Study on adsorption behavior of humic acid on aluminum in Enteromorpha prolifera.

High level of aluminum content in Enteromorpha prolifera posed a growing threat to both its growth and human health. This study focused on exploring the factors, impacts, and process of removing aluminum from Enteromorpha prolifera using humic acid. The results showed that under experimental conditions of 0.0330 g·L-1 humic acid concentration, pH 3.80, 34 °C, and a duration of 40 min, the removal rate was up to 80.18%. The levels of major flavor components, proteins, and amino acids in Enteromorpha prolifera increased significantly after treatment, while polysaccharides and trace elements like calcium and magnesium decreased significantly. Infrared spectroscopy demonstrated that the main functional groups involved in binding with Al3+ during humic acid adsorption were hydroxyl, carboxyl, phenol, and other oxygen-containing groups. The adsorption process of Al3+ by humic acid was a spontaneous phenomenon divided into three key stages: fast adsorption, slow adsorption, and adsorption equilibrium, which resulted from both physical and chemical adsorption effects. This study provided a safe and efficient method in algae metal removal.

Impact of modification on the properties of Eucheuma biochar and its adsorption of phenanthrene from aqueous solution.

Biochar was derived from Eucheuma (EBC) at a temperature of 500 °C and the resulting biochar was modified using NaOH, KOH, NaOH + KOH and HNO3 + HCl. This study investigated the impact of these modifications on the characteristics of the biochar and its effectiveness in adsorbing phenanthrene (Phe) from an aqueous solution. The results indicated that the surface roughness increased, leading to an increase in the specific surface area, and the development of complex pore structure, leading to a decrease in the polarity and increase in hydrophobicity of biochar modified by a mixture of KOH and HNO3 + HCl (EBC-K and EBC-H). The EBC-K and EBC-H samples exhibited superior surface areas (272.76 and 289.60 m2 g-1) and adsorption capabilities for Phe (removal rates of 99.8% and 99.4%). The pseudo-first order, pseudo-second order and intraparticle diffusion Kinetic model demonstrated that the adsorption process is determined by both physicochemical and intra-particle diffusion. The adsorption process was well described by the Langmuir model. The maximum adsorption capacity of EBC-K and EBC-H was increased by approximately 2.4 times compared with the original biochar. Batch adsorption experiments indicated that the removal rate increases with the increase of dosage. Additionally, EBC-H regenerated from n-hexane removed 85.52% of the Phe solution.