Preparation of amino functionalized magnetic oyster shell powder adsorbent for selective removal of anionic dyes and Pb (II) from wastewater.

A kind of new magnetic oyster shell (OS) composite (OS-Fe3O4@SiO2@NH2@PEI) was synthesized and used as an adsorbent to remove carmine (CM), sunset yellow (SY) and Pb (II) from water. Firstly, Fe3O4 magnetic nanoparticles were introduced on the surface of waste oyster shell powder, then amino silanization was used to improve the stability of the material, and finally polyethylenimide (PEI) was grafted by Schiff base reaction. The composite was characterized by FT-IR, SEM, EDS, XPS, VSM, BET, TEM and zeta potential. The effects of adsorbent dosage and initial solution pH on the three samples were investigated by adsorption experiments. The adsorption kinetics and isotherms were investigated in depth under the best experimental conditions. The composite adsorbent not only selectively removed anionic azo dyes, but also had good recycling. In addition, OS-Fe3O4@SiO2@NH2@PEI still had good performance in mixed samples. These results indicated that OS-Fe3O4@SiO2@NH2@PEI was successfully used for the removal of a wide range of anionic dyes and heavy metal ions from the environment, and provided a new strategy for recycling waste.

Facile synthesis of high-efficiency magnetic graphitic carbon nitride adsorbents for the selective removal of hazardous anionic dyes in wastewater.

In this study, a kind of novel magnetic composite, PEI-Fe3O4/g-C3N4, was synthesized by simple physical impregnation and used as an adsorbent to remove the anionic dye Congo red (CR) in water. The structural properties of composites were studied using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM), Brunauer-Emmett-Teller (BET) measurements and zeta potential techniques. PEI-Fe3O4/g-C3N4 could selectively remove anionic dyes from aqueous solutions. The adsorption kinetics and isotherms were systematically studied, and the adsorption process is in accordance with the pseudo-second-order kinetic model and Langmuir isotherm model. The thermodynamic results indicated that adsorption is a process of spontaneous heat entropy increase. CR-sorbed PEI-Fe3O4/g-C3N4 was successfully desorbed with a NaOH solution, and 0.05 M NaOH had the best desorption effect. Furthermore, PEI-Fe3O4/g-C3N4 exhibited excellent recyclability and reusability. The results of the adsorption mechanism study indicated that the excellent adsorption performance of PEI-Fe3O4/g-C3N4 was attributed to the favorable electrostatic interaction, hydrogen bonding and π-π interactions between the adsorbent and CR. In addition to its excellent adsorption properties, the prepared adsorbent showed satisfied adsorption performance in actual water samples. Predictably, the prepared adsorbent has a potential application value in the environmental field.