Environmental Geochemistry of Cadmium in Coal Mining Area and Environmental Application of Heavy Metals in Photocatalysis

煤礦區中鎘的環境地球化學及重金屬在光催化的作用研究

Student thesis: Doctoral Thesis

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Detail(s)

Awarding Institution
Supervisors/Advisors
  • T C LAU (Supervisor)
  • Guijian Liu (External person) (External Supervisor)
Award date4 Jun 2018

Abstract

Cadmium (Cd) has attracted much attention due to its potential toxicity. Cadmium and its compounds may be released into the environment during coal utilization, and thereby impact human health through the food chain. This thesis presents a systematic study on the abundance, distribution patterns, modes of occurrence, and environmental impacts of Cd in coal mining areas and applications of heavy metal in the environment.

The main findings of this research were as follows: (1) We estimated Cd concentration in Chinese coals taking coal reserves as the weighting factor; the results showed the average Cd abundance in Chinese coals is 0.25 mg/kg. The abundance of Cd in coal varies according to the coal-forming period and coal rank. Coal-producing provinces may be divided into high-Cd district, medium-Cd district and low-Cd district according to the average Cd abundances. (2) Coal samples from different coalfields in China were collected and analyzed to investigate the modes of occurrence of Cd. By performing sequential chemical extraction, results showed that coal Cd content is mainly associated with carbonate, silicate and sulfide minerals. (3) We investigated the spatial and temporal distribution characteristics of Cd from coal combustion in China for nearly 20 consecutive years. The results showed that pollution control measures have effectively limited the emissions of Cd in China, and the uncertainties in the estimation of Cd emissions from coal combustion in China can be ascribed to coal Cd concentration, as well as removal efficiency and share of air pollution control devices. (4)We investigated the environmental geochemical behaviors of Cd in the supergene environment of a mining area taking Huaibei coal mining area as an example, and further conducted the environmental risk assessment of Cd pollution. The results showed a high percentage of phyto-available Cd concentration in soils around coal this mining area. Four ecological evaluation models revealed a moderate risk of Cd in soils in our study areas. (5) A Co-based complex was used as photocatalysts to study the photocatalytic CO2 reduction performance. With Ru(bpy)3Cl2 as a photosensitizer, CO with the TON of 2660 and selectivity of 98% was obtained. With a cheap and commercially available organic dye purpurin as a photosensitizer, CO with a TON as high as 790 and selectivity of 100% can be achieved.

    Research areas

  • Cadmium, Environmental geochemistry, Coal mining area, Environmental application, Photocatalysis