Fixed-bed adsorption of the dye Chrysoidine R on ordered mesoporous carbon

Funding: The authors are grateful to the Ministry of Human Resource Development of the Government of India for financial support through the SPARC initiative (project: SPARC/2018-2019/P307/SL). One of the authors (AM) is thankful to MANIT, Bhopal for providing fellowship support.Herein, the efficiency of an ordered mesoporous carbon (OMC), synthesized through metal and halide free pathways, is evaluated to remove an anionic dye Chrysoidine R through fixed-bed adsorption. Potentially toxic azo dye, Chrysoidine R, was employed as a test and encouraging results are obtained. The bulk removal of the dye was accomplished with 99.77% column saturation and treatment of the exhausted bed of adsorbent with a suitable eluent resulted in almost 100% dye-recovery. The efficiency of the column remained almost unchanged in five adsorption/desorption cycles. The fixed-bed column studies clearly reveal that the OMC is a highly efficient and robust material for large-scale wastewater treatment applications.Publisher PDFPeer reviewe

Batch and bulk adsorptive removal of anionic dye using metal/halide-free ordered mesoporous carbon as adsorbent

The authors are grateful to the Ministry of Human Resource Development of the Government of India for financial support through the SPARC Project- SPARC/2018–2019/P307/SL. One of the authors (Asna Mariyam) is also grateful to MANIT, Bhopal for providing fellowship assistance. We thank the University of St Andrews for a PhD scholarship for FS. We acknowledge EPSRC Strategic Resources Grant (EP/R023751/1).The present report is an outcome of investigations to assess the adsorptive potential of a synthesized metal- and halide-free variant of ordered mesoporous carbon (OMC) towards an anionic azo dye, Methyl Orange. The results of preliminary studies, carried out in batch mode, helped in setting up the process variables to achieve optimum adsorption conditions. The experimental data were then fitted to Langmuir, Freundlich, Temkin, and Dubinin-Radushkevitch isotherm models. The equilibrium data fitted well to the Langmuir model at 303 K and the monolayer adsorption capacity was 0.33 mmol g−1. The adsorption kinetics were explored by fitting the data to pseudo-first-order and pseudo-second-order kinetic models. The latter described the kinetics well, as indicated by higher regression coefficients. To elucidate the mechanism of mass transfer, various well-known mathematical models were employed. The adsorption of the dye was found to involve particle diffusion. Thermodynamic studies revealed that the adsorptive uptake of Methyl Orange by the OMC was spontaneous (ΔG0 = −23.71 kJ mol−1) and exergonic (ΔH0 = −123.15 kJ mol−1). Finally, the bulk removal of the anionic dye was investigated through column operations followed by column regeneration (desorption) studies. Column saturation of up to 96.55% could be realized. Values for dye recovery reached up to 93.26%. The column efficiency was then evaluated by carrying out three consecutive adsorption/desorption cycles. The results obtained indicated that the adsorbent has a good ability to eliminate Methyl Orange from wastewater, both in batch and column operations.PostprintPeer reviewe

Adsorption behaviour of Chrysoidine R dye on a metal/halide-free variant of ordered mesoporous carbon

The paper reports the removal of Chrysoidine R, a toxic mono-azo dye from its aqueous solution by employing metal- and halide-free variant of ordered mesoporous carbon as adsorbent in batch experiments. The influence of various parameters such as hydronium ion concentration, adsorbent dosage, initial dye concentration, exposure time on dye uptake was studied. The process could be described by Langmuir, Freundlich and Dubinin-Radushkevitch isotherm models. Evaluation of thermodynamic variables proved that the adsorption was spontaneous, feasible and endothermic. The kinetics involved in the process was worked out using pseudo-first-order and pseudo-second-order kinetic models. The latter was found appropriate for the analysis of the experimental data. The mechanism governing the overall adsorption was elucidated with the aid of various mathematical models. The adsorption was found to proceed via film diffusion with chemisorption being the rate-determining step. The complete removal of dye with fast removal rate makes the material propitious in the field of water treatment

Efficient batch and fixed-bed sequestration of a basic dye using a novel variant of ordered mesoporous carbon as adsorbent

Herein, an ordered mesoporous carbon (OMC) material was prepared using a metal and halogen free method, and its adsorptive potential for the cationic dye, ‘Methylene Blue’ (MB), was investigated. Batch studies were carried out to determine the influence of pH, dye concentration, adsorbent quantity, and contact time on adsorption behaviour. Adsorption models based on Langmuir, Freundlich, Temkin and Dubinin-Radunkevich isotherms were validated and the thermodynamic variables governing the nature and feasibility of reaction were evaluated. Values of the adsorption uptake at equilibrium (qe) decreased as the temperature was increased, suggesting thereby that the adsorption process involved was exothermic. Kinetic studies indicated that adsorption obeyed pseudo-second order behaviour and operated via a ‘film-diffusion’ mechanism. When attempts were made to carry out bulk removal of MB using a fixed bed adsorption column, 99.5% saturation could be achieved. Desorption of MB from the used column was performed and dye recovery was almost 100% in the first cycle and on 5th cycle 99% of dye was obtained. This pattern clearly indicates that for the cationic dye MB, OMC acts as a highly efficient and robust adsorbent.</p