Removal of lead from aqueous solutions and wastewaters using water hyacinth (Eichhornia crassipes) roots

Abstract

Dried ground roots of water hyacinth (Eichhornia crassipes) were used for removal of Pb(II) from aqueous solution. Batch adsorption experiments were conducted with the dried roots (0.1 g dry weight) using 100 mg/L of Pb(II) aqueous solution adjusted at pH 5.0. Equilibrium was obtained in 90 min with a 92% removal of Pb(II). The effect of contact time, pH, adsorbent dosage, initial metal ion concentration on the adsorption of Pb(II) were also studied. Kinetic studies indicated that the adsorption of Pb(II) followed the pseudo-second-order model with a reaction rate constant (k) of 0.0127 mg/(g.min). Kinetics data conforming to the pseudo-second-order model suggest that chemisorption was the rate-limiting step in the adsorption process. The adsorption data were found to fit best into the Langmuir model (R2 = 0.986). The maximum adsorption capacity was found to be ∼50 mg Pb(II) per g of dried roots. To investigate the feasibility of using the water hyacinth roots in a more realistic situation, wastewaters collected from various sources were also tested with the biosorbent. Significant removal of Pb(II) (∼88% to ∼100%) was observed from the wastewaters at pH 5.0. High adsorption capacity, rapid kinetics, and its low cost make water hyacinth dried roots a good candidate for the removal of Pb(II) from wastewaters. Highlights Lead could be removed from wastewaters using non-living water hyacinth roots as biosorbent.; 92% removal of lead from aqueous solution was achieved within 90 min.; Kinetics indicated that the removal process was controlled by chemisorption.; Langmuir model conformed to the isotherm data, suggesting a monolayer adsorption.; The biosorbent removed ∼88% to ∼100% lead from the real wastewaters.;

Keywords

• adsorption
• isotherms
• low-cost biosorbent
• pseudo-second-order kinetic
• wastewater
• water hyacinth roots