ABSTRACT
Chitosan-modified biochar ï¼CBCï¼ was prepared as a low-cost and highly efficient adsorbent for Cd2+ in aqueous solutions. Batch adsorption experiments were conducted to evaluate the adsorption performance. Characterization experiments with SEM-EDSï¼ FTIRï¼ and XPS were used to analyze the surface microstructure and chemical composition of the adsorbent. The results showed that the adsorption performance of CBC was remarkably improved by the introduction of surface functional groups ï¼-OHï¼ -C=Oï¼ and -NH2ï¼. The pseudo-second-order kinetic model and Langmuir model were better for describing the kinetics and isotherms for Cd2+ adsorption onto CBCï¼ indicating that the adsorption rate was determined by the active sites and controlled by monolayer chemisorption. The adsorption process was endothermic spontaneousï¼ and the key mechanisms involved complexationï¼ precipitationï¼ cation exchangeï¼ and cation-π bonds. After five instances of adsorption-desorption cyclesï¼ the adsorption capacity of CBC for Cd2+ still remained above 80% of the initial adsorption capacityï¼ indicating that CBC had a favorable recyclability. The current work embodies the concept of green chemistryï¼ and the prepared chitosan-modified biochar was a promising adsorbent for the removal of Cd2+ in wastewater and soil.
ABSTRACT
A Gram-positive, moderately halophilic, motile, strictly aerobic, endospore-forming, oxidase- and catalase-positive, rod-shaped bacterium, strain YIM kkny16(T), was isolated from a saline mud sample collected from the Keke salt lake in the Qaidam Basin, north-west China. This isolate grew in the presence of 0-25 % (w/v) NaCl and at pH 6.0-10.0 and 10-50 degrees C; optimum growth was observed with 10 % (w/v) NaCl and at pH 7.0 and 37 degrees C. Strain YIM kkny16(T) had meso-diaminopimelic acid as the diagnostic diamino acid, MK-7 as the predominant respiratory quinone, with a significant amount of MK-6, and anteiso-C(15 : 0), iso-C(14 : 0) and C(16 : 1)omega7c alcohol as major fatty acids. Major polar lipids were diphosphatidylglycerol and phosphatidylglycerol. The DNA G+C content was 41.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences confirmed that strain YIM kkny16(T) was a member of the genus Virgibacillus, exhibiting sequence similarities of 94.9-97.3 % to the type strains of recognized Virgibacillus species. Strain YIM kkny16(T) could be differentiated from recognized Virgibacillus species based on phenotypic characteristics, chemotaxonomic differences, phylogenetic analysis and DNA-DNA hybridization data. On the basis of evidence from this polyphasic study, strain YIM kkny16(T) is considered to represent a novel species of the genus Virgibacillus, for which the name Virgibacillus kekensis sp. nov. is proposed. The type strain is YIM kkny16(T) (=DSM 17056(T)=CGMCC 1.6298(T)).