We report a comprehensive quantitative study of the production of refined bio-crudes via a controlled hydrothermal liquefaction (HTL) process using Ulva fasciata macroalgae (UFMA) as biomass and ultrananocrystalline Fe ₃ O ₄ (UNCFO) as catalyst.

Among several Puerto Rican algae, Sargassum sp. (SG) and Chaetomorpha (CM) showed the highest phenol adsorption capacity from aqueous solutions and were used in optimized adsorption batch experiments at room temperature. The effects of pH, adsorbent dose, phenol concentration, salinity and presence of interfering substances were evaluated. Initial solution pH exhibited a strong effect, mainly on the phenol aqueous chemistry; showing the maximum adsorption at pH 10. Sorption isotherm results were modelled according to the Langmuir, Tempkin and Freundlich equations. Isotherm modelling indicated a maximum adsorption capacity (q_max) of 82.10 and 17.7 mg of phenol per gram of SG and CM, respectively. Salinity and presence of detergent in the matrix solution showed a positive effect on the adsorption, suggesting that adsorption of phenol was mostly driven by polar forces and not by ionic exchange. On the other hand, presence of heavy metals like copper, lead and cobalt had a negative effect on the adsorption. According to these results, the potential formation of hydrogen bonds between the algae and phenol is proposed as the main adsorption mechanism. These results provide further insight into the adsorption mechanism of phenol and their use as inexpensive adsorbents for the treatment of phenol-containing wastewaters.

This study addresses the persistent challenge of polysulfide dissolution in lithium–sulfur (Li–S) batteries by introducing magnesium oxide (MgO) nanoparticles as a novel additive. MgO was integrated with sulfur using a scalable process involving solid-state melt diffusion treatment followed by planetary ball milling. XRD measurements confirmed that sulfur (S₈) retains its orthorhombic crystalline structure (space group $F_{ddd}$) following the MgO incorporation, with minimal peak shifts indicating slight lattice distortion, while the increased peak intensity suggests enhanced crystallinity due to MgO acting as a nucleation site. Additionally, Raman spectroscopy demonstrated sulfur’s characteristic vibrational modes consistent with group theory (point group $D_{2}h$) and highlighted multiwalled carbon nanotube (MWCNT′s) D, G, and 2D bands, with a low I_D/I_G ratio (0.47), which indicated low defects and high crystallinity in the prepared cathode. The S–MgO composite cathode exhibited superior electrochemical behavior, with an initial discharge capacity (950 mA h g⁻¹ at 0.1 C), significantly improved compared to pristine sulfur’s. The presence of MgO effectively mitigated the polysulfide shuttle effect by trapping polysulfides, leading to enhanced stability over 400 cycles and the consistent coulombic efficiency of over 99.5%. After 400 cycles, EDS and SEM analyses confirmed the structural integrity of the electrode, with only minor fractures and slight sulfur content loss. Electrochemical impedance spectroscopy further confirmed the enhanced performance.

Sulfur holds immense promise for battery applications owing to its abundant availability, low cost, and high capacity. Currently, sulfur is commonly combined with alkali or alkaline earth metals in metal-sulfur batteries. However, these batteries universally face challenges in cycling stability due to the inevitable issue of polysulfide dissolution and shuttling. Additionally, the inferior stability of metal sulfide discharge compounds results in low S⁰/S^2- redox potentials (<-0.41 V vs SHE). Herein, we leverage the principle of the hard-soft acid-base theory to introduce a novel silver-sulfur (Ag-S) battery system, which operates on the reaction between the soft acid of Ag⁺ and the soft base of S^2-. Due to their high reaction affinity, the discharge compound of silver sulfide (Ag₂S) is intrinsically insoluble and fundamentally stable. This not only resolves the polysulfide dissolution issue but also leads to a predominantly high S⁰/S^2- redox potential (+1.0 V vs. SHE). We thus exploit the Ag-S reaction for a primary zinc battery application, which exhibits a high capacity of ∼620 mAh g^-1 and a high voltage of ∼1.45 V. This work offers valuable insights into the application of classic chemistry theories in the development of innovative energy storage devices.