Evaluation of different isotherm models, kinetic, thermodynamic, and copper biosorption efficiency of Lobaria pulmonaria (L.) Hoffm

Synthesis and characterization of chitosan-vermiculite-lignin ternary composite as an adsorbent for effective removal of uranyl ions from aqueous solution: Experimental and theoretical analyses

Chitosan (Ch), vermiculite (V) and lignin (L) were used as the components of a natural composite adsorbent (Ch-VL) for the removal of the UO₂²⁺ ions in aqueous solutions. During the study, we recorded and analyzed the initial UO₂²⁺ ion concentration, initial pH, contact time, temperature, and recovery. The recycling performance of the Ch-VL composite was assessed by three sequential adsorption/desorption experiments. Adsorption performance of the Ch-VL composite for UO₂²⁺ ions was 600 mg L^-1 at pH 4.5 and temperature of 25 °C. Thermodynamic findings, ΔH⁰:28.1 kJ mol^-1, and ΔG⁰:-14.1 kJ mol^-1 showed that adsorption behavior was endothermic and spontaneous. Its maximum adsorption capacity was 0.322 mol kg^-1, obtained from the Langmuir isotherm model. The adsorption kinetics indicated that it followed the pseudo-second-order and intraparticle diffusion rate kinetics. The adsorption thermodynamic shown indicated that the UO₂²⁺ ion adsorption was both spontaneous and endothermic. The adsorption process was enlightened by FT-IR and SEM-EDX analyses. The study suggested a simple and cost-effective approach for the removal of toxic UO₂²⁺ ions from wastewater. To highlight the adsorption mechanism, DFT calculations were performed. Theoretical results are in good agreement with experimental observations.

Determination of the effect of RBBR on laccase activity and gene expression level of fungi in lichen structure

This study provides information about the differential transcription regulation of laccase genes in response to RBBR dye. To this purpose, we determined the laccase gene expression, laccase activity, and protein profile of lichen-forming fungi supported to RBBR dye. For those obtained from optimal laccase genes expression profiles, we modified different RNA extraction protocols to obtain high quality and quantity RNA to be used in downstream applications in lichen-forming fungus. We also determined the expression of ten laccase genes in response to RBBR dye by qRT-PCR and validated protein profile. As a result of our study, a high laccase activity of 522 U mL^-1 was obtained after submerged fermentation for 17 days. The maximal laccase activity to RBBR dye was obtained at 408 h. The expression profiles of laccase gene expression on ten laccase genes showed up- or down-regulation in course of eight fermentation times. The most up-regulated gene during the process was lac8. However, poxa1b gene expression was lowest in lichen-forming fungi biomass supplemented with RBBR dye. This study has revealed the influence of RBBR dye on laccase activity levels and the determination of gene expression levels in lichen-forming fungi.

Biosorption of Cu2+ and Ni2+ Ions from Synthetic Waters

In this study, biosorption of Cu²⁺ and Ni²⁺ ions to tobacco stalks was investigated under different operational conditions. The effects of the initial pH, ion concentrations, temperature, and duration of contact and adsorbent dosage were determined in the batch experiments. Chemical oxygen demand (COD) analyses were also performed to identify the possible negative effects of the sorbent throughout biosorption process. The sorption capacities of this sorbent were predicted by use of the equilibrium and kinetic models. Within the scope of kinetic study, it was observed that biosorption fitted to second-order pseudo kinetic rate expression. The highest R ² value in isotherm studies was obtained from Freundlich isotherm (R ² = 0.9940-0.9929) for the inlet concentration. FTIR, SEM, and EDX analyses were performed to investigate the surface characteristics and chemical structure of the biosorbent. Under optimum conditions, qe value for Cu²⁺ was determined as 7.18 mg/g and removal efficiency was 86.24%; qe value for Ni²⁺ was determined as 6.45 mg/g and removal efficient was 77.4%. Sorbent recovery process was also performed within the scope of this study with 0.1 M H₂SO₄, 0.1 M HCl, and distilled water. A significant decrease was observed in efficiency when the recovered sorbent was reused.