Study of the Effect of the Surfactant Linear Alkylbenzene Sulfonate (LAS) on the Coagulation of Aged Microplastic

Objective: Evaluate the effect of linear alkylbenzene sulfonate (LAS) surfactant on the coagulation of aged microplastic. Theoretical Framework: Chemical coagulation is one of the steps adopted in water treatment that can help remove microplastics. During coagulation, suspended particles agglomerate, increasing the efficiency of removing these particles in the sedimentation stage. However, when coagulation occurs in the presence of surfactants, evidence points to deficits in removal capacity. Method: Using Jar Test tests, the optimal parameters for microplastic removal were determined with aluminum sulfate as a coagulating agent in the presence and absence of the surfactant linear alkyl benzene sulfonate (LAS). The LAS concentrations studied were in the range of 20 mg/L to 300 mg/L. Microplastic removal efficiency was evaluated by measuring turbidity. Results and Discussions: The combination of pH and coagulant concentration values that best suited the system were 5.0 and 4.25 mg/L, respectively. Due to the addition of surfactants, a decrease in removal efficiency was observed, with an average value ranging from 94.79% to 76.50% due to the interaction of polyethylene spheres with the surfactant. Research Implications: As explained, due to the coexistence of microplastics and surfactants in the aqueous environment, studies that describe chemical coagulation under these conditions have great value for optimizing treatment systems and technologies. Research Originality/Value: The use of aged microplastics aims to approximate their natural occurrence.