Accurately quantifying the detoxication of solid waste and its scientific insights: The case of typical industrial waste

Abstract

<p indent="0mm">The increasing surge in solid waste generation poses tremendous risks to the safety of the environment, resources, and industry, prompting solid waste management to be a global environmental issue and a grand challenge in the 21st century. Solid waste has a double attribute of resource and environment, which is commonly resolved by recycling and detoxication. Previously, the resource attribute of solid waste was measured with recyclability. To achieve the sound management of solid waste, its environmental attribute discovery plays a crucial role in process selecting and policy formulating, especially for some hazardous industrial waste. In this study, we first proposed the removability concept to indicate the environmental attribute, and then established an environmental attribute measuring method, utilizing an interdisciplinary philosophy of statistical entropy and pollution grade. By measuring the removability of toxic substances towards detoxication, the method determines the potential and difficulty of toxic substance removal and resource recovery under current process conditions. Applying the method, we evaluated the removability of various toxic substances in 24 types of industrial waste. A sensitivity analysis was also picked up to identify the key influencing factors. Finally, we analyzed the feasibility of removing toxic substances from industrial waste by recovery technologies. The research on heavy metals and inorganic non-metallic toxic substances in industrial waste shows that the removability of these toxic substances is correlated with valence and stability. The results range from 11 bit^–1 to 66 bit^–1, revealing a low removability of the above toxic substances. However, the removability of organic toxic substances is related to their degradability. Besides, the combination of heavy metals and organic toxic substances could further decrease the removability of the toxic substances. The sensitivity analysis assessed the influence of different factors on the removability of toxic substances. The results suggest that the component, stability, and concentration of toxic substances have obvious effects on removability. To be specific, lower stability will reduce the difficulty to enrich and remove toxic substances. Thus, the high stability of the toxic substances in industrial waste emphasizes the requirement of an additional energy supply to change the phase composition or valence state of the toxic substances. However, the improvement of removability has an efficiency limit, with the critical value of the limit relating to the initial removability. Compared to virgin mining, the removability of over 50% of toxic substances in industrial waste fails to meet the requirements under the condition of the lowest industrial grade. Meanwhile, the feasibility of toxic substance removal and resource recovery in industrial waste detoxication should take both the types of waste and toxic substances into account. From the perspective of waste, only 6 types of industrial waste among 24 types of industrial waste being studied have a removal index greater than zero, including gold tailings, steel slag, and fly ash. Hence, it is suitable to enable toxic substance removal and impair the environmental attribute by material recovery when treating these 6 types of waste. In contrast, the rest types of industrial waste are of high environmental attributes, making it hard to remove the toxic substances by recovery due to the inferior removability and economic feasibility under the current technological condition. From the perspective of toxic substances, the slight differences of toxic substances in industrial wastes make it difficult to perform targeted separation and precise removal with the same technology. In a conclusion, removability is an intrinsic property of solid waste that can influence extrinsic properties, such as the environmental risk of solid waste sound management. Therefore, we considered incorporating the environmental attribute into the classification of solid waste and carried out the complete process of detoxification and accurate accounting. It will assist the recycling industry in the design of waste treatment and resource recycling, and guide the upgrading of waste disposal technology.