Amphiphilic magnetic copolymer for enhanced removal of anionic dyes: Fabrication, application and adsorption mechanism

Fabrication of polyethyleneimine functionalized magnetite nanoparticles for recyclable recovery of fucoidan from aqueous solution

Fucoidan is a kind of natural water-soluble fucose-rich sulfated polysaccharide with promising applications in the food and pharmaceutical industry. However, the traditional methods for fucoidan recovery from aqueous solution are expensive, time-consuming, and environmentally unfriendly. In this work, polyethyleneimine functionalized magnetite nanoparticles (PEI-MNPs) with well-defined core-shell structures were prepared by a Layer-by-Layer (LbL) approach using sodium tripolyphosphate (STPP) as a cross-linker. The as-prepared PEI-MNPs showed improved adsorption capability towards fucoidan at pH 4-8 due to the high density of cationic groups on the surfaces and the absence of internal pores. It was found that the adsorption process of fucoidan onto PEI-MNPs can reach to equilibrium in 50 min at room temperature. The maximum qe derived from the Langmuir isotherm at room temperature was 169.1 mg per g at a pH of 7. A selective fucoidan capture over a model protein BSA can be realized by adjusting pH (6-8) and salt concentration (0.5-2.5 M). The PEI-MNPs loading with fucoidan can be isolated from the final products by a neodymium magnet and regenerated by 4 M NaCl solution as stripping reagent. Therefore, this novel kind of PEI-MNP could be a promising candidate for highly efficient and recyclable recovery of fucoidan from an aqueous solution.

Magnetic Adsorbents for Wastewater Treatment: Advancements in Their Synthesis Methods

The remediation of water streams, polluted by various substances, is important for realizing a sustainable future. Magnetic adsorbents are promising materials for wastewater treatment. Although numerous techniques have been developed for the preparation of magnetic adsorbents, with effective adsorption performance, reviews that focus on the synthesis methods of magnetic adsorbents for wastewater treatment and their material structures have not been reported. In this review, advancements in the synthesis methods of magnetic adsorbents for the removal of substances from water streams has been comprehensively summarized and discussed. Generally, the synthesis methods are categorized into five groups, as follows: direct use of magnetic particles as adsorbents, attachment of pre-prepared adsorbents and pre-prepared magnetic particles, synthesis of magnetic particles on pre-prepared adsorbents, synthesis of adsorbents on preprepared magnetic particles, and co-synthesis of adsorbents and magnetic particles. The main improvements in the advanced methods involved making the conventional synthesis a less energy intensive, more efficient, and simpler process, while maintaining or increasing the adsorption performance. The key challenges, such as the enhancement of the adsorption performance of materials and the design of sophisticated material structures, are discussed as well.

Biosorption study of amaranth dye removal using Terminalia chebula shell, Peltophorum pterocarpum leaf and Psidium guajava bark

Amaranth dye (AD) is trisodium (4E)-3-oxo-4-[(4-sulfonato-1- naphthyl) hydrazono] naphthalene-2, 7-disulfonate and anionic in nature. In the present investigation, waste biomasses such as Terminalia chebula shell (TCS), Peltophorum pterocarpum leaf (PPL) and Psidium guajava bark (PGB) are explored as biosorbents for the first time toward the removal of AD from aqueous solution in a batch method. Influence of biosorption parameters such as pH, initial concentration of AD, biosorbents (TCS, PPL, PGB) dosage, temperature and contact time was studied. Biosorption equilibrium data was analyzed using two parameter isotherms. The kinetics of the biosorption process was analyzed using different models to understand the rate-determining step. The results of the biosorption experiment and modeling investigation illustrated that the pseudo-second-order rate equation fits the experimental data and further the experimental results showed Langmuir isotherm fitted well the biosorption equilibrium data. TCS showed more efficiency toward the removal of AD than PPL and PGB. The value of enthalpy for TCS is 1.527 kJ/mol suggests that the AD removal process is endothermic. The positive value of entropy is 6.429 J/mol K indicates that the particle is randomly disordered and negative values of standard Gibbs free energy (ΔG°) suggested that the biosorption process is spontaneous.Novelty statementBiomasses of Terminalia chebula shell (TCS), Peltophorum pterocarpum leaf (PPL) and Psidium guajava bark (PGB) reported as first time explored biosorbent for amaranth dye (AD) removal from aqueous solution.Optimal biosorption parameter for AD removal determined.Experimental data examined using isotherm, kinetic and thermodynamic analysis.