Cellulose-based nanocomposite (FeCNB) has been synthesized via sol-gel conversion for adsorptive remediation of Congo red, a carcinogenic and mutagenic azo dye, from water. The bead was characterized by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDAX) and transmission electron microscopy (TEM). The effect of adsorbent dose, pH, contact time, shaking speed, initial dye concentration and temperature was carried out in a batch adsorption study. The maximum removal of Congo red was found at pH 6.0, corresponding to the adsorbent dose of 1.0 gdm-3 and 90 min of contact time. The experimental data were analyzed using different isotherm and kinetic models. The data was fitted best to Langmuir isotherm model and pseudo-second-order kinetic model. The maximum adsorption capacity evaluated from Langmuir isotherm is 3.52 mgg-1 at 303 K. Thermodynamic study was carried out to evaluate the changes in Gibbs free energy (ΔG0 ), enthalpy (ΔH0 ) and entropy (ΔS0 ) of the dye-adsorbent interaction. The negative ΔG0 values at all temperatures suggested the spontaneous nature; the positive ΔH0 value indicated the endothermic nature and the positive ΔS0 indicated the increased randomness of the adsorption process. Desorption study found 0.1 (M) NaOH as the most suitable eluting agent for dye-loaded adsorbent. The adsorbent can be used up to five successive cycles of adsorption-desorption.
In the present world scenario the demand for fresh water and clean energy is driving the need to convert a microbial fuel cell (MFC) into an algal-based microbial desalination cell (MDC) that can support algal growth along with desalination of saline water. In this study, the performance of a five-chambered MDC fed with saline water having two different salt concentrations, namely 2.5 g/L and 5.0 g/L in desalination chamber, as well as MDC operated without algae in catholyte was investigated. The algal-based MDC operated with 5 g/L of total dissolved solid (TDS) in desalination chamber exhibited the best performance results among all other combinations giving a maximum power density of 45.52 mW/m2 and a desalination efficiency of 71 ± 2 %. Also, a chemical oxygen demand (COD) removal efficiency of 78 % and coulombic efficiency of 12.24 % was achieved with 5 g/L NaCl concentration in desalination chamber. Based on this experimental performance evaluation, it can be inferred that algal-based MDC can provide a promising and sustainable approach for wastewater treatment with the capability of simultaneous desalination, algal production and electrical energy recovery.
Iron(III) loaded cellulose nanocomposite bead, synthesized through sol-gel method, was characterized by Fourier transform infra-red spectroscopy, field emission scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, tunneling electron microscopy, and tested for adsorptive removal of alizarin red S from aqueous solution. The influence of variables such as pH, contact time, initial dye concentration, adsorbent dose and temperature for dye retention were investigated in batch operation. The process was optimized by employing response surface methodology following full factorial and central composite design. The maximum adsorption of 97% was observed at an optimum condition of pH 3.0, dose of 2.0 gdm-3 and shaking time of 45 mins corresponding to the dye concentration of 100 mgdm-3 at 303 K. Correlation of cooperative influences of the significant variables and the extent of dye adsorption were represented by a second order polynomial equation. The mutual interactions of the significant variables were presented by 3D response surface and 2D contour plots in the design space. The adsorption was better described by Langmuir isotherm and pseudo second order kinetics. The process was spontaneous (-∆G°, 48.19 kJmol-1 ), feasible (∆S°, 0.284 Jmol -1 K-1 ) and endothermic (∆H°, 71.62 kJmol-1 ). The adsorbent can be regenerated with NaOH (10.0 × 10-2 M) and recycled for reuse, at least for five successive operations.
Unfixed dyes released from various industries directly impact on the environment quality which is quite alarming and a matter of concern. In the present study, the removal of a carcinogenic azo dye, congo red (CR), was modelled for column adsorption dynamics following batch study in aqueous solution using iron modified cellulose nanobead. The effect of process parameters has been described for both batch and column study. Adsorption capacity of CR in the batch mode and column mode was calculated to be 3.29 and 8.69 mg g−1 respectively. The elution of retained CR from FeCNB phase was performed using 1.0 x 10-1 mol dm-3 NaOH and the maximum elution was found to be 81.25%. The experimental data were well described by BDST model.
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