Yunsong Zhang

Study of the mechanisms of Cu2+ biosorption by ethanol/caustic-pretreated baker's yeast biomass

Bakers yeast biomass was pretreated by ethanol and caustic soda, and then the pristine bakers yeast, ethanol pretreated bakers yeast (ethanol-bakers yeast) and caustic soda pretreated bakers yeast (caustic-bakers yeast) were utilized as biosorbents to adsorb Cu(2+) in aqueous solution. The influence of different parameters on Cu(2+) uptake by the three biomasses, such as initial Cu(2+) concentration, initial pH of solution, contact time and temperature, was studied. The mechanism of Cu(2+) binding by biomass was investigated by a number of techniques. Evidence from potentiometric titration revealed that the concentration of carboxyl and amino groups is higher on the caustic and ethanol-bakers yeast compared to the pristine bakers yeast and FTIR spectra confirmed carboxyl, and amino groups on the surface of bakers yeast could be available for characteristic coordination bonding with Cu(2+). In addition, SEM and Zeta potential of the three samples show that caustic and ethanol-pretreatment resulted in the change of bakers yeast surface structure and charge which is relative to adsorption. These results demonstrate that the increase of biosorption capacity for Cu(2+) by ethanol and caustic-bakers yeast was attributed to the increase and exposure of carboxyl and amino groups on the surface of biomass sample.

Facile synthesis of hydroxyapatite/yeast biomass composites and their adsorption behaviors for lead (II).

For the first time, the hydroxyapatite (HAp)/yeast biomass composites were successfully synthesized through a facile alkaline ultrasound cavitation method, and used as a novel sorbent for removal of Pb(2+) from aqueous solution. The obtained HAp/yeast biomass composites were characterized by various techniques, including SEM, EDX, XRD, TGA, FTIR, XPS and fluorescence detection, respectively. It was found that the yeast cells were wrapped by the well-dispersed HAp, and more functional groups (such as carboxyl, hydroxyl and amino) on yeast surface were exposed. Also, varying factors that may affect the adsorption efficiency of HAp/yeast biomass composites, such as solution pH, reaction temperature and time, have been carefully investigated respectively. Remarkably, more than 99% of Pb(2+) can be removed by the HAp/yeast biomass composites. Evidence from FTIR and XPS analysis revealed that the higher removal efficiency should be ascribed to the synergetic effect of synthesized HAp and more functional groups exposed on yeast surface.

Difference between Pb and Cd accumulation in 19 elite maize inbred lines and application prospects

In the last two decades, the accumulation of heavy metal in crop grains has become the study hotspot. In this study, 19 representative elite maize inbred lines and 3 hybrid varieties were investigated at the seedling stage, which can accumulate Pb and Cd in the stems and leaves, respectively. The results demonstrated that significant differences are among inbred lines for accumulation of heavy metals, implying that the Cd accumulation is significant correlation between the male parents and their hybrids and some inbred lines have been selected for cross-breeding with low Pb or Cd accumulation, such as S37, 9782, and ES40; Moreover, some inbred lines could be suitable for phytoremediation species for soil bioremediation with high levels of Pb and Cd accumulation, including 178, R08, 48-2, and Mo17ht.

Fabrication of a three-dimensional porous Z-scheme silver/silver bromide/graphitic carbon nitride@nitrogen-doped graphene aerogel with enhanced visible-light photocatalytic and antibacterial activities

A novel three-dimensional (3D) porous Z-scheme silver/silver bromide/graphitic carbon nitride@nitrogen-doped graphene aerogel (Ag/AgBr/g-C3N4@NGA) photocatalyst was successfully fabricated by a facile hydrothermal and freeze-drying method, and its photocatalytic degradation performance and inactivation effects were also evaluated. The series of characterization results certified that the obtained Ag/AgBr/g-C3N4@NGA synergistically integrates the structural and functional advantages of the Ag/AgBr species and g-C3N4 into the 3D macroscopic porous nitrogen-doped graphene aerogel (NGA) with high conductivity. Benefiting from a unique composition and structure, the obtained Ag/AgBr/g-C3N4@NGA exhibited excellent photocatalytic degradation efficiency for methyl orange (MO), approximately 96% after 30 min of visible-light illumination, which was approximately 1.7 times higher than that of a graphitic carbon nitride@nitrogen-doped graphene aerogel (g-C3N4@NGA). Meanwhile, Ag/AgBr/g-C3N4@NGA possessed high photodegradation efficiency for bisphenol A (BPA), approximately 92% within 120 min. Based on the underlying premise of maintaining the original morphology, the mass loss of Ag/AgBr/g-C3N4@NGA is below 5%, and its excellent photocatalytic performance was also well maintained after eight cycles. Moreover, Ag/AgBr/g-C3N4@NGA has a disinfection effect on E. coli (approximately 6 log inactivation) and S. aureus (approximately 1.2 log inactivation) in 60 min of visible-light illumination, and an excellent disinfection effect on E. coli was maintained after five applications.