Heavy metal toxicity has demonstrated to be a crucial issue for environment and human health. There has been an increasing ecological and global public health concern related with environmental contamination by these metals. For these reasons, a considerable attention has been paid to design efficient materials for heavy metal removal. This article offers a solution to develop a green adsorbent based on Chitosan Microspheres/Sodium Alginate hybrid beads (CSM/SA) for metal ion elimination from aqueous solutions. The efficiency of this eco-friendly material was divulged using kinetic study for Cr(VI) and Pb(II) removal. Properties of the obtained hybrid beads were improved by correlation between original chitosan microspheres and sodium alginate. Moreover, at different metal concentration, pH solution and contact time, the beads were evaluated in discharged batch operations from Pb(II) and Cr(VI). The maximum adsorption capacity was 180 mg g^− 1 for Pb(II) and 16 mg g^− 1 for Cr(VI). The adsorption kinetics were evaluated using pseudo-first and pseudo-second rate models. Adsorption isotherms were simulated by Langmuir and Freundlich models. This study indicates that the CSM/SA hybrid beads could be developed into a very sustainable technology for highly effective elimination of metal ions from wastewater.

Ba_0.85Ca_0.15Zr_0.10Ti_0.90O₃ (BCZT) relaxor ferroelectric ceramics exhibit enhanced energy storage and electrocaloric performances due to their excellent dielectric and ferroelectric properties. In this study, the temperature-dependence of the structural and dielectric properties, as well as the field and temperature-dependence of the energy storage and the electrocaloric properties in BCZT ceramics elaborated at low-temperature hydrothermal processing are investigated. X-ray diffraction and Raman spectroscopy results confirmed the ferroelectric–paraelectric phase transition in the BCZT ceramic. At room temperature and 1 kHz, the dielectric constant and dielectric loss reached 5000 and 0.029, respectively. The BCZT ceramic showed a large recovered energy density (W_rec) of 414.1 mJ cm⁻³ at 380 K, with an energy efficiency of 78.6%, and high thermal-stability of W_rec of 3.9% in the temperature range of 340–400 K. The electrocaloric effect in BCZT was explored via an indirect approach following the Maxwell relation at 60 kV cm⁻¹. The significant electrocaloric temperature change of 1.479 K at 367 K, a broad temperature span of 87 K, an enhanced refrigerant capacity of 140.33 J kg⁻¹, and a high coefficient of performance of 6.12 obtained at 60 kV cm⁻¹ make BCZT ceramics potentially useful coolant materials in the development of future eco-friendly solid-state refrigeration technology.

The lead-free Ba_0.85Ca_0.15Zr_0.10Ti_0.90O₃ (BCZT) relaxor ferroelectric ceramic has aroused much attention due to its enhanced piezoelectric, energy storage and electrocaloric properties. In this study, the BCZT ceramic was elaborated by the solid-state reaction route, and the temperature-dependence of the structural, electrical, piezoelectric, energy storage and electrocaloric properties was investigated. X-ray diffraction analysis revealed a pure perovskite phase, and the temperature-dependence of Raman spectroscopy, dielectric and ferroelectric measurements revealed the phase transitions in the BCZT ceramic. At room temperature, the strain and the large-signal piezoelectric coefficient reached a maximum of 0.062% and 234 pm V⁻¹, respectively. Furthermore, enhanced recovered energy density (W_rec = 62 mJ cm⁻³) and high-energy storage efficiency (η) of 72.9% at 130 °C were found. The BCZT ceramic demonstrated excellent thermal stability of the energy storage variation (ESV), less than ±5.5% in the temperature range of 30–100 °C compared to other lead-free ceramics. The electrocaloric response in the BCZT ceramic was explored via the indirect approach by using the Maxwell relation. Significant electrocaloric temperature change (ΔT) of 0.57 K over a broad temperature span (T_span = 70 °C) and enhanced coefficient of performance (COP = 11) were obtained under 25 kV cm⁻¹. The obtained results make the BCZT ceramic a suitable eco-friendly material for energy storage and solid-state electrocaloric cooling devices.