Recent advancement in the application of hybrid coagulants in coagulation-flocculation of wastewater: A review

Hybrid coagulants have recently received attention in water and wastewater treatment technologies mainly due to their cost-efficiency and exceptional performance. As such, this study highlights the recent advanced applications of hybrid coagulants in wastewater treatment. The materials used for hybrid coagulants, such as those hybridised in chemical bond, structurally-hybridised, and functionally-hybridised under certain combination techniques (e.g., organic/inorganic, organic/organic, inorganic/inorganic, organic/natural polymer, inorganic/natural polymer, organic/biopolymer, & inorganic/biopolymer), were evaluated and compared based on their applications on different type of wastewaters, experimental conditions, and treatment efficiency. The performance of inorganic/inorganic hybrid coagulation demonstrated high removal of turbidity (98.5%), chemical oxygen demand (COD) (73.3%), heavy metals (99.2%), and colour (98%) - seemingly better than organic removal efficiency. The optimum operational conditions for inorganic/organic coagulants at varied pH levels (6–12) lowered the cost for chemicals used for pH adjustment in treating industrial wastewater. Referring to the review outcomes, hybrid coagulation applications are indeed efficient for treatment of highly concentrated industrial wastewater, such as oily wastewater.