Ecotoxicological evaluation of foundry sands and cosmetic sludges using new earthworm biomarkers

Sustainable approaches in concrete production: An in-depth review of waste foundry sand utilization and environmental considerations

This review critically evaluates the potential of Waste Foundry Sand (WFS) as a substitute for fine aggregate in concrete, conducting a comparative analysis of its physical and chemical properties against those of natural sand. The study synthesizes findings from various research experiments to determine concrete's most effective WFS replacement percentage. It compiles and analyzes data on how different WFS ratios affect concrete's mechanical properties, including modulus of elasticity and compressive strength. The review also consolidates research on the impact of WFS on concrete's workability, density, and flowability. A key finding is that WFS, categorized as a non-hazardous waste, possesses a diverse particle size distribution, rendering it suitable for recycling in various industrial applications.The study identifies that a 20%-30% replacement of WFS in concrete significantly improves properties such as voids, specific gravity, and density. However, it is essential to note that exceeding a 30% WFS replacement can result in increased carbonation depth and decreased resistance, primarily due to sulfur trioxide (SO3). Further observations indicate that incorporating higher levels of WFS in self-compacting concrete reduces its flowability and increases water permeability. Moreover, the review highlights the regulatory and classification challenges associated with using WFS, particularly its classification as waste, which hampers its widespread adoption in construction. In conclusion, the study recommends implementing End-of-Waste (EoW) regulations to facilitate sustainable recycling and environmental protection. Additionally, it includes a bibliometric analysis of foundry sand research spanning from 1971 to 2020, providing a comprehensive summary of the field's historical and recent developments.

Reuse or Disposal of Waste Foundry Sand: An Insight into Environmental Aspects

From a circular economy perspective, the recovery and reuse of waste plays a fundamental role. Foundries purchase hundreds of millions of siliceous sands every year to create molds and cores that give shape to the casting. These sands, after several uses, become waste that must be properly recovered or disposed of; they are called waste foundry sands (WFS). The reuse of WFS leads to a reduction in: (i) the consumption of raw materials; (ii) the emissions into the atmosphere; and (iii) the amount of waste sent to landfill—on the other hand, the impact that their use generates on the environment and human health must be carefully assessed. Leaching tests are a fundamental tool for establishing the hazardousness of a waste and its release of contaminants into the environment. This paper presents an analysis of the scientific literature regarding the chemical characteristics of WFS and their release following leaching tests carried out in the laboratory; the environmental standards adopted by the countries that have issued guidelines regarding the reuse of WFS will also be presented.

Assessment of phytotoxicity of leachates from landfilled waste and dust from foundry

The study assesses the contamination, classification and phytotoxicity of foundry waste. The presented results are a part of the research on the agrotechnical use of foundry waste. Landfilled foundry waste (LFW) and dust samples were taken from one of the Polish foundries. An analysis of the waste and its leachate composition was conducted. Phytotoxicity tests were carried out using Lepidium sativum. The aim of the phytotoxicity study was to evaluate germination and root growth after 72 h and the accumulation of heavy metals after 7 days. LFW was least contaminated with heavy metals and metalloids compared to dust. The composition of the foundry dusts depended on the unit of the foundry, from which it was collected. It was found that electric arc furnace dust (EAFD) was the most polluted by heavy metals among the dust samples. According to the requirements of Polish regulations most of tested waste were classified as non-hazardous, and EAFD as hazardous waste due to high Pb concentration in leachate. Phytotoxicity tests have shown a low phytotoxicity of the leachate from most of the tested waste. The results of the accumulation test showed that an excess of metal and metalloids in leachate was not directly related to its accumulation in plants. A negative correlation between EC, Cu, Co, Fe, Pb, Cr, K, Na, sulfate, fluoride, ammonia, phenol and formaldehyde concentration in leachate and GI was found. It was stated that the Fe, Mn, As and Se in plants was significantly correlated with concentrations in leachate.

Correlation of the oxidative stress indices and Cd exposure using a mathematical model in the earthworm, Eisenia fetida

With the increase in heavy metal pollution, it is of great significance to evaluate the ecological security and early warning of cadmium (Cd) contaminated soil. In this paper, a mathematical model was established for the first time by combining the advantages of the factor analysis method and the analytic hierarchy process, and was used to screen and analyze the ecological indices of oxidative stress in earthworms under Cd exposure. The experiment lasted for 40 days, removing one earthworm every 10 days. The Cd²⁺ concentration gradient was set at 0, 1, 10, 20, 100, 200, 400 and 800 mg kg^-1. The ecological indices measured were total protein (TP), peroxidase (POD), superoxide dismutase (SOD), glutathione peroxidase (GPX), glutathione-S-transferase (GST), catalase (CAT), acetylcholinesterase (AChE) and malondialdehyde (MDA) levels. The results showed that when the earthworm was exposed to Cd²⁺ for 10 days and 30 days, in the head tissues, the key indices to focus on for monitoring were both POD. At 20 days and 40 days, the key indices were both TP. For the tail tissue tests, under Cd exposure for 10 days, the key indicator focused on for monitoring was MDA. After 20 days of exposure, the key monitoring indicator was AChE. At 30 days, it was CAT, and at 40 days, it was TP. This study provides a theoretical basis for the prompt, inexpensive, accurate and scientific early warning of metal contaminated soils and establishes a foundation for application of the screening model for other ecological indicators.