Sono-electrochemical decolorization and removal COD of Disperse-yellow-7 dye in aqueous solutions

2023-01-04T13:22:19+00:00

The sono-electrochemical decolourization and removal of disperse yellow 7 (DY7, 4-[4-(Phenylazo) phenylazo]-o-cresol) in aqueous solutions was investigated with different concentrations of NaCl and CaCl₂ (0.02, 0.05, 0.1, and 0.2 mol/L) as electrolytes, treatment times, and DY7 concentrations. The combination of electrochemistry (EC) and ultrasound (US) was called the sono-electrochemical (EC_US) process, and it shows a higher treatment efficiency than each parent technique alone. CaCl₂ is more effective than NaCl at the same concentrations. At the dose of DY7 at 25 ppm, the EC_US method (NaCl or CaCl₂ 0.1–0.2 mol/L, frequency 20 kHz, electrodes of TiO₂ and RuO₂-IrO₂-TiO₂) entirely removed the dye from aqueous solutions (100% colour and 100% COD) within a 45 min treatment. This technique could be a valuable alternative for treating dyeing wastewater or other refractory organic compounds in wastewater.

Sustainability of municipal solid waste management: a case study in Hue City, Vietnam

2023-06-17T04:31:57+00:00

The recent expansion and restructuring of Hue City have created numerous opportunities and driving forces to develop the city into a national city of Vietnam. However, it also poses challenges for the local government in many aspects, particularly in municipal solid waste (MSW) management. This paper aims to explore the financial framework of MSW in Hue City, which includes the process of MSW service fee collection and state budget subsidies for MSW management. The cost-revenue analysis using the CORE Plus tool shows that the cost of MSW services in the former Hue City has been significantly subsidized by the state budget, but this subsidy is just sufficient for MSW management, not for improving and upgrading the MSW service system. It was also revealed that although the MSW service fee has been recently increased, the total fee collected and contributed to the state budget from 2018 to 2020 accounted for only 31.2% of the total MSW service cost. The total unit cost, as well as the unit cost of every single MSW service, has reduced over the past five years due to the temporary shutdown of the Thuy Phuong plant, thereby causing disparities in the proportion of each type of service cost over the years. These analysis results were also used for expert consultation to devise a number of solutions that help the city secure its financial viability of MSW services by both preventing the loss of MSW service fees collected from MSW generators and minimizing the collection and transportation costs simultaneously.

Hue University Journal of Science: Earth Science and Environment

Sono-electrochemical decolorization and removal COD of Disperse-yellow-7 dye in aqueous solutions

Sustainability of municipal solid waste management: a case study in Hue City, Vietnam