Preparation, characterization and applications of graphene oxide and oil-palm activated carbon modified magnetic-polypyrrole sorbents for microextraction of selected organic pollutants

Abstract

Magnetite (Fe3O4) and polypyrrole (PPy) are widely used in the electrical industry. However, their uses as sorbents in analytical chemistry applications are scarce. Thus, this research investigates the preparation, development and applications of Fe3O4-PPy composites as sorbents for microextraction of different emerging and persistent occurring pollutants optimized with the aid of response surface methodology (RSM) approach. In the first part of study, Fe3O4-PPy sorbent was applied in magnetic solid phase extraction (MSPE) combined with high-performance liquid chromatography-ultraviolet detection (HPLC-UV) for the analysis of three selected non-steroidal anti-inflammatory drugs (NSAIDs), namely naproxen, diclofenac and mefenamic acid. Systematic investigations on the synthesis and Fe3O4-PPy MSPE efficiencies for the NSAIDs were successfully modelled using the Box- Behnken Design (BBD) (R2 = 0.94-0.98, p < 0.001%). A comparison of the use of RSM and one-variable-at-a-time approach showed more positive implications of the former in terms of order of factor significance and result prediction. Optimized conditions for the procedure gave low limits of detection (LOD = 3s, 0.9-3.5 ^g L-1) and limits of quantitation (LOQ = 10s, 2.9-11.5 ^g L-1) with good reproducibility (relative standard deviation, RSD < 7.2%) and excellent recoveries (97.9 - 100.5%) for tap water, river water, and wastewater samples. In order to enhance the surface ability of the sorbent, Fe3O4 -PPy was incorporated with graphene oxide, (GO) to produce GO-Fe3O4-PPy in the second part of study. The synthesized GO-Fe3O4-PPy composite was applied in MSPE of three selected neonicotinoids namely imidacloprid, thiacloprid and thiamethoxam, in water samples using HPLC-UV detection. Experimental results obtained with aid of RSM-BBD were in good agreement (97%) with the model predictions. The surface morphology of GO-Fe3O4-PPy showed that the synthesized Fe3O4 was embedded within the slits of GO and that PPy sealed the GOFe3O4 surface to produce an effective sorbent for the extraction of neonicotinoids in water matrices. Analysis showed excellent LOD and LOQ (LOD = 3s, 0.026- 0.045 ^g L-1; LOQ = 10s, 0.087- 0.149 ^g L-1) with good recoveries of 93-102%. In the quest for a rapid analytical extraction method, the third part of study was performed where oil-palm activated carbon (OPAC) was incorporated with Fe3O4 -PPy to produce OPAC-Fe3O4 -PPy for MSPE of two selected organochlorine pesticides (OCPs) namely endosulfan (ESO) and dieldrin (DIE) in aquatic samples. Analysis was performed using gas chromatography with microelectron capture detection. The effects of three preparation variables, namely ratio of Fe3O4:OPAC, amount of pyrrole monomer, and amount of FeCl3 oxidant were optimized successfully using RSM-BBD (R2 < 0.99, p < 0.001%). RSM-BBD was also used for the optimization of four numerical parameters in MSPE. The significance of MSPE parameters were salt addition > pH sample solution > extraction time > desorption time. The OPACFe3O4- PPy MSPE method demonstrated good linearity (25-1000 ng L-1) with good correlation (R2 > 0.991) and low LODs and LOQs (LOD = 3S/N, 6.5 ng L-1 for ESO and 7.3 ng L-1 for DIE; LOQ = 10S/N, 25 ng L-1 for ESO and DIE) with high recoveries (98105%) of OCPs from tap water, and palm oil effluent samples. A comparative study showed that the incorporation of Fe3O4 and PPy separately to GO and OPAC, showed different behaviours in accordance to the particle size and surface chemistry. The adsorption capacities of the sorbents, represented by qm is in the order of GO-Fe3O4 -PPy > OPAC-Fe3O4 -PPy > Fe3O4-PPy. Thus this study proved that the adsorption strength of sorbents could be reinforced by the presence of OPAC and GO. Analytical Eco-Scale analysis showed that all the developed methods achieved acceptable green analysis scale (AES value: 77-81). The proposed methods offered good features such as sustainable, simple, and rapid extraction that meet the green chemistry concept.