Abstract
The response surface methodology has been extended to study the adsorption of malachite green dye (MG) on Indian Neem leaf powder (NLP), Azadirachta indica. The study was experimented by varying the solution concentration from 10 to 100 mg/l. The removal percentage of MG was determined by spectrophotometer at wavelength of 618 nm. Design Expert 11.0 was used as a tool to study the optimal conditions of MG adsorption (applying 2-factorial interaction model of central composite design) and evaluation of interaction effects of different operating parameters including pH, time, solute concentration, temperature and adsorbent dosage. Numerical optimization helped to identify the optimal conditions for achieving the targeted dye removal of 95.493% when the pH, time, solute concentration, temperature and adsorbent amount were set at the range of 6.868, 36.4 min, 27.899 mg/l, 308.477 K, and 4.3475 g/l respectively. The experimental results indicate that the maximum adsorption capacity of NLP depends on various operating parameter like, pH, dye concentration, particle size of adsorbents and it’s activation. It was noted that adsorption capacity of the NLP increases from 33.33 to 66.72 mg/g when it was activated with dilute HCl. The higher correlation coefficient value (R2) of Langmuir isotherm 0.996 and lower p value (0.01203) indicate the fitness of the response surface 2FI model developed. Kinetic studies displayed the suitability of pseudo second order reaction for this adsorption process. The thermodynamic study show that the sorption process is exothermic and spontaneous in nature. It was observed that the adsorbent NLP in the form of fine powder are very effective for the removal of MG from its aqueous solution. The satisfactory values of regression coefficients at different temperature, and fittings of adsorption isotherms indicate that Indian NLP is a promising adsorbent for treatment of textile dyes.
Highlights
The Neem tree (Azadirachta indica) of family Meliacae is native to the Indian sub-continent and it has been in use since ancient periods to treat various human disorders and other hygienic activities (Bhattacharyya and Sharma 2003)
The numerical optimization of the present study indicate that the optimum values of the different independent variables such as pH: 6.868, time: 36.40 min, temperature: 308.477 K, solute concentration:, 27.899 mg/l, and adsorbent amount: 4.3475 g/l in order to achieve the targeted malachite green removal of 95.493% which is very close to the experimental value of dye removal: 94.3004%
Present study confirmed the potential capability of Indian Neem leaf powder (A. indica) as natural bio-adsorbent to remove malachite green dye (MG) dye from aqueous synthetic solution or industrial wastes
Summary
The Neem tree (Azadirachta indica) of family Meliacae is native to the Indian sub-continent and it has been in use (especially its leaves and barks) since ancient periods to treat various human disorders and other hygienic activities (Bhattacharyya and Sharma 2003). The effluents of dyeing industries use highly colored compounds having high chemical and biological oxygen demand (Garg et al 2004). These dye containing effluents can harm the living systems of the natural water bodies as well as the human beings due to their carcinogenic, allergenic and toxic effect (Akar et al 2009; Chakraborty et al 2020). Effective utilization of NLP as an alternative adsorbent for the treatment of textile dying wastes and the investigation of its adsorption characteristics is a big challenge to the researchers till
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