C. Srinivasakannan

Efficient cleaning extraction of silver from spent symbiosis lead-zinc mine assisted by ultrasound in sodium thiosulfate system

The process to fast recovery of silver from the spent symbiosis lead-zinc mine enhanced by ultrasound has been developed. A system composed of thiosulfate and the spent symbiosis lead-zinc mine under ultrasound radiation is researched and compared with regular methods to prove the superiority of ultrasound enhanced leaching. Oxygen is not provided by the usual way but by the cavitation of ultrasound, and the effect of ultrasonic enhanced leaching is more obvious than oxygen enhanced leaching effect. We are more authoritative by combining some valuable literature after conducting systematic experiments. The process mechanism was analyzed by fire assaying, XRD, XRF, SEM and EDS. The optimal conditions were found out through single factor experiments: stirring rate of 300u202frpm, thiosulfate concentration of 75u202fg/L, leaching temperature of 303u202fK, PH of 5, leaching time of 2u202fh and the ultrasound power of 100u202fW. And the leaching rate is 77.34% under the best conditions. When the ultrasonic experiment has the same parameters as the normal, the leaching rate at five minutes under ultrasonic conditions was 73.88%, while the leaching rate was only 72.51% at two hours under normal conditions. The apparent activation energy under conventional and ultrasonic conditions is 12.47u202fkJ/mol and 12.35u202fkJ/mol, respectively, and it is proved that both are controlled by diffusion.

Preparation and application of phosphinic acid functionalized nanosilica for the effective removal of mercury (II) in aqueous solutions

AbstractA novel adsorbent was synthesized by functionalizing nanosilica with phosphinic acid groups for the removal of mercury ions from aqueous solutions. The synthesized absorbent was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM) and thermogravimetric analysis (TGA). Meanwhile, the effects of initial pH, contact time and initial mercury ions concentration on the removal of mercury ions from aqueous solutions were investigated by batch adsorption experiments. The results showed that the removal rate reached 99.11% and the maximum adsorption capacity was up to 274.32u2009mg/g at pH 2 and the equilibrium time of adsorption was about 1u2009h. The absorbent presented good selectivity for mercury ions among Zn(II), Ni(II), Mn(II) and Ge(IIII). Moreover, the obtained adsorbent has good reusability and the absorbability decreased only from 98.76 to 94.75% after five cycles. Besides, the adsorption isotherms fitted well to the Langmuir isotherm model and adsorption kinetics followed the pseudo-second-order model. The removal mechanism of mercury via phosphinic acid-functionalized silica nanoparticles was chelation interaction. All the experimental data indicated that the phosphinic acid-functionalized silica nanoparticles are very promising in removal of mercury ions from aqueous solutions.n A novel adsorbent was synthesized by functionalizing nanosilica with phosphinic acid groups for the removal of mercury ions from aqueous solutions. The adsorbent presented good selectivity and reusability. The removal mechanism is chelation interaction between mercury ions and PA-SNPs.HighlightsA new adsorbent was prepared via modifying nanosilica with phosphinic acid groupsThe adsorbent exhibits an excellent selectivity for mercury ionsThe adsorbent showed a maximum adsorption capacity of 274.32u2009mg/g for mercury ions under pH 2The removal mechanism was chelation interaction.