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Cellolignin, a by-product from the wood processing industry, was studied as a new, eco-friendly adsorbent for the removal of methylene blue cationic dye from aqueous solutions, using a batch adsorption procedure. Experimental data were processed in order to study the equilibrium, thermodynamics, and kinetics of methylene blue adsorption onto cellolignin. Between the two studied isotherm models (Freundlich and Langmuir) the Langmuir model better described the equilibrium adsorption data at temperatures higher than 25 °C; the mean free energy (E) values obtained from the Dubinin-Radushkevich isotherm model show that the sorption of dye occurs via surface electrostatic interactions with the active sites of the cellolignin. The equilibrium data were used to calculate the free energy, enthalpy and entropy changes, and isosteric heat of adsorption (ΔH X ). Results confirm the feasibility and the endothermic nature of the adsorption process, suggesting that adsorption is a physico-chemical process. The isosteric heats of adsorption indicated energetic heterogeneity of adsorption sites and possible interactions between the adsorbed dye molecules. Kinetic assessment suggests that the adsorption process followed a pseudosecond order model and the rate-limiting step may be the binding of dye onto the adsorbent surface. The diffusion models show that intraparticle diffusion is not the sole rate-limiting step; the external mass transfer also influences the adsorption process in its initial period.

In this work, the use of an agro-industrial waste, i.e., sunflower seed shells, was investigated as a sorbent for the removal of Orange 16 reactive dye from aqueous environments. Batch experiments were performed as a function of pH, sorbent dose, dye concentration, temperature and contact time. The percent dye removal increased with increasing sorbent dose and temperature of the aqueous solution, and decreased with increasing dye concentration; the required contact time was five hours. The Freundlich, Langmuir, Dubinin-Radushkevich and Tempkin adsorption isotherms were used to describe the equilibrium sorption data and to determine the corresponding isotherm constants. The thermodynamic parameters ?G, ?H and ?S were also determined. These parameters indicated that the sorption of reactive dye onto sunflower seed shells was a spontaneous, endothermic and entropy-driven process. The kinetic data were evaluated by pseudo-first order, pseudo-second order and intra-particle diffusion kinetic models. The results of the kinetic study indicated that the sorption of Orange 16 reactive dye onto sunflower seed shells is a complex process and both chemical surface sorption and intraparticle diffusion contribute to the rate-limiting step. Therefore, the sunflower seed shell showed itself to be a promising cheap sorbent for the decolourization of aqueous coloured solutions or effluents.

Abstract:© Versita Sp. z o.o. The sorptive potential of some lignocellulosic agro-industrial wastes (sunflower seed shells and corn cob) for Basic Blue 9 cationic dye removal from aqueous solutions was examined using the batch technique. The Freundlich, Langmuir, and Dubinin-Radushkevich isotherm models were used in order to determine the quantitative parameters of sorption. The Langmuir isotherm model indicated a maximum sorption capacity for these materials in the range of 40-50 mg dye per g (25 o C), slightly higher for corn cob than for sunflower seed shells. The values of the thermodynamic parameters showed that the retention of cationic dye is a spontaneous and endothermic process. The application of pseudo-first order and pseudo-second order intraparticle diffusion models, and a BoydReichenberg model for kinetic data interpretation suggested that sorption of Basic Blue 9 dye onto the studied materials is a process where both surface sorption and intraparticle diffusion contributed to the rate-limiting step. These lignocellulosic wastes can be used with good efficiency for dye removal from aqueous effluents.

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Cd(II) plus iodide species were extracted into PEG-rich phases in the aqueous PEG(1550)-(NH 4 ) 2 SO 4 system at pH 2.05 -7.12. IR spectra show that increasing (NH 4 ) 2 SO 4 solution acidity does not protonate PEG ether oxygen atoms, but decreases water content in the PEG-rich phases. Metallic species' extraction into the PEG predominantly alters how water molecules bind to polymer chains; the changes in their absorption bands depend on pH. Microscopy shows that "fixation" of the extracted metal in the PEG-rich phase occurs by specific interactions which depend on the species. These also determine changes in the polymer chains' conformation.

The biosorption Brilliant Red HE-3B reactive dye by nonliving biomass, Saccharomyces cerevisiae, in batch procedure was investigated. Equilibrium experimental data were analyzed using Freundlich, Langmuir and Dubinin — Radushkevich isotherm models and obtained capacity about 104.167 mg g−1 at 20°C. The batch biosorption process followed the pseudo-second order kinetic model. The multi-linearity of the Weber-Morris plot suggests the presence of two main steps influencing the biosorption process: the intraparticle diffusion (pore diffusion), and the external mass transfer (film diffusion). The results obtained in batch experiments revealed that the biosorption of reactive dye by biomass is an endothermic physical-chemical process occurring mainly by electrostatic interaction between the positive charged surface of the biomass and the anionic dye molecules. The biosorption mechanism was confirmed by FT-IR spectroscopy and microscopy analysis