Hydroxyl modified nano calcium phosphate, a novel adsorbent for denitrogenation of fuel: Synthesis, characterization and adsorptive performance for quinoline

Adsorptive removal of nitrogen-containing compounds from fuels still faced the challenge of efficient and low-cost adsorbents exploitation. In this study, a novel material hydroxyl modified nano calcium phosphate was hydrothermally synthesized using Polyethylene glycol-4000 (PEG-4000) as template, and used as an efficient and low-cost adsorbent for quinoline removal from model fuel. The hydroxyl modified nano calcium phosphate obtained an excellent morphology of fine nanoparticles by regulating the Ca/P mol ratio and the PEG-4000 amount during synthesis, and thus obtained the intergranular pores. Meanwhile, a number of hydroxyl groups were introduced into the nano calcium phosphate to obtain more solid acidity. The adsorption efficiency of quinoline over the hydroxyl modified nano calcium phosphate was significantly enhanced, being attributed to the improvements in morphology, structure and solid acidity properties. 0.1 g of an optimal adsorbent achieved 94 % removal of quinoline with 70 ppm of initial N concentration in 20 mL model fuel within 10 min. Mechanism study proposed that the adsorption process occurred on both the outer surface and the inner pores of hydroxyl calcium phosphate, and thus the rich hydroxyl groups and pores significantly increased the Brønsted acid sites for the combination of H+ and N in quinoline. The hydroxyl calcium phosphate was easy to be regenerated and exhibited good recyclability for quinoline adsorption. The adsorption thermodynamics and kinetics research essentially presented the feature of the present adsorptive denitrogenation system. The newly developed adsorbent exhibited the advantages of easily modified structure, chemical stability and harmlessness for further industrial applications. [Display omitted] •Hydroxyl modified nano calcium phosphate was synthesized by a simple method.•Hydroxyl calcium phosphate obtained improved morphology and structure.•Hydroxyl calcium phosphate showed enhanced adsorption efficiency for quinoline.•Adsorption behavior was revealed via thermodynamics and kinetics studies.•Hydroxyl calcium phosphate is potentially an efficient and low-cost adsorbent.