An application of the Taguchi method to optimise SPION synthesis for remediation applications

Industrial activity and accidental spillage has left many sites throughout Europe with unacceptable levels of contaminants in soil, surface water and groundwater, and a range of legislation has been put in place requiring that the contamination is reduced to acceptable levels (Cundy et al. 2008). Remediation methods based on magnetic iron oxides are being developed where the contaminant (organics, metals and inorganic material) is adsorbed on the functionalised iron oxide, and removed by application of a magnetic field (Palanisamy et al., 2013, Kumar et al. 2015). The nanoparticles are reported to be biocompatible, with low toxicity, based on studies in mammals or in-vitro using human cells (Mahmoudi et al. 2011, Barrow et al. 2015), but the environmental effect of these nanoparticles has not been established. Neyaz et al., (2013) reported that superparamagnetic iron oxide nanomaterials (SPIONs) can be separated and re-generated making them cost-effective for remediation, and highlighted the challenge of tightly controlling the physical properties for optimising remediation.
The Taguchi method, a procedure employed in process optimisation by industry, uses a matrix of experiments, designed statistically to test the effect of multiple factors at the same time. It generates robust data in a few experiments, and is an efficient way to identify factors controlling properties and so optimise the product. This method has been applied to nanoparticles for a limited number of syntheses, including silver (Kim et al., 2009), zinc oxide (Kim et al., 2007) and silica (Chiang et al., 2011), but the technique has not been applied to SPION preparation. In this work we will optimise SPION preparation using the Taguchi method to improve the removal of organics, heavy metal models for radionuclides and arsenic, from water, by studying the influence of nanoparticle size, size distribution, magnetism and coatings on remediation of these contaminants. The environmental stability of the SPIONs will be established, and toxicity of the optimised nanoparticles will be determined for Pseudomonas putida, a bacterium in soil, and Daphnia magna, the water-flea.