Sulfur Dioxide Degradation by Composite Photocatalysts Prepared by Recycled Fine Aggregates and Nanoscale Titanium Dioxide

Xue-Fei Chen; Shi-Cong Kou

doi:10.3390/nano9111533

Sulfur Dioxide Degradation by Composite Photocatalysts Prepared by Recycled Fine Aggregates and Nanoscale Titanium Dioxide

Nanomaterials (Basel). 2019 Oct 29;9(11):1533. doi: 10.3390/nano9111533.

Authors

Xue-Fei Chen^{1

2}, Shi-Cong Kou^{3

4}

Affiliations

¹ School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China. chenxuefei@email.szu.edu.cn.
² College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518000, China. chenxuefei@email.szu.edu.cn.
³ School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, China. kousc@szu.edu.cn.
⁴ College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518000, China. kousc@szu.edu.cn.

Abstract

To alleviate the heavy burden on landfilling, construction and demolition wastes (C&DWs) are recycled and reused as aggregates in cementitious materials. However, the inherent characteristics of recycled fine aggregates (RFA), such as the high crushing index and high-water absorption, magnify the reusing difficulty. Nevertheless, attributing to the high porosity and high level of calcium hydroxides existing in the old mortar, RFA is featured with a high specific surface area and a high alkalinity. These features are useful to augment the total photo-degradation of SO₂ by nano-TiO₂ (NT) intermixed mortar, leading RFA to be an excellent potential carrier to load nano-TiO₂ and prepare the composite photocatalyst. Hence, this study proposed to load NT onto the surface of RFAs and river sands (RSs) (the control) by the soaking method, preparing composite photocatalysts denoted as NT@RFA and NT@RS, respectively. The prepared composite photocatalysts were then utilized as sands in photocatalytic mortar to evaluate for SO₂ degradation. Experiments identified a 50% higher amount of NT was loaded onto the surface of FRA relative to the control. This higher loading amount plus higher alkalinity ultimately translated into a higher photocatalytic activity. In addition, the mortar containing NT@RFA exhibited 46.3% higher physiochemical absorption and 23.9% higher photocatalytic activity than that containing NT@RS. In addition, the durability, embodied by the reuse and anti-abrasive properties, of NT@RFA exceeded that of NT@RS. The overall findings reveal that the NT@RFA not only garners beneficial effect from the high porosity but also generates positive effect from the high alkalinity. Though a number of studies deal with building materials with NT, this study is the first to load NT onto RFA and prepare composite photocatalysts which were then used as fine aggregates in building materials. Consequently, this study proves the potential high-added-value reusability of RFA in green construction materials and provides a low-cost, high-efficiency approach to degrade atmospheric SO₂.

Keywords: SO2 degradation; composite photocatalyst; construction waste; nano-TiO2; photocatalytic mortar; recycled fine aggregate.

Grants and funding

JSGG20160328150149591/Shenzhen Municipal Science and Technology Innovation Council