Development of a leaching procedure to assess the risk of uranium leaching due to construction and demolition waste disposal

Radiological Characteristics of Carbonated Portland Cement Mortars Made with GGBFS

The objective of this study is to assess whether the carbonation process can modify the physicochemical characteristics of the natural radionuclides of the three natural radioactive series, together with ⁴⁰K. Three mortar specimens with different percentages of ground granulated blast-furnace slag (GGBFS), cured under water for 1, 3, 7, 14, or 28 days, were subjected to a natural carbonation process. Activity concentrations for the solid and ground mortars were determined by gamma spectrometry and by radiochemical separation of isotopic uranium. The novelty of this paper relies principally on the study we have carried out, for the first time, of the radiological characteristics of carbonated Portland cement mortars. It was found that the chemical properties of the 3 mortar specimens were not affected by the carbonation process, with particular attention placed on uranium (²³⁸U, ²³⁵U, and ²³⁴U), the activity concentrations of which were equivalent to the ²²⁶Ra results and ranged from 5.5 ± 1.6 Bq kg⁻¹ to 21.4 ± 1.2 Bq kg⁻¹ for the ²³⁸U. The average activity concentrations for the 3 types of mortars were lower than 20.1 Bq kg⁻¹, 14.5 Bq kg⁻¹, and 120.2 Bq kg⁻¹ for the ²²⁶Ra, ²³²Th (²¹²Pb), and ⁴⁰K, respectively. Annual effective dose rates were equivalent to the natural background of 0.024 mSv. In addition, it was observed that the variation rate for the ²²²Rn emanation was due primarily to the Portland cement hydration and not due to the pore size redistribution as a consequence of the carbonation process. This research will provide new insights into the potential radiological risk from carbonated cement-based materials. Moreover, the assessment that is presented in this study will convey valuable information for future research that will explore the activity concentration of building materials containing NORM materials.

Chemicals of concern in construction and demolition waste fine residues: A systematic literature review

Despite the increasing use of chemical additives in construction and their potential threat to the environment and human health, many C&DW studies lack a comprehensive view of chemicals of concern (COC) in C&DW. This study systematically reviewed published studies from 2010 to August 2021 using a keyword search methodology to explore COC in C&DW fine residues based on 73 articles identified from 5 prominent databases. Results show that trace/heavy metals (As, Cr, Cu, Cd, and Pb) as well as high concentrations of toxic gasses (methane, hydrogen sulphide and mercury vapour) have been reported in landfills. Besides, organic chemicals such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and brominated flame retardants have been found in landfill leachates in the Netherlands and widely detected in landfill leachates in Sweden, Japan, and Canada. The potential of these contaminants to cause health complications has also been reported. Carcinogenicity, liver and kidney damage, cumulative damage, neurological disorders and foetal damage were reported as associated health implications of exposure to COC from C&DW. A waste disposal lens was used to explore the factors that influence the environment and human health impacts (pH, gypsum and organic content, size fraction, atmospheric exposure and liquid infiltration rate). Despite environmental and health issues relating to C&DW fine residues, the ultimate destination for C&DW fine residues remains in general landfills. Although significant efforts in managing C&DW have been implemented at various levels, those specifically targeting C&DW fine residues remain sparse.

Adsorption of uranium from its aqueous solutions using activated cellulose and silica grafted cellulose

The present work provides a thorough description of the preparation of two cellulose anion exchange resins. In addition, the application of the prepared resins for treatment the uranium-contaminated wastewater. In the preparation, the first resin was cellulose reacted with 0.3 M HNO3 to produce Activated Cellulose (AC), while the second was AC treated with sodium metasilicate and phosphoric acid to yield Silica Grafted Cellulose (SGC). The efficiency of the two prepared resins for uranium adsorption from aqueous solution was testifying on a batch scale. In solutions of pH ranging from 4 to 7, results showed a high exchange rate and uptaking capacity up to 105 mg/g. However, the addition of NO3 −, Fe3+ and Th4+ ions to the target media has an adverse impact on the uranium sorption for AC adsorbent. Otherwise, the addition of uranyl sulfate complexes could ameliorate Fe3+ and Th4+ adsorbed into the SGC.

Characterizing the paper industry sludge for environmentally-safe disposal

The world paper industry produces a great amount of industrial solid waste that undergoes a treatment process that can be either primary, secondary, or tertiary, in order to adapt the waste for correct disposal. The paper manufacturing industries search for the best way to dispose of their wastes, generally in landfills, but there are few studies proving the effectiveness of such measure from the environmental, technological and economic points of view. Knowing the characteristics of this waste and understanding the treatment process it is submitted to are fundamental issues to manage it and comply with environmental demands. The purpose of this paper is to perform a chemical, mineralogical, thermal, morphological, physical and environmental characterization of the paper and pulp industry wastes, in order to assess alternatives for their adequate disposal, such as controlled landfills, sanitation, incineration, and sea dumping. It was observed that the material presents physical, chemical, and morphological features that indicate the possibility of reusing it in other production chains, such as the ceramic industry, besides being classified as non-hazardous wastes. Furthermore, disposal in sanitary landfills presents advantages in environmental and technological terms.