Development of Linear Fresnel Photocatalytic Systems for Water Purification and Microalgae Biorefinery under Sunlight

概要

In the past few decades, water pollution, energy crisis and food shortage have become obstacles to
the sustainable development of the world. Recently, solar-light-driven photocatalysis has received
extensive attention as a stable, environmentally friendly and cost-effective technology. Under the
irradiation of clean and eternal sunlight, it could effectively decompose the organic pollutants such as
organic dyes, antibiotics and pathogenic bacteria in water bodies. In addition, microalgae, as an arable
land-saving, fast-growing biological resource, could also be decomposed by photocatalysis to carry out
the biorefinery for generating carbohydrate, protein and lipid. The generated carbohydrate, protein and
lipid could be further employed to produce green energy (e.g., hydrogen, biofuel) and animal feed.
Therefore, solar-light-driven photocatalysis has great potential to purify water bodies and alleviate
energy crisis and food shortage. To realize high-efficiency photocatalytic water purification and
microalgae biorefinery, suitable light irradiance and reaction temperature are required. However, due to
the changes in the solar position and variable weather conditions, the development of photocatalytic
system for providing optimized solar light and temperature for realizing high-efficiency photocatalytic
reaction is still a challenge. Linear Fresnel (LF) is a solar concentrator with several columns of mirrors
and is traditionally used to focus ultra-high solar energy. However, for high-efficiency photocatalytic
reaction, optimal irradiance and temperature need to be pursued. If LF has suitable number of mirrors
that can be controlled according to solar motion and weather, it is possible to control solar energy for
providing the optimized light irradiance and temperature. According to our best knowledge, no LF has
been modified and applied for high-efficiency photocatalytic water purification and microalgae
biorefinery.
In addition, to utilize LF in photocatalytic reaction, photocatalyst needs to be equipped in LF.
However, traditional photocatalyst powder may lead to complex post-separation and high cost, which is
not suitable for practical application. Therefore, to facilitate practical photocatalytic water purification
and microalgae biorefinery, immobilized photocatalyst is required. For non-suspended water
purification, photocatalytic immobilized beads could be the suitable option. However, for microalgae
biorefinery, since the algal fluid appears as a suspension, this may lead to cell deposition and system
clogging. To make algal cells fully in contact with the immobilized photocatalyst while cause no system
blockage, suitable photocatalytic carriers need to be considered. ...