Acid mine drainage treatment by fertilizer drawn forward osmosis for irrigation

Abstract

This work utilized fertilizer driven forward osmosis (FDFO) to extract fresh water from acid mine drainage (AMD) wastewater for irrigation, and investigated the effects of draw solutes on membrane fouling behaviours. The carbon nanotubes (CNTs) and polydopamine (PDA) were coated on the thin film nanofibrous composite (TFNC) membrane #FO-0 as anti-fouling modification. When 1 M NH4H2PO4 (MAP) and 500 mg/L copper AMD wastewater (pH=3.0) used as draw and feed solutions, #FO-0 and PDA-coated TFNC membrane (#FO-PDA) exhibited rapid declines of water fluxes due to the dense fouling layer. In contrast, the CNT-coated membrane #FO-CNT exhibited the lowest flux decline of 26.0% attributed to better hydrophilicity, the lowest roughness and neutral surface charge. All the TFNC membranes exhibited insignificant membrane fouling when (NH4)2SO4 (SOA) was used as draw solute. Additionally, the osmotic backwashing could effectively recover water flux. The discharged draw solution promoted plant growth without posed potential health threat.