Ionic resource recovery for carbon neutral papermaking wastewater reclamation by a chemical self-sufficiency zero liquid discharge system

Papermaking industry discharges large quantities of wastewater and waste gas, whose treatment is limited by extra chemicals requirements, insufficient resource recovery and high energy consumption. Herein, a chemical self-sufficiency zero liquid discharge (ZLD) system, which integrates nanofiltration, bipolar membrane electrodialysis and membrane contactor (NF-BMED-MC), is designed for the resource recovery from wastewater and waste gas. The key features of this system include: 1) recovery of NaCl from pretreated papermaking wastewater by NF, 2) HCl/NaOH generation and fresh water recovery by BMED, and 3) CO2 capture and NaOH/Na2CO3 generation by MC. This integrated system shows great synergy. By precipitating hardness ions in papermaking wastewater and NF concentrate with NaOH/Na2CO3, the inorganic scaling on NF membrane is mitigated. Moreover, the NF-BMED-MC system with high stability can simultaneously achieve efficient CO2 removal and sustainable recovery of fresh water and high-purity resources (NaCl, Na2SO4, NaOH and HCl) from wastewater and waste gas without introducing any extra chemicals. The environmental evaluation indicates the carbonneutral papermaking wastewater reclamation can be achieved through the application of NF-BMED-MC system. This study establishes the promising of NF-BMED-MC as a sustainable alternative to current membrane methods for ZLD of papermaking industry discharges treatment.

Automated summary

The papermaking industry generates large amounts of wastewater and waste gas, and their treatment often involves the use of chemicals, lacks resource recovery, and consumes high amounts of energy. In this study, a chemical self-sufficiency zero liquid discharge (ZLD) system called NF-BMED-MC was designed to recover resources from papermaking wastewater and waste gas. This integrated system has shown great synergy by utilizing nanofiltration, bipolar membrane electrodialysis, and membrane contactor technologies. It enables the recovery of NaCl, generation of HCl/NaOH, and CO2 capture, while achieving efficient water recovery and resource purification without the need for additional chemicals. The study also demonstrates the potential of NF-BMED-MC as a sustainable alternative for the ZLD treatment of papermaking industry discharges.