The textile wastewaters have a diverse composition depending both on the used raw materials and applied manufacturing technologies. These wastewaters may contain various pollutants such as organic compounds (e.g. residual dyes), suspended solids, metal ions etc. Most of dyes are synthetic compounds with aromatic molecular structures and non-biodegradable. The oxidative destruction via homogenous oxidation processes with hydrogen peroxide (simple chemical oxidation with H 2 O 2 or advanced oxidation processes (AOPs) as Fenton oxidation, ozonation, photo-oxidation and photo-Fenton oxidation etc.) are attractive alternatives to conventional treatments, easy to be applied and not so expensive. The use of H 2 O 2 in AOPs has the advantage that the decomposition products of organic pollutants are common harmless compounds. Moreover, H 2 O 2 decomposes itself in water and oxygen. This paper is a review of authors' researches regarding homogenous oxidation with hydrogen peroxide applied for different types of textile dyes in order to perform high textile dye removals considering some relevant factors: pH, agitation regime, temperature, H 2 O 2 concentration, textile dye concentration, oxidation time, ferrous or metallic ions concentration, etc.
The environmental issues associated with residual colour in treated textile effluents are always a concern for each textile operator that directly discharges, both sewage treatment works and commercial textile operations, in terms of respecting the colour requirements. This paper aims to help a textile operator to decide on options available to plan forward strategy that will ensure compliance with the environmental regulators' requirements on a progressive basis. To achieve this objective the paper is structured in order to present various options and solutions that are explained and developed mainly based on different physico-chemical treatment steps (i.e. adsorption using different unconventional adsorptive materials as 'low cost' adsorbents of coal ashes, sawdust wastes, peat and comparisons with a classic commercial 'activated carbon'; catalysed chemical oxidation with hydrogen peroxide; coagulation-flocculation with iron salts and organic polyelectrolyte) integrated into a specific order in the wastewater technological treatment process for decolorization or large-scale colour removal processes of textile effluents produced into a private Northern Romanian textile plant. The influence of different operating parameters (i.e. pH, material or chemical reagent concentration, temperature, operational time, agitation and operational working regime) is discussed together with the textile effluent treatment efficiency obtained for each studied influencing parameters (the best solutions for each parameters are in view and discussed). These technical and operational treatment solutions are both threats and opportunities for the textile operator, and the best colour removal option is obtained from combination of technologies or proposed treatment steps rather than from one single-stage process.
The use of biosorbents for the decontamination of industrial effluent (e.g., wastewater treatment) by retaining non-biodegradable pollutants (antibiotics, dyes, and heavy metals) has been investigated in order to develop inexpensive and effective techniques. The exacerbated water pollution crisis is a huge threat to the global economy, especially in association with the rapid development of industry; thus, the sustainable reuse of different treated water resources has become a worldwide necessity. This review investigates the use of different natural (living and non-living) microbial biomass types containing polysaccharides, proteins, and lipids (natural polymers) as biosorbents in free and immobilized forms. Microbial biomass immobilization performed by using polymeric support (i.e., polysaccharides) would ensure the production of efficient biosorbents, with good mechanical resistance and easy separation ability, utilized in different effluents’ depollution. Biomass-based biosorbents, due to their outstanding biosorption abilities and good efficiency for effluent treatment (concentrated or diluted solutions of residuals/contaminants), need to be used in industrial environmental applications, to improve environmental sustainability of the economic activities. This review presents the most recent advances related the main polymers such as polysaccharides and microbial cells used for biosorbents production; a detailed analysis of the biosorption capability of algal, bacterial and fungal biomass; as well as a series of specific applications for retaining metal ions and organic dyes. Even if biosorption offers many advantages, the complexity of operation increased by the presence of multiple pollutants in real wastewater combined with insufficient knowledge on desorption and regeneration capacity of biosorbents (mostly used in laboratory scale) requires more large-scale biosorption experiments in order to adequately choose a type of biomass but also a polymeric support for an efficient treatment process.
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