This work investigates the production of activated lignin-chitosan extruded (ALiCE) pellets with controlled particle size distribution (almost spherical: dp ~500-1000µm) for efficient methylene blue adsorption. The novel preparation method employed in this study successfully produced activated lignin-chitosan pellets. Structural and morphological characterizations were performed using BET, FTIR and SEM-EDX analyses. The influence of contact time, solution 17 pH, ionic strength, initial adsorbate concentration and desorption studies was investigated. The 18 experimental data fitted well with the Langmuir isotherm (R 2 = 0.997), yielding a maximum adsorption capacity of 36.25mg/g. The kinetic data indicated that methylene blue (MB) adsorption onto ALiCE can be represented by the pseudo second-order-model with intraparticle processes initially controlling the process of MB adsorption. Overall, these results indicate that the novel ALiCE offers great potential for removing cationic organic pollutants from rivers and streams.
With most recent studies being focused on the development of advanced chemical adsorbents, this paper investigates the possibility of using two natural low-cost materials for selective adsorption. Multi-adsorbent systems containing tea waste (TW) and dolomite (DO) have been tested for their effectiveness in the removal of copper and methylene blue from aqueous solutions. The effects of contact time, solution pH and adsorption isotherms on the sorption behaviour were investigated. The Langmuir and Freundlich isotherms adequately described the adsorption of copper ions and methylene blue by both materials in different systems. The highest adsorption capacities for Cu and MB were calculated as 237.7 mg/g at pH 4.5 and 150.4 mg/g at pH 7 for DO and TW:DO respectively. Tea waste and dolomite were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and Energy dispersive X-ray analysis. The removal of Cu and MB by dolomite was mainly via surface complexation while physisorption was responsible for most of the Cu and MB adsorption onto tea waste. Identifying the fundamental mechanisms and behaviour is key to the development of practical multi-adsorbent packed columns.
The biosorption process of anionic dye Alizarin Red S (ARS) and cationic dye methylene blue (MB) as a function of contact time, initial concentration and solution pH onto olive stone (OS) biomass has been investigated. Equilibrium biosorption isotherms in single and binary systems and kinetics in batch mode were also examined. The kinetic data of the two dyes were better described by the pseudo second-order model. At low concentration, ARS dye appeared to follow a two-step diffusion process, while MB dye followed a three-step diffusion process. The biosorption experimental data for ARS and MB dyes were well suited to the Redlich-Peterson isotherm. The maximum biosorption of ARS dye, qmax = 16.10 mg/g, was obtained at pH 3.28 and the maximum biosorption of MB dye, qmax = 13.20 mg/g, was observed at basic pH values. In the binary system, it was indicated that the MB dye diffuses firstly inside the biosorbent particle and occupies the biosorption sites forming a monodentate complex and then the ARS dye enters and can only bind to untaken sites; forms a tridentate complex with OS active sites.
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