Magnetic agar-cellulose hydrogel/g-C₃N₄/ZnAl LDH@Fe₃O₄ nanocomposite for efficient pirimicarb removal and antibacterial water purification.

This study focused on the development and application of a highly effective magnetic porous nanocomposite for the adsorption of pirimicarb, a carbamate pesticide commonly used for aphid control. This nanocomposite was prepared using agar, cellulose, graphitic carbon nitride, and ZnAl layered double hydroxide (Agar-Cellulose hydrogel/g-C3N4/Zn-Al LDH@Fe3O4), and was characterized using various techniques, including FT-IR, XRD, SEM, VSM, and TGA. Optimization using response surface methodology (RSM) identified the best conditions as pH 7.2, contact time 94.4 min, adsorbent dosage 2.9 gL-1, and initial pirimicarb concentration 62.6 mg L-1, achieving a maximum removal efficiency of 99.55 % (with an R2 of 0.99). The adsorption process exhibited a high adsorption efficiency and equilibrium capacity (R% = 0.98.62, and qe,exp = 21.49 mgg-1), and model fitting revealed strong agreement with the Freundlich isotherm (kf = 4.54 (mgg-1).(l/mg)1/n, n = 1.62, R2 = 0.99) and the Elovich kinetic model (α = 9.01 mg/g.min, β =0.542 g mg-1, R2 = 0.98). Additionally, the nanocomposite maintained over 81 % removal efficiency after eight adsorption-desorption cycles and demonstrated significant antibacterial activity against Escherichia coli and Staphylococcus aureus bacterial strains. Importantly, when applied to a real water sample containing various co-existing pollutants, the adsorbent achieved an adsorption efficiency of 87.76 % under optimal conditions. This slightly reduced efficiency is likely due to competitive adsorption and matrix effects from other contaminants present in the real sample. These results demonstrate the composite's high adsorption capacity, reusability, and antibacterial properties, making it a promising candidate for sustainable water purification and environmental remediation.