Collection of rich microalgae from textile wastewater and utilized for hydrogen production via hydrothermal gasification route: Performance study

Abstract

In this investigation, textile wastewater was treated in an open raceway pond to promote algae growth for biomass production. Various environmental factors initially hindered the growth of algae. However, the growth rate was improved by integrating titanium dioxide (TiO₂) nanoparticles at different concentrations. The concentrations tested included 0, 2, 4, and 6 % by weight in the wastewater. The study analyzed specific growth rates and biomass production resulting from these variations. Additionally, the cultivated algae were utilized in hydrothermal gasification for hydrogen production. This gasification process was conducted under a residence time of 30 min and a pressure of 200 bar, with gasification temperatures of 350, 450, 550, and 650 °C. Gasification efficiency was further enhanced using a potassium hydroxide (KOH) catalyst. At a higher TiO₂ nanoparticle concentration of 6 %, the specific growth rate and biomass production achieved were approximately 67.9 % and 75.3 %, respectively. In the hydrothermal gasification process, the gasification efficiency (GE), hydrogen selectivity, and higher heating value (HHV) were measured at about 81.5 %, 94.6 %, and 31.5 MJ/Nm³ at 650 °C with the 5 % of KOH catalyst, showing a significant improvement compared to conditions without a catalyst.