Dispersive Solid–Liquid Microextraction Based on the Poly(HDDA)/Graphene Sorbent Followed by ICP-MS for the Determination of Rare Earth Elements in Coal Fly Ash Leachate

A dispersive solid-phase microextraction (DSPME) sorbent consisting of poly(1,6-hexanediol diacrylate)-based polymer microspheres, with embedded graphene microparticles (poly(HDDA)/graphene), was synthesized by microfluidic emulsification/photopolymerization and characterized optical microscopy X-ray fluorescence spectrometry. This applied for simple, fast, sensitive vortex-assisted DSPME rare earth elements (RREs) in coal fly ash (CFA) leachate, prior to their quantification inductively coupled plasma mass spectrometry (ICP-MS). Among nine variables, the Plackett–Burman screening design (PBD), followed central composite optimization (CCD) using Derringer desirability function (D), identified eluent type as most influencing variable. The optimum conditions maximum D (0.65) chelating agent di-(2-ethylhexyl) phosphoric acid (D2EHPA) amount, eluting solvent, extraction temperature, centrifuge speed, vortexing time, elution centrifugation pH, were set 60 ?L, 30 mg, 2 M HNO3, 25 °C, 6000 rpm, 1 min, 5 4.2, respectively. Analytical validation method 16 REEs (Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) CFA leachate samples estimated detection limits at low ppt level, recovery range 43–112%, relative standard deviation within ± 22%. a water procedure (EP) acetic toxicity characteristic leaching (TCLP) CFA, from five different coal-fired thermoelectric power plants. abundant (20 ÷ solid-to-liquid ratio) are which found 22–194 ng/L, 35–105 48–95 9.6–51 ?g/L, 7.3–22 2.4–17 EP TCLP least present REE Lu (42–125 ng/L), not detected leachate.