Direct reuse at industrial level of ion-exchange resin regeneration wastewater in MDF manufacturing

Industrial wastewater is currently a big challenge for authorities due to its environmental issues when disposed to the ecosystem. From an economic perspective and long treatment time, it is yet more reasonable to recover and reuse wastewater in industries. In this work, the wastewater from an ion exchange resin regeneration process was directly and without any further treatment reused in the wood industry for manufacturing medium density fiberboards (MDF). Comparing with the disposal criteria of international standards, the reused wastewater exhibited much higher electrical conductivity, turbidity, total dissolved solid, total suspension solid, and inorganic salt content than the permissible limits; therefore, it is categorized as hazardous material. The highly saline wastewater was added during and after synthesizing of the urea–formaldehyde (UF) resin but before mixing with the wood fibers. The Fourier transform infrared spectroscopy and differential scanning calorimetry analyses of the UF resin samples, respectively, demonstrated the high stability of the chemical structure and higher strength against decomposition for the UF resins after being treated with the wastewater. The physico–mechanical properties of MDFs prepared by reused wastewater were significantly improved whilst the formaldehyde emission of the boards was noticeably reduced (~ 17%) to the benefit of the environment.