Synthesis, characterization, and application of pristine and clay-templated carbon xerogel microspheres for removing diclofenac and heavy metals from water solution

Organic xerogel microspheres (SX) were synthesized by inverse emulsion sol-gel polymerization and carbonized to obtain carbon xerogel spheres (SXCs). The catalyst was K2CO3 or Fe(C2H3O2)(2), and the clay sodium sepiolite (SNa) or exfoliated vermiculite (V(ex)f) was added during the synthesis. Depending on the catalyst and clays, the SXCs were designated SXC-K, SXC-Fe, V-exf-K, V-exf-Fe, SNa-Fe, and SNa-K. At pH = 7 and T = 25 degrees C, the SXCs' adsorption capacities towards diclofenac (DCF) in water increased as follows: SXC-K < SXC-Fe < SNa-Fe < SNa-K SX-Fe > SXC-K > SXC-Fe, indicating that the non-carbonized materials (SX) presented higher adsorption capacity than the SXCs because the SXs had a higher acidic site content. Adding SNa or V-exf to SXs enhanced the adsorption capacity towards Cd(II), and SNa-SX-K presented an exceptionally high capacity of 182.7 mg/g. This synergistic effect revealed that the -Cd2+ was adsorbed on the SX-K acidic sites and by cation exchange on the SNa.

Automated summary

Organic xerogel microspheres (SX) were synthesized and carbonized to obtain carbon xerogel spheres (SXCs). The addition of clay sodium sepiolite (SNa) or exfoliated vermiculite (V(ex)f) enhanced the adsorption capacity towards Cd(II). The synergistic effect revealed that Cd2+ was adsorbed on the SX-K acidic sites and by cation exchange on the SNa.