Adsorption of Cu(II) by phosphogypsum modified with sodium dodecyl benzene sulfonate.

Phosphogypsum (PG) is a solid waste generated during the wet production of phosphoric acid, and stockpiling PG causes serious pollution to the environment. Therefore, we prepared an adsorption material modified with sodium dodecyl benzene sulfonate (SDBS) based on PG (SDBS@PG). SDBS@PG can be regenerated and used in several adsorption-desorption cycles. The optimum conditions for Cu(II) removal are as follows: the Cu(II) concentration is 10 mg/L, the amount of adsorbent is 1.6 g/L, the pH is 6, and the contact time is 60 min. Under these conditions, the removal rate is 99.23 %. The kinetic data of adsorption conform to the pseudo-second-order model. The equilibrium isotherm results are consistent with the Langmuir isotherm equation. Furthermore, plausible mechanisms were proposed: PG was modified with SDBS, which greatly improved the adsorption of Cu(II) onto PG. The main reason is that SDBS is adsorbed on the surface of PG by chemical action in the form of micelles and then Cu(II) is adsorbed on the anionic SDBS micelles of SDBS@PG due to chemical and electrostatic interactions. This work indicates that SDBS@PG can be used for the removal of Cu(II) and is qualified for practical application.