Abstract
Azo dyes are very resistant to light-induced fading and biodegradation. Existing advanced oxidative pre-treatment methods based on the generation of non-selective radicals cannot efficiently remove these dyes from wastewater streams, and post-treatment oxidative dye removal is problematic because it may leave many byproducts with unknown toxicity profiles in the outgoing water, or cause expensive complete mineralization. These problems could potentially be overcome by combining photocatalysis and biodegradation. A novel visible-light-responsive hybrid dye removal agent featuring both photocatalysts (g-C3N4-P25) and photosynthetic bacteria encapsulated in calcium alginate beads was prepared by self-assembly. This system achieved a removal efficiency of 94% for the dye reactive brilliant red X-3b and also reduced the COD of synthetic wastewater samples by 84.7%, successfully decolorized synthetic dye-contaminated wastewater and reduced its COD, demonstrating the advantages of combining photocatalysis and biocatalysis for wastewater purification. The composite apparently degrades X-3b by initially converting the dye into aniline and phenol derivatives whose aryl moieties are then attacked by free radicals to form alkyl derivatives, preventing the accumulation of aromatic hydrocarbons that might suppress microbial activity. These alkyl intermediates are finally degraded by the photosynthetic bacteria.
Highlights
These wastewaters pose substantial environmental hazards due to their strong colors, high Chemical Oxygen Demand (COD) and the complex chemical composition of the discharged effluent [2,3,4]
All the typical X-ray diffraction (XRD) peaks of P25 and pure g-C3N4 are present in the spectrum of hybrid gC3N4-P25
The photocatalytic properties of g-C3N4-P25 were evaluated by monitoring the degradation of the azo dye reactive brilliant red X-3b and comparing the rates of degradation achieved with
Summary
Large amounts of dye-containing wastewaters are generated during processes involved in the manufacture, utilization ( by textile, paper, and carpet industries), and disposal of dyes [1]. These wastewaters pose substantial environmental hazards due to their strong colors, high COD 20% of which is due to dyes and 80% to auxiliary dyeing agents such as sodium acetate and starch) and the complex chemical composition of the discharged effluent [2,3,4]. To avoid environmental problems there is a clear need to treat dye-containing wastewater. Degradation of dye-containing wastewater by a novel hybrid composite design, data collection and analysis, decision to publish, or preparation of the manuscript
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