Superior selective adsorption of MgO with abundant oxygen vacancies to removal and recycle reactive dyes

Abstract

• MgO realized the selective removal and recovery of reactive dyes. • Oxygen vacancies are the selective adsorption sites to reactive dyes. • MgO displayed high cycle stability. • The selective removal capacity was ~800 L h −1 kg −1 (MgO) . In textile engineering, wasted mixture dyes are often discharged and need to be separated and recycled. To solve this problem, MgO with abundant oxygen vacancies (F + centers, F + -MgO) is studied as a selective adsorbent for the recycling and separation of organic dyes. Herein, the adsorption performance of F + -MgO to reactive dyes Reactive blue 19, Reactive red 195, Congo red (RB19, RR195, CR), and non-reactive dyes Methylene blue and Rhodamine B (MB and RB), and the dyes mixture are estimated. Our results present that F + -MgO exhibits the properties of selective adsorption, separation, and recovery of reactive dyes from the dyes mixture. Equilibrium adsorption capacities ( q eth ) of F + -MgO are 549.45 mg/g to RB19, 348.43 mg/g to CR, and 442.48 mg/g to RR195, while hardly adsorption for MB and RhB, respectively. Moreover, RB19 can be quickly separated by F + -MgO from the mixture of RB19 and RhB in 90 s with an initial concentration of 50 mg/L. Furthermore, XPS, PL, and EPR confirm that the surface oxygen vacancies exist on the F + -MgO. And the surface oxygen vacancies are affirmed as adsorption active sites by reduced adsorption capacity after H 2 O 2 treatment and heated at high temperature in O 2 . The recycling of the used adsorbent F + -MgO is achieved by calcinated F + -MgO at high temperature, and the adsorption efficiency remains high (96.02%) after seven cycles. Notably, the adsorbed dyes (RB19) also can be reused by dissolution MgO into the solution. In this work, a low-cost, high-efficient, and recyclable adsorbent is applied to recover used-dyes from textile wastewater, presenting a new closed-loop sustainable strategy.