SiO2 nanospheres as surfactant and template in aqueous dispersion polymerizations yielding highly nanoporous resin particles

• Published in: Journal of colloid and interface science Vol. 637; pp. 372 - 388
• Main Authors: Borchert, Konstantin B.L., Gerlach, Niklas, Steinbach, Christine, Reis, Berthold, Schwarz, Simona, Schwarz, Dana
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.05.2023
• Subjects: Colloidal synthesis; Dichromate; Fixed bed adsorption; Hard templating; Poly(melamine-co-formaldehyde); Porous particles; Water treatment; Water treatment; SiO2 NPs; K1; K2; Dichromate; EAds; K; ceq; cS; P-PMF; R; ma; T; EFTEM; E(t); qeq; Colloidal synthesis; ICP-OES; Porous particles; Hard templating; PSD; a; KL; b; N0; Fixed bed adsorption; H-PMF; PMF; h; KS; Poly(melamine-co-formaldehyde); QSDFT; c0; n; BET; SEM-EDX; β; u; ε; t0.5; v; VL; SEM; Qm; TEM
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2023.01.071

[Display omitted] •Poly(melamine-co-formaldehyde) (PMF) was templated with SiO2 nanospheres in H2O.•SiO2 acted as both Pickering-surfactant and template in the synthesis.•PMF prepolymer concentration is decisive for inclusion of SiO2 into the resin.•This is the first reported aqueous synthesis of porous, column-suitable particles.•The column material was an efficient adsorbent exemplarily shown for dichromate. High nitrogen containing resins such as poly(melamine-co-formaldehyde) (PMF) are known for their very good adsorption properties. Until now, using an ecofriendly hard-templating approach with SiO2 nanospheres in water for synthesis, only yielded either highly porous particles with diameters up to 1 µm or non-porous particles with diameters above 1 µm. Small particles cannot be used as fixed bed adsorbents in columns because of the very high pressure occurring. To yield particles with high porosity and larger diameters for the use as fixed bed adsorbent, we investigated the influence of several synthesis parameters on porosity and particle morphology. From all variations, we proposed a mechanism for the complex interplay between the PMF prepolymer and resin species with SiO2 nanoparticles acting both as Pickering-like surfactant and template particle. With this knowledge we were able to produce a suitable column material with high specific surface area up to 260 m2/g. We then proved the application of this material for aqueous dichromate adsorption in batch, yielding a maximum capacity of 138 mg/g with recyclability. In column experiments, the contamination of 5 mg/L dichromate in water was reduced to drinking water safe levels for an influent volume equal to over 160 bed volumes.