Filter fabrication by constructing metal-organic frameworks membrane on waste maize straw for efficient phosphate removal from wastewater

Abstract

Metal-organic frameworks (MOFs) have been demonstrated as effective adsorbents for removal of phosphate from wastewater, but the difficulty in processing and recycling of powdery MOFs limits their practical application. Shaping MOFs into application-oriented forms meanwhile maintaining their intrinsic property is important but challenging. Here, a novel UiO-66/MS filter is fabricated by constructing UiO-66 membrane on the cell wall of waste maize straw (MS) through a solvothermal process. The unique biological structure of MS provides well-developed channels for mass transfer, and the UiO-66 nanoparticles are uniformly anchored on the cell walls of MS to form a monolayer membrane, promoting the exposure of adsorption sites. Due to these structural advantages, the UiO-66/MS filter exhibits higher efficiency for phosphate removal from water than UiO-66 pellet. To realize continuous phosphate removal, an all-in-one device is fabricated by connecting UiO-66/MS filters in series, over which the residual P content (initial P = 3.0 mg·L−1) in the effluent still meets the primary (<0.5 mg·L−1 at 300 L·m−2·h−1) and secondary (<1.0 mg·L−1 at 800 L·m−2·h−1) standards of China’s integrated wastewater discharge standard. This study not only provides an efficient UiO-66/MS filter for phosphate remediation, but also provides a blueprint for value-added utilization of the waste MS.