Current Analytical Chemistry - Online First

Construction and Demolition Waste (CDW) constitutes a major portion of solid waste and presents a significant environmental challenge. This study aims to evaluate the transformation of CDW into a Recycled Aggregate (RA) as a sustainable strategy to mitigate environmental pollution.

The research assesses the mechanical properties and economic benefits of RA concrete, which is made by substituting natural aggregate with RA.

Results indicate that RA has lower density, higher water absorption, and reduced crushing strength compared to natural aggregates. However, RA concrete achieves optimal strength with a 40% replacement rate, marking a critical threshold for material efficiency. An economic analysis confirms the financial viability of using recycled concrete, indicating a favorable investment return. Advances in the research and application of RA suggest its expanding role in engineering applications.

A lifecycle assessment of carbon emissions from concrete production to site transportation was conducted. It revealed that the primary source of emissions in recycled concrete is the raw materials, accounting for about 85% of total emissions. This finding underscores the need to optimize raw material usage to enhance the sustainability of recycled concrete.

Fossil fuels have been used extensively as primary energy sources, which has resulted in nearly depleted reserves, a contaminated environment, and a variety of negative health effects globally. Hydrogen has been proposed by researchers as an effective “carbon neutral” fuel. Large-scale hydrogen production through electrochemical water splitting necessitates the use of inexpensive, extremely effective, and earth-abundant electrocatalysts.

In this study, chitosan–sodium tripolyphosphate (TPP) nanoparticles are combined with CuO nanostructures to produce chitosan–TPP–CuO (CT/CuO) nanocomposite. Chitosan–TPP nanoparticles were first synthesized using the ionic gelation method. These nanoparticles were then extracted, and CuO was synthesized in situ in polymer nanoparticles using a simple chemical precipitation method. Chitosan and CuO are abundantly available and are environmentally beneficial materials. The porous structure and open channels within the chitosan polymer matrix host the CuO nanostructures, which promote electrolyte penetration, mass transport, and charge transfer, while the metal-oxide nanostructures act as catalytic centers. The structural and morphological properties of the CT/CuO nanocomposite were investigated using XRD, HRSEM, and HRTEM. The band gap and functional groups in the material were measured by UV–Vis DRS and FTIR methods, respectively. Elemental analysis was conducted utilizing EDS, HRSEM, and XPS. Thermal characteristics of the CT/CuO nanocomposite were investigated using TG-DTA and DSC methods. Electrochemical techniques were used to investigate the activities of HER and OER.

The XRD examination of the CT/CuO nanocomposite revealed semi-crystalline chitosan peaks and a monoclinic CuO structure. HRSEM and HRTEM pictures indicated that chitosan–TPP nanoparticles and CuO nanostructures were evenly spread and clustered to create a nanoparticulate matrix. UV–Vis DRS indicated that the CT/CuO nanocomposite had a direct band gap of 1.702 eV. The FTIR and XPS studies revealed the various bonds and oxidation states of the nanocomposite. Thermal analyses demonstrated that the inclusion of CuO increased the thermal stability of the CT/CuO nanocomposite. CT/CuO nanocomposite exhibited excellent OER and HER activity, requiring a low overpotential of 444 mV and 379 mV at 10 mA cm⁻² and -10 mA cm⁻², respectively.

Biopolymer metal-oxide nanocomposites could potentially be used as electrocatalysts in water splitting, energy conversion, storage devices, sensors, and several other fields.

This study presented new sensitive and selective modified carbon paste (MCPE) potentiometric sensors modified with different ion pairs for the determination of the antihypertensive drug diltiazem hydrochloride (DTM-HCl) in biological fluids, pharmaceutical preparations, and in its pure form.

Plasticizers, ion pair type, ion pair content, response time, temperature, and pH were just a few of the experimental factors evaluated that were found to affect electrode efficiency. The two electrodes that show the best sensitivity were prepared by mixing diltiazem-tetraphenyl borate (DTM-TPB) ion pair, graphite, and TCP or o-NPOE as a plasticizer.

Over the concentration ranges of 1.0x10^-5–1.0x10^-2, the produced electrodes I and II demonstrated monovalent Nernstian responses of 55.7±0.902 and 57.6±0.451 mV decade^-1. The selectivity property of the suggested electrodes was used to study the interference ions. The concentration of DTM-HCl in pharmaceutical formulations and biological fluids was measured using these modified electrodes. During the validation procedure, metrics like linearity, accuracy, precision, limit of detection, limit of quantification, and specificity were used.

The obtained results showed good agreement with the HPLC technique as indicated by the F and t-test values and can conclude the possibility of using this potentiometric method in the routine analysis of DTM-HCl.