacts. The conventional treatment method that is used to treat dye-contaminated wastewater is generally costly and has a possibility to produce secondary metabolites. Due to the above problems, the biological method is preferable to treat effluent or dye-contaminated wastewater. Phycoremediation is an algae-based eco-friendly dye abatement technique from contaminated environments. This review highlights the phycoremediation of dyes and its underlying mechanisms along with the information on synthetic dyes, classification, hazardous effects, and other major techniques of dye abatement. This review provides a comprehensive insight into several influencing factors such as pH, temperature, contact time, the dose of algae biomass, and agitation speed, as well as functional groups involved in the phycoremediation process.

Biosorption: A Review of the Latest Advances

Biosorption is a variant of sorption techniques in which the sorbent is a material of biological origin. This technique is considered to be low cost and environmentally friendly, and it can be used to remove pollutants from aqueous solutions. The objective of this review is to report on the most significant recent works and most recent advances that have occurred in the last couple of years (2019–2020) in the field of biosorption. Biosorption of metals and organic compounds (dyes, antibiotics and other emerging contaminants) is considered in this review. In addition, the use and possibilities of different forms of biomass (live or dead, modified or immobilized) are also considered.