Chitosan/wood sawdust/magnetite composite membranes for the photodegradation of agrochemicals in water

Agrochemicals are potential environmental pollutants due to their toxicity and resistance to degradation. Suitable water, soil and sediment remediation methods are needed to mitigate the environmental impacts of the application of agrochemicals on crops. In this work, chitosan/sawdust/magnetite composite membranes (catalysts) were synthesized, characterized using Fourier-transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and X-ray diffraction (XRD) and used for the photodegradation of agrochemicals [2,4-dichlorophenoxyacetic acid (2,4-D) as pollutant model] in water. FT-IR spectra confirmed the presence of chemical groups in the membrane chains. TGA indicated that the membranes have suitable thermal stability for the photodegradation of 2,4-D in water. SEM images indicated morphological changes after varying the chemical composition of the membrane. X-ray diffractograms indicated the presence of different average crystallite sizes in the membrane chains. The photodegradation efficiency of 2,4-D was affected by the pH and temperature of the aqueous solutions as well as the magnetite content incorporated in the membrane chains. The multilayer formation of magnetite in the membrane structure and the intermolecular interactions between the magnetite and wood fiber affected photodegradation efficiency due to the blocking of UV radiation. The optimal experimental conditions for the photodegradation of 2,4-D in water were i) magnetite content of 5 wt% in the membrane chain, ii) pH 6.0 and iii) temperature of 25 °C. Chitosan/sawdust/magnetite composite membranes proved to be potential catalysts for the photodegradation of agrochemicals in water and wastewater purification processes. Moreover, these membranes can be reused in successive photodegradation cycles.