Effects of Various Decolorizing Agents on Waste Cotton Fabric Dyed with Reactive Dyes

Shorter fashion cycles have led to the rapid accumulation of unwanted and waste textiles. Compared to light-coloured textiles, the dark-coloured ones are more difficult to recycle and reuse, and their incineration and landfilling have negative environmental consequences. A technology that sufficiently decolorizes these textiles without causing major damage to their structure and properties is therefore useful. In this study, a waste cotton fabric containing vinyl sulfone reactive dyes was subjected to chemical treatments with different oxidants and/or reducing agent. The effects of various treatments on the fabric’s coloration and mechanical properties were compared. The two-step treatment using first Na2S2O4 and then H2O2 showed the best performance, achieving a CIE whiteness index of 65.1, 19.3% tensile strength loss, 1.8% weight loss, 93.5% decolouration rate, and a degree of polymerization of 747.7. A mechanism was proposed to explain the synergistic decolorization process.

Application of Extracellular Polymeric Substances Extracted From Wastewater Sludge for Reactive Dyes Removal

The aim of this study was to investigate the adsorption of three commercial reactive dyes using extracellular polymeric substances (EPS) extracted from the waste sludge of a beer wastewater treatment plant in Hanoi, Vietnam. EPS was extracted from sludge by HCHO-NaOH method and characterized by the measurement of kaolin flocculation activity, dry weight, chemical composition and functional groups. Adsorption of dyes on EPS was conducted by Jartest at different pH, reaction time and EPS dosage. The EPS was composed of 25% of sludge weight. The FTIR analysis showed the present of amine and carboxyl group in the EPS structure. The removal efficiencies of reactive dyes were high at pH below 6, the contact time was from 30 to 60 min and EPS dosage of 200 – 250 mg/L. At optimum condition, the removal efficiency of 85%, 99% and 99% were obtained for Reactive Yellow 176 (RY 176), Reactive Blue 21 (RB 21) and Reactive Red 241 (RR 241), respectively. The adsorption process could be described by both Langmuir and Fruendlich isothermal equations. The maximum dye adsorption capacity for RY 176, RB 21 and RR 241 was 0.50 g/g, 0.72 g/g and 0.95 g/g, respectively. This study revealed that the EPS in wastewater sludge can be utilized as an effective adsorbent for dyes removal, thereby, enhancing the value of sludge in wastewater treatment.

Chitosan and graphene oxide-based nanocomposites for water purification and medical applications: A review

Chitosan (CS) is a natural polysaccharide isolated from insects, molluscs, and fungi. The specific properties of chitosan can be enhanced using physicochemical processes. The composites prepared using CS and graphene oxide (GO) contain active functional groups such as epoxide, carboxyl, and hydroxyl, which possess excellent biocompatibility, high adsorption capacity, and biodegradability. Their low cost and ease of scale-up make them employable for multiple applications in water-treatment plants, electronics, solar cells, and pharmaceuticals. This review provides an overview of sources, types, and properties of chitin, chitosan, and graphene oxide. The use of these composites for the preparation of anti-microbial drugs has been discussed here. The article also explores the applicability of such composites for removal of heavy metals (lead, copper, chromium, cobalt, mercury, etc.), dyes (methylene blue and other reactive dyes), and organic and inorganic contaminants (ofloxacin, naphthanol, phenol, and oil, etc.). The article highlights various knowledge gaps in the field and the scope of future work.

Chitosan and graphene oxide-based nanocomposites for water purification and medical applications: A review

Chitosan (CS) is a natural polysaccharide isolated from insects, molluscs, and fungi. The specific properties of chitosan can be enhanced using physicochemical processes. The composites prepared using CS and graphene oxide (GO) contain active functional groups such as epoxide, carboxyl, and hydroxyl, which possess excellent biocompatibility, high adsorption capacity, and biodegradability. Their low cost and ease of scale-up make them employable for multiple applications in water-treatment plants, electronics, solar cells, and pharmaceuticals. This review provides an overview of sources, types, and properties of chitin, chitosan, and graphene oxide. The use of these composites for the preparation of anti-microbial drugs has been discussed here. The article also explores the applicability of such composites for removal of heavy metals (lead, copper, chromium, cobalt, mercury, etc.), dyes (methylene blue and other reactive dyes), and organic and inorganic contaminants (ofloxacin, naphthanol, phenol, and oil, etc.). The article highlights various knowledge gaps in the field and the scope of future work.