To treat wastewater with wastes: a highly efficient flocculant from fly ash and rice straw†

Water resources are vital for sustainable human life and economic activities. However, the issue of water pollution has reached alarming levels. Coking wastewater, known for its high concentrations of organic matter and toxic substances, poses significant environmental hazards. In response to this challenge, we developed a novel composite flocculant called polymeric aluminum ferric chloride (PAFC)/rice straw (PAFC/RS) from fly ash (a coal waste) and rice straw (an agricultural waste). The PAFC/RS was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and Fourier transformed infrared (FT-IR). The flocculation performance of PAFC/RS was studied utilizing humic acid simulated coking wastewater as the target by measuring the chemical oxygen demand (COD), UV₂₅₄, and turbidity. A removal efficiency of 97.3% for turbidity, 79.7% for COD, and 98.2% for UV₂₅₄ was reached for the PAFC/RS with an optimal composition. It demonstrated a better flocculation effect compared to the traditional aluminum–iron-based inorganic flocculant. The PAFC/RS possesses great potential for a straightforward, cost-effective, and environmentally friendly water treatment material.