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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. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZIF-67 were successfully modified by ultra-fine K 4 Fe(CN) 6 nanoparticles. • K 4 Fe(CN) 6 modified ZIF-67 obtained enhanced adsorption efficiency for Sr2+. • Adsorption behavior was revealed via thermodynamics and kinetics studies. • K+ introduced into ZIF-67 became adsorption sites for ion exchange with Sr2+. Development of a material with high adsorption capacity and selectivity for removal of strontium ion (Sr2+) from nuclear wastewater is a challenge. Herein, dodecahedral zeolitic imidazolate frameworks-67 (ZIF-67) was successfully modified by potassium hexacyanoferrate(Ⅱ) (K 4 Fe(CN) 6) nanoparticles, and used as an effective adsorbent for Sr2+ removal from model wastewater. In construction of adsorbent, methanol was used as the medium for assembly of ultra-fine and uniform 25 nm of K 4 Fe(CN) 6 nanoparticles on ZIF-67, well maintaining the original dodecahedral morphology and mesoporous structure of ZIF-67 crystal. N in 2-methylimidazole (2-MI) bonded with Co to generate ZIF-67, while the unsaturated Co in ZIF-67 bonded with N in K 4 Fe(CN) 6 to form spherical nanoparticles. Specific surface area of ZIF-67 were regulated by K 4 Fe(CN) 6 to an appropriate value of 607.464 m2·g−1 for Sr2+ adsorption. Adsorption efficiency of K 4 Fe(CN) 6 modified ZIF-67 for Sr2+ was significantly enhanced to 90 % within 2 h at ambient conditions, due to the improvement in morphology, structure and chemical property of adsorbent. K 4 Fe(CN) 6 modified ZIF-67 exhibited high adsorption selectivity 45 mg·g−1 for Sr2+ in the presence of competing metal ions such as K+, Na+, Mg2+ and Ca2+, and thus achieved 40 mg·g−1 of adsorption capacity for Sr2+ in actual tap water. Adsorption kinetics and isotherms were well fitted with the second-order kinetics and the Langmuir model, respectively, suggesting a chemisorption process. Mechanism studies showed that the surface of ZIF-67 was uniformly covered by ultra-fine nanoparticles, on the outer layer of which K+ ions were distributed as the adsorption sites for ion exchange with Sr2+. [ABSTRACT FROM AUTHOR]

[Display omitted] • 2D COS was firstly used to investigate the interaction between the Cr(VI) and biochars. • The response sequence of functional groups was –OH>C=O>–COOH>–CH 3. • The –COOH formed by –OH/C=O oxidation provided more Cr(III) immobilization sites. • The mechanisms of interface reaction in the adsorption system were discussed systematically. In view of the high toxicity and carcinogenicity of the Cr(VI), it is necessary to take some effective technologies to remove the Cr(VI) from the contaminated water, and the investigation into interface reaction mechanism in the process is particularly important for the technology optimization. In this study, the ZnCl 2 modified sea buckthorn stones biochar (Z-SSBC) was successfully prepared and used for removing Cr(VI) from aqueous solution, and the SEM, BET, FT-IR analyses demonstrated that the biochar possessed rough surface, large specific surface area (1031 m2/g), mesoporous structure and abundant functional groups. The maximum removal efficiency (98%) of Cr(VI) was obtained at initial pH 2 and 30 ℃, and the media pH had significant impact on the adsorption of Cr(VI) onto the Z-SSBC. The analyses of adsorption kinetics and isotherms demonstrated that the process of Cr(VI) removal by the Z-SSBC included the chemisorption and some degree of intraparticle diffusion, and the Z-SSBC exhibited the fine reusability in five adsorption–desorption cycles. The two-dimensional correlation spectroscopy (2D COS) analysis revealed the sequence of the main functional groups participating in the reaction process (–OH>C=O>–COOH>–CH 3). Furthermore, as the electron-donors, the –OH and C=O groups transform Cr(VI) anions into Cr(III), and the reduced Cr(III) ions were immobilized on the surface of the biochar. These results revealed that the prepared adsorbent had a great potential in the application of Cr(VI) removal. [ABSTRACT FROM AUTHOR]

The present work is aimed at studying the properties of α-FeOOH adsorption for removing Cr(VI) from aqueous solution. Batch adsorption experiments were carried out to measure the influences of various parameters (contact time, pH of the medium and adsorbent dosage) for Cr(VI) adsorption taking place on the α-FeOOH nanoparticles surface. Results showed that the process of Cr(VI) adsorption was strongly dependent on the pH , displaying that the adsorption efficiency of Cr(VI) reached the maximum in the pH 3 at an initial Cr(VI) load of 15 mg/L. The thermodynamic parameters such as enthalpy change (ΔH 0 ), entropy change (ΔS 0 ), Gibbs free energy (ΔG 0 ) and Isosteric heat of adsorption were also estimated. The negative value of ΔG 0 and positive value of ΔH 0 indicated a spontaneous and an endothermic thermodynamically adsorption process, respectively. The values of ΔH x demonstrated that the interaction between α-FeOOH nanoparticles and Cr(VI) was primarily physical adsorption. The adsorption process of Cr(VI) could be simulated by the pseudo-second-order kinetic equation. Intra-particle diffusion model showed that the overall adsorption rate of α-FeOOH for Cr(VI) was dominated by the film diffusion process with some degree of intra-particle diffusion. Image 1 • The as-prepared α-FeOOH nanoparticles possessed mesoporous structures and high Cr(VI) adsorption capacity. • The Cr(VI) ions adsorption onto the α-FeOOH was an integrated physico-chemical process. • The XPS analysis demonstrated that a portion of Cr(VI) was reduced to Cr(III) by the α-FeOOH at pH 3.0. [ABSTRACT FROM AUTHOR]