Mohamed A. Hassan

Water scarcity and contamination demand efficient wastewater treatment technologies that are both effective and sustainable. In this study, a waste‑derived zeolite/hydroxyapatite nanocomposite (W‑ZEO/HAP‑NC) was synthesized from rice‑husk‑derived silica and aluminum‑can waste and evaluated for its versatile, dual-functional capacity to remove both Cd(II) and malachite green (MG) from water. XRD, SEM–EDX, FTIR, zeta potential and BET analyses confirmed a porous W‑ZEO/HAP‑NC framework enriched with hydroxyl, phosphate, and silicate groups that supply abundant adsorption sites. Batch experiments showed rapid, pH‑dependent uptake, with equilibrium and kinetic data best described by the Freundlich and pseudo‑second‑order models. Under optimized conditions, W‑ZEO/HAP‑NC achieved Langmuir capacities of 666.7 mg g ^− 1 for Cd(II) and 400.0 mg g ^− 1 for MG, driven by electrostatic attraction, ion exchange, surface complexation, π–π interactions, and hydrogen bonding. The composite retained 85–95% of its initial efficiency after four adsorption–desorption cycles, underscoring its potential as a high‑capacity, regenerable adsorbent for wastewater purification and waste valorization.

Sandy calcareous soils in arid regions suffer from low phosphorus (P) availability due to high fixation rates, limiting crop productivity. This study investigates a novel hybrid smart fertilizer (BN) composed of olive pomace biochar (BC) and nano-hydroxyapatite (nHAP). BN was synthesized and characterized using XRD, FTIR, SEM/TEM, and zeta potential analysis. Its P release kinetics were modeled, and its agronomic performance was assessed on faba bean (Vicia faba L.) in a pot experiment under sandy soil conditions with and without wood vinegar (WV). The 1:1 BC:nHAP formulation showed a two-stage release profile: a rapid initial burst (Higuchi model, R² = 0.86) followed by sustained zero-order release (R² = 0.80). In the pot experiment, BN combined with WV significantly increased plant height by 36%, shoot fresh weight by 232%, and available soil P by 39% compared to conventional SSP (p < 0.05). This synergistic treatment also improved root nodulation and nutrient (N, P, K) uptake. The BC-nHAP hybrid coupled with WV acts as an efficient P delivery system, improving soil fertility in arid environments based on circular economy principles, aligning with SDGs 2, 12, and 15.

Commercial Pt/C anodes of direct formic acid fuel cells (DFAFCs) get rapidly poisoned by in-situ generated CO intermediates from formic acid non-faradaic dissociation. We succeeded in increasing the Pt nanoparticles (PtNPs) stability and activity for formic acid oxidation (DFAFCs anodic reaction) by embedding them inside a chitosan matrix obtained from seafood wastes. Atop the commercial Pt/C, formic acid (FA) is predominantly oxidized via the undesired poisoning dehydration pathway (14 times higher than the desired dehydrogenation route), wherein FA is non-faradaically dissociated to CO resulting in deactivation of the majority of the Pt active-surface sites. Surprisingly, PtNPs chemical insertion inside a chitosan matrix enhanced their efficiency for FA oxidation significantly, as demonstrated by their 27 times higher stability along with ~400 mV negative shift of the FA oxidation onset potential together with 270 times higher CO poisoning-tolerance compared to that of the commercial Pt/C. These substantial performance enhancements are believed to originate from the interaction of chitosan functionalities (e.g., NH₂ and OH) with both PtNPs and FA molecules improving FA adsorption and preventing the PtNPs aggregation, besides providing the required oxygen helping with the oxidative removal of the adsorbed poisoning CO-like species at low potentials. Additionally, chitosan induced the retrieval of the Pt surface-active sites by capturing the in-situ formed poisoning CO intermediates via a so-called “migration mechanism”.