Zero liquid discharge hybrid membrane process for separation and recovery of ions with equivalent and similar molecular weights

Separation of similar ions through nanofiltration (NF) is advantageous for many different applications such as, resource recovery and the reduction of waste discharge. The production of pigments generates a solution comprising of acetate (Ac⁻) chloride (Cl⁻) ions, in which the Ac⁻ can be profit as recovered chemical. To recover these ions in this work we propose the use of a hybrid zero liquid discharge (ZLD) system. The ions rejections in this work reached 81.8% and −7.6%, for Ac⁻ and Cl⁻ ions respectively. This selectivity was achieved using NF with a separation ratio of 5.9. The recovery of these chemicals is highly advantageous as it can not only significantly reduce the waste discharge for the pigment industry, but also offset the cost of water treatment. When using mechanical vapor recompression (MVR), a cost is incurred (−0.04 $·t⁻¹) and without the use of MVR a profit is made (2.73 $·t⁻¹). The proposed strategy in this work may shed light on the heavily polluting industry towards environmentally friendly and economical wastewater treatments.