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Cationic and anionic dye adsorption by agricultural solid wastes: A comprehensive review

Disposal of wastewater often results in high nutrient loading into aquatic environments, which may lead to favorable conditions for undesirable phytoplankton blooms. Microalgae are efficient in removing nitrogen, phosphorus, and toxic metals from wastewater under controlled environments. If key nutrients in the wastewater stream can be used to grow microalgae for biofuel production, the nutrients can be removed, thus significantly reducing the risk of harmful phytoplankton overgrowth. This review paper summarizes the major nutrient components of different wastewater streams, the mechanisms of algal nutrient uptake, nutrient removal performance of various species of microalgae when cultured in wastewater, and current microalgae production systems. Finally, new algae cultivation technologies applicable for biofuel production and nutrient recovery in polluted water bodies are discussed.

Nutrient recovery from wastewater streams by microalgae: Status and prospects

Azo dyes represent the largest class of industrial colorants. These are no longer used only for the coloration of textiles, plastics, paints, inks, and lacquers, but rather serve as key components in high-tech applications such as optical data storage, reprographics, display devices, dye-sensitized solar cells, energy transfer cascades, light-emitting diodes, laser welding processes, or heat management systems. Azo dyes are also of growing importance in the medical and biomedical fields. In most of these applications, the color is largely irrelevant and it is the ability of the colorants to absorb visible electromagnetic radiation with high efficiency, or other functional property, that is exploited. With the growing awareness and environmental concerns, it is imperative that the hierarchy of reduce, reuse, and degrade be adopted and measures be taken to remove color from the industrial discharge. The present review (a) embodies a comparison of the present decolorization/degradation techniques for water-s...

Removal of Synthetic Textile Dyes From Wastewaters: A Critical Review on Present Treatment Technologies

Dyes may be defined as substances that, when applied to a substrate provide color by a process that alters, at least temporarily, any crystal structure of the colored substances [1,2]. Such substances with considerable coloring capacity are widely employed in the textile, pharmaceutical, food, cosmetics, plastics, photographic and paper industries [3,4]. The dyes can adhere to compatible surfaces by solution, by forming covalent bond or complexes with salts or metals, by physical adsorption or by mechanical retention [1,2]. Dyes are classified according to their application and chemical structure, and are composed of a group of atoms known as chromophores, responsible for the dye color. These chromophore-containing cen‐ ters are based on diverse functional groups, such as azo, anthraquinone, methine, nitro, aril‐ methane, carbonyl and others. In addition, electrons withdrawing or donating substituents so as to generate or intensify the color of the chromophores are denominated as auxo‐ chromes. The most common auxochromes are amine, carboxyl, sulfonate and hydroxyl [5-7].

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Textile Dyes: Dyeing Process and Environmental Impact

Dye sequestration using agricultural wastes as adsorbents

Anaerobic treatment of real textile wastewater with a fluidized bed reactor

In this study, anaerobic treatment of synthetic textile wastewater containing a reactive azo dye, namely, Remazol Brilliant Violet 5R, was investigated. A fluidized bed reactor (FBR) was used in the study. Before the operation period, start-up of the FBR was completed in 128 days with an immobilized microorganism level of 0.069 g volatile suspended solids per g support material (pumice). Anaerobic treatment of synthetic textile wastewater revealed that 300 mg/L dye was removed in the FBR system. Chemical oxygen demand (COD) and color reduction in the system were approximately 60 and 94%, respectively. Under anaerobic conditions, formation of two sulfonated aromatic amines (SAAs) was detected due to anaerobic reduction of the dye. The SAAs were not degraded under anaerobic conditions. In addition to the anaerobic treatment, the effectiveness of aerobic treatment was investigated in order to further reduce the COD after the anaerobic treatment.

S. Sen

Papers

Anaerobic treatment of real textile wastewater with a fluidized bed reactor

Anaerobic Treatment of Synthetic Textile Wastewater Containing a Reactive Azo Dye