Preparation of a rice straw-based green separation layer for efficient and persistent oil-in-water emulsion separation

Inefficiency, high cost, and complex operation have emerged as shackles for large-scale separate oil-in-water emulsion. Herein, a low-cost and eco-friendly separation layer with a rough structure and rich anionic groups was fabricated from rice straw (RS) via a simple acid-base treatment and slight squeeze process. The separation layer's morphology, composition, and wettability were investigated. It was then employed to separate oil-inwater emulsion. The RS after acid and alkali treatment (A1A2-RS) exhibited a clear fiber structure and abundant humps, which made the separation layer superwettable and highly electronegative (-26.55 mV). The overlapped and intertwined A1A2-RS layer structure owned a superior performance for hexadecyl-trimethylammonium-bromide (CTAB) adsorption and tiny oil interception. As a result, the separation layer had stable fluxes ( 500 LMH) for multiple CTAB-stabilized emulsions and the obtained filtrates performed low total organic carbon (TOC) contents (<30 mg/L). In addition, the A1A2-RS layer had excellent renewability (10 cycles/ 200 mL) and the flux could be substantially recovered merely by aqueous wash. Moreover, filtrate analysis showed that the A1A2-RS layer had a good effect on actual emulsion treatment with a TOC removal rate of 89.56%.

Automated summary

An efficient and eco-friendly separation layer was fabricated from rice straw for large-scale oil-in-water emulsion separation, exhibiting superwettability and high electronegativity. The overlapped and intertwined structure of the layer showed excellent performance for CTAB adsorption and oil interception, leading to stable fluxes and low TOC contents in the obtained filtrates. The renewability of the separation layer was demonstrated through multiple cycles with substantial flux recovery, and effective emulsion treatment with a high TOC removal rate was achieved.