The critical properties of La_0.8Ca_0.2Mn_1−xCo_xO₃ (x = 0, 0.1, 0.2 and 0.3) compounds were investigated by analysis of the magnetic measurements in the vicinity of their critical temperature. Arrott plots revealed that the paramagnetic PM-ferromagnetic (FM) phase transition for the sample with x = 0 is a first order transition, while it is a second order transition for all doped compounds. The critical exponents β, γ and δ were evaluated using modified Arrott plots (MAP) and the Kouvel-Fisher method (KF). The reliability of the evaluated critical exponents was confirmed by the Widom scaling relation and the universal scaling hypothesis. The values of the critical exponents for the doped compounds were consistent with the 3D-Heisenberg model for magnetic interactions. For x = 0.1, the estimated critical components are found inconsistent with any known universality class. In addition, the local exponent n was determined from the magnetic entropy change and found to be sensitive to the magnetic field in the entire studied temperature range.

A method for the measurement of total mercury (T-Hg) in environmental samples using cold vapour atomic absorption spectrometry (CV AAS) has been validated yielding a dynamic range (0.04–10.00 μg/kg) and high certified reference material (CRM) recovery (>90%). The validation was carried out according to International Union of Pure and Applied Chemistry (IUPAC) validation and Eurachem Guides. A freeze-dried and homogenised sample was weighed and then digested using Suprapur acids (HNO₃, H₂SO₄, and HF) with potassium dichromate solution in a hot block digestion system. A calibration curve was constructed (R² > 0.999). Two CRMs (Marine Sediment Reference Material (PACS-3) and Trace Elements in Muscle Tissue (Trace Elements and Methylmercury in Mussel Tissue (NIST2976)) were utilised for quality assurance and control. The limit of quantification (LOQ) calculated as 0.04 µg/kg, and uncertainty (U) calculated as 2%. The obtained results showed the suitability of this method for direct mercury measurement in environmental samples. Additionally, the proficiency of this method was recognised by accreditation under the standard of International Organization for Standardization (ISO/IEC 17025:2017) for competence of testing and calibration laboratories.

Chemical wastewater treatment in laboratories poses a significant challenge due to the complex nature of the contaminants involved. Humic materials and clay have emerged as promising solutions for remediation due to their unique properties, such as high adsorption capacity and ability to form stable complexes with heavy metals. This research explores the potential of humic materials and clay in wastewater treatment by evaluating their effectiveness in removing various chemicals commonly found in laboratory effluents. Ultimately, this research aims to contribute to developing sustainable and cost-effective approaches for managing chemical wastewater in laboratories. Humic acid demonstrated a higher affinity for specific metals, with Cobalt (Co) showing the highest uptake, followed by Manganese (Mn) and Molybdenum (Mo), among other elements. On the other hand, the natural clay sample exhibited a different uptake sequence, indicating its distinct sorption preferences for various metals. The notable uptake of Molybdenum (Mo), Barium (Ba), and Arsenic (As) by the clay sample underscores its potential as an effective sorbent for these elements in wastewater treatment applications.