Exploring novel magnetic nanocomposite coagulants utilization for advanced drilling wastewater treatment and optimization

Efficient and sustainable wastewater management is crucial for preserving freshwater resources. This study explores the novel application of a magnetic nanocomposite (MNC) for treating drilling wastewater, aiming to integrate magnetic properties into chemical contaminant adsorbents to create a regenerative coagulant. Polyaluminum chloride (PAC), a widely used synthetic coagulant with surface load-neutralizing capabilities, is often paired with polyacrylamide (PAM), a common flocculant and cross-linking agent, in hybrid coagulation-flocculation processes. Using a pre-mixing compositing approach, magnetic nanoparticles (MNPs) are incorporated into the structure. Their effects on Total Dissolved Solids (TDS) removal, Total Suspended Solids (TSS) removal, and Turbidity Reduction Rate (TRR) were analyzed via parametric study and response surface design of experiments, employing Central Composite Design. Numerical models were developed for each response, with variance analysis revealing complex interdependent effects. MNP concentration notably influenced all responses, enhancing performance through its magnetic properties. Unique mechanisms supported each response based on the combined effects of PAM and PAC. For example, TDS removal was achieved through a four-step PAC-MNP interaction, while rapid floc sedimentation was observed from MNP-PAM cluster formation. Given wastewater management's multifaceted requirements-recycling, reusing, and releasing-four optimization scenarios were evaluated for practical applications. The highest experimental values were 63.12% for TDS removal, 78.78% for TSS removal, and 10.61 NTU/min for TRR. Optimal results of 61.97% TDS removal, 79.00% TSS removal, and 5.03 NTU/min TRR were achieved using 0.50 g/L PAC, 0.40 g/L PAM, and 0.17 g/L MNP in the general optimization scenario without TRR boundary constraints.