Assessing the plant phytoremediation efficacy for azolla filiculoides in the treatment of textile effluent and redemption of Congo red dye onto azolla biomass

Abstract

In this work, Azolla filiculoides was used for the bioremediation of a textile effluent and as a potential sorbent for the rejection of Congo red (CR9) dye from a synthetic aqueous solution. The sorbent was characterized, and a pot culture test was carried out to assess the physiological responses in a controlled environment. The response of the plants to the exposure to the emanating pollutants was subordinate. The BOD, COD, and TDS removals were found to be 98.2%, 98.23%, and 90.29%, respectively. Moreover, the dried biomass was studied for the expulsion of CR9, and the process variables were optimized. The maximum CR9 removal was 95% at the optimal conditions of 2 g/L of the sorbent dose at acidic pH. Equilibrium data for adsorption were analyzed using a two-parameter isotherm model. It was observed that the Langmuir isotherm fit with the data (R2 = 0.98) and also had satisfactory lower error values, with its maximum sorption capacity reaching 243 mg/g. The pseudo-second-order kinetics were well fitted (R2 = 0.98). The mass transfer models and the thermodynamic parameters of the system were evaluated. The regeneration studies also showed that the uptake efficacy in the fifth cycle is reduced by 20% when compared with the first cycle. The results show that the biomass was a capable sorbent for the removal of CR9.