Removal of Methylene Blue From Water Using Non‐Modified Date Seed as Bio‐Adsorbents: A Green and Sustainable Approach

Abstract

Methylene blue (mb) is a synthetic dye used in many industries due to its unique color and characteristics. Due to its usage on a large scale substantial amounts of this dye are constantly released into different environmental compartments, which have posed severe threats to the environment. As effective adsorbent has been developed for the remediation of this dye in the current study using Date Seed Biomass Precursors (DBP); a green biosorbent having low cost and is eco‐friendly that will pose no hazardous effects on the environment. The DBP was characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy. SEM studies reveal that the surface of DBP is rough and porous whereas the FTIR revealed the presence of various functional groups responsible for the electrostatic interactions and ion exchange, and so forth as required for the removal of mb from aqueous media. The pH PZC of the DBP was determined using the Drift Method. The pH PZC was found to be 6. The optimum conditions for the remediation of mb were; pH = 8, and DBP dosage = 0.5 g/50 mL of mb solution at 298 K. According to the validation of kinetic data, pseudo 2nd order kinetics has fully explained the kinetics data with R 2 value of 0.997 and Q calculated value of 3.87 mgg −1 , while, the adsorption isotherm data of the mb was well expressed by the Langmuir model with the value of R 2 = 0.9923 and q m = 12.106 mgg −1 . The Q calculated from kinetics adsorption data and isotherm adsorption data was approximately equal to the Q Experimental data of kinetics and adsorption data. Various thermodynamic parameters were calculated using Vant Hoff equation. The values of Gibbs free energy (Δ G ○ ) at tested temperatures from low to high were: −5.035 kJ/mol, −6.430 kJ/mol, −6.715 kJ/mol and −7.330 kJ/mol, the indicative requirements of spontaneous and feasible process. The positive value of entropy (Δ S ○ ) 123 kJ/mol confirmed the high affinity and structural compatibility of DBP and mb. The loaded adsorbent was regenerated and used for five cycles still had appreciable adsorption capacity. The fabricated biosorbent could be a greener sorbent with appreciable adsorption capacity and could be a best alternative to commercial activated carbon, however, further validation against other pollutants would help in strengthening the present study claim.