A simple chemical method for the synthesis of Cu^(2+) engrafted MgAl_(2)O_(4) nanoparticles: Efficient fluoride adsorbents, photocatalyst and latent fingerprint detection

An adaptable, energy efficient chemical process is employed to synthesize Cu^2+engrafted MgAl2O4 nanoparticles(Mg1-xCuxAl2O4, x = 0, 0.1, 0.3, 0.5 abbreviated as MCA0, MCA1, MCA3,and MCA5 respectively), using chelating ligand and the calcination temperature was determined by the thermogravimetric analysis of the precursor mass.They acted as good fluoride adsorbent in the presence of co-ions, different pH(2–11) via chemisorption revealed from Fourier-transform infrared spectroscopy(FTIR) and photodegraded Methylene Blue(MB).The satisfactory results were for MCA1(specific surface area 25.05 m^2/g) with 97%fluoride removal at pH 7.0 for the 10 mg/L initial fluoride concentration for 1.5 g/L adsorbent dose with 45 min contact time obeying the Langmuir isotherm model with negative thermodynamic parameters and 4 mmol of MCA3 with 98.51% photodegradation for 10-5 mol/L MB solution obeying pseudo-second-order and pseudo-first-order kinetics respectively.The proposed photodegradation mechanism of MB was established by the FTIR and high-performance liquid chromatography(HPLC) analysis.The nanoparticles are cubic, estimated through X-ray diffraction(XRD) and transmission electron microscopy(TEM) analysis.The band gap energies, grain size, and the effective working pH were estimated by diffuse reflectance spectra(DRS), scanning electron microscope(SEM), and zero-point potential analysis respectively.A soil candle with MCA1 also fabricated for the household purpose and tested with some fluorinated field samples.The MCA3 was able to enhance the latent fingerprint on smooth surfaces.

Effects of fluoride on the removal of cadmium and phosphate by aluminum coagulation

This study focuses on the effects of p H and fluoride at different molar ratios of fluoride to Al（R F：Al） on the removal of cadmium（Cd^（2＋）） and phosphate by Al coagulation. Fluoride at R F：Al≥ 3：1 inhibits the removal of Cd over wide Al dose ranges from 5 to 10 mg/L as Al. The removal of phosphate decreases significantly at high R F：Al of 10：1 whereas at lowered R F：Al（i.e., ≤ 6：1）, an adverse effect is observed only at insufficient Al doses below 2 mg/L. Fluoride shows inhibitive effects towards the removal of Cd at p H 7 and 8 and that of phosphate at p H 6. Fluoride decreases the ζ-potential in both systems, and the decreasing extent is positively correlated to the elevated R F：Al. The Al fluoride interactions include the formation of Al-F complexes and the adsorption of fluoride onto Al（OH）3 precipitates, i.e., the formation of Al（OH）n F m. Al-F complex formation inhibits Al hydrolysis and increases residual Al levels, and a more significant increase was observed at lower p H. Al-F complexes at high R F：Al complicate the coagulation behavior of Al towards both negative and positive ionic species. Moreover, fluoride at low R F：Al shows little effect on Al coagulation behavior towards Cd^2＋and phosphate, and the spent defluoridation adsorbent,i.e., aluminum（Al） hydro（oxide） with adsorbed fluoride at R F：Al of below 0.1：1, may be reclaimed as a coagulant after being dissolved.