Crop Residue Ashes as Adsorbents for Basic Dye (Methylene Blue) Removal: Adsorption Kinetics and Dynamics

Abstract

In the quest for identifying low‐cost, locally available and effective adsorbents, pigeon pea (Cajanus cajan L.) residue ash (PRA) and sunflower (Helianthus annuus L.) residue ash (SRA) were evaluated as adsorbents for sequestering a basic dye, methylene blue (MB), from aqueous solution. Effects of contact time, initial solution pH and adsorbent dose on MB adsorption were investigated. MB adsorption onto PRA and SRA was dependent on initial solution pH, with adsorption being greater at higher pH. Percent MB removal increased with increase in adsorbent's dose. Adsorption followed pseudo‐second order kinetics. Intraparticle diffusion was not the sole rate‐controlling step. Both film diffusion and intraparticle diffusion controlled the adsorption process. The equilibrium data fitted well to Langmuir isotherm as compared to Freundlich isotherm, on the basis of coefficient of determination and error analysis. The maximum MB adsorption capacities of PRA and SRA were found as 58.8 and 62.5 mg g−1, respectively. The free energy change and dimensionless equilibrium parameter revealed spontaneous and favorable nature of MB adsorption onto crop residue ashes. Results demonstrate that the PRA and SRA have high adsorptive potential as compared to many previously reported ash based adsorbents, and hence can be used for treating water contaminated with cationic dyes.

Removal of methylene blue from aqueous system using tobacco stems biomass: Kinetics, mechanism and single‐stage adsorber design

“…The Langmuir isotherm parameters, maximum adsorption capacity ( b ) and bonding energy constant ( k ) were estimated as 169.5 mg g −1 and 0.022 L mg −1 , respectively. Further, the R L value for MB adsorption on TSB was found to be positive and less than unity (0.154), indicating favorable (0 < R L < 1) adsorption process . A comparison of adsorption capacity of different adsorbents shows that TSB for MB was found substantially superior to that of many reported low‐cost adsorbents (Table ).…”

“…The ΔG value for MB adsorption onto TSB was −5.26 kJ mol −1 at room temperature (27 ± 1 ° C), indicating a spontaneous and favorable process of MB adsorption onto TSB. Further, this Δ G value is within the range (0 to −20 kJ mol −1 ) of free energy change for physi‐sorption and hence, MB adsorption onto TBS was by physi‐sorption.…”

“…The pH ZPC of TSB, used in this study, was 4.74. When pH e of the system (i.e., for initial solution pH 5 and above), was higher than the pH ZPC of TBS, the sorbent's surface negative charge density increased, and resulted in high MB adsorption [4,9].…”

“…That is why the application of activated carbon for wastewater treatment in developing countries is still limited. This has prompted an exploration of renewable alternative adsorbents, especially of plant origin like coir pith carbon , coconut bunch waste , sugarcane bagasse , Typha phytomass , Eichhornia crassipes biomass , crop residue ash , etc. Local availability, abundance, little/no processing and low cost are some obvious advantages of plant biomass based adsorbents.…”

Optimization of process parameters for methylene blue removal by jute stick using response surface methodology

“…The reason is that increase in dye concentration facilitates higher interaction between MB and JS. Further, higher initial dye concentration facilitates to overcome the resistance to mass transfer of MB between the adsorbent and aqueous phase [18,22,41]. The study indicated that under the studied levels of time, there was no significant difference among treatments after 60 min.…”