Geopolymers (GPs) are aluminosilicate-based materials, characterized by -Si-O-Al-O- chains. Because of their green properties (i.e. low temperatures synthesis, industrial and agricultural waste feedstocks, etc.) and excellent physicochemical properties (i.e. high mechanical strength, resistance to low and high temperatures, etc.), GPs can be considered as adsorbents for environmental friendly applications, such as the removal of pollutants from waters. Moving from the above-mentioned assumptions, in this work, adsorption properties of several GPs, characterized by different shapes and structures, towards glyphosate (a well-known herbicide with toxic effects against environment and human beings) in water matrices are presented. To highlight the possible interaction mechanisms, the contribution of selected synthesis parameters was investigated, in particular: i) GPs shape, testing both powdered and 3-dimensional printed supports; ii) functionalization with specific agents, that were supposed to enhance the interaction towards glyphosate (i.e. magnetite, zeolites and commercial activated carbons with anion-exchange properties, etc.); iii) interaction with templating agents employed for the synthesis or the printing (e.g. bentonite and PEG1000). Aliquots of 0.2 g of each material were put in contact with 50 mL of 2 mg/L glyphosate solution, analysing the residual concentrations by means of ion exchange chromatography coupled with suppressed conductivity detection. Results showed that 3D-printed GPs have good adsorption performances towards glyphosate (removal rates up to 45% for sorbents modified with both active carbons and zeolite), as well as for GPs doped with magnetite nanoparticles (58%). The higher interaction obtained using magnetite doped GPs was ascribed to the selective complexation of Fe atoms with the phosphate group of the herbicide. On the contrary, a negative effect of printing agents in particular for sodium bentonite was demonstrated since they reduce the adsorption capacities of 3D GPs of about 15%, tentatively ascribed to an obstruction in the sorbent reticulate. This study confirms the affinity of 3D printed shape GP sorbents towards glyphosate; their potential use for water treatments is encouraged by their limited backpressure in respect to powder systems.
Affinity of geopolymer based ion-exchange media for glyphosate in water matrices
M. Castiglioni;L. Rivoira;I. Ingrando;M. C. Bruzzoniti
2021-01-01
Abstract
Geopolymers (GPs) are aluminosilicate-based materials, characterized by -Si-O-Al-O- chains. Because of their green properties (i.e. low temperatures synthesis, industrial and agricultural waste feedstocks, etc.) and excellent physicochemical properties (i.e. high mechanical strength, resistance to low and high temperatures, etc.), GPs can be considered as adsorbents for environmental friendly applications, such as the removal of pollutants from waters. Moving from the above-mentioned assumptions, in this work, adsorption properties of several GPs, characterized by different shapes and structures, towards glyphosate (a well-known herbicide with toxic effects against environment and human beings) in water matrices are presented. To highlight the possible interaction mechanisms, the contribution of selected synthesis parameters was investigated, in particular: i) GPs shape, testing both powdered and 3-dimensional printed supports; ii) functionalization with specific agents, that were supposed to enhance the interaction towards glyphosate (i.e. magnetite, zeolites and commercial activated carbons with anion-exchange properties, etc.); iii) interaction with templating agents employed for the synthesis or the printing (e.g. bentonite and PEG1000). Aliquots of 0.2 g of each material were put in contact with 50 mL of 2 mg/L glyphosate solution, analysing the residual concentrations by means of ion exchange chromatography coupled with suppressed conductivity detection. Results showed that 3D-printed GPs have good adsorption performances towards glyphosate (removal rates up to 45% for sorbents modified with both active carbons and zeolite), as well as for GPs doped with magnetite nanoparticles (58%). The higher interaction obtained using magnetite doped GPs was ascribed to the selective complexation of Fe atoms with the phosphate group of the herbicide. On the contrary, a negative effect of printing agents in particular for sodium bentonite was demonstrated since they reduce the adsorption capacities of 3D GPs of about 15%, tentatively ascribed to an obstruction in the sorbent reticulate. This study confirms the affinity of 3D printed shape GP sorbents towards glyphosate; their potential use for water treatments is encouraged by their limited backpressure in respect to powder systems.
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