Fabrication of thiosemicarbazide-modified biochar/carrageenan composite beads based on Eichhornia crassipes for effective removal of Pb (II) from aqueous medium

Abstract

Several biomasses have been applied as environmentally friendly substitutes to produce biochar, which can be utilized to remediate effluents that contain inorganic chemicals. This study applied water hyacinth (Eichhornia crassipes) as a foundation source for the assembly of thiosemicarbazide-modified biochar (BC), which then was modified with potassium carrageenan (KC). Thiosemicarbazide-modified biochar (BC), potassium carrageenan (KC), and thiosemicarbazide-modified biochar/carrageenan composite beads (BKC) were described by several physicochemical methods. The adsorption of Pb (II) onto the three solid adsorbents was investigated under various experimental conditions. The BKC composite beads revealed a surface area of 687.43 m2/g and a mesoporous structure. The best adsorption conditions were found to be 25 min as an equilibrium time, 1.2 g/L of adsorbent dose, and a solution pH of 5 at a temperature of 15 °C. The pseudo-second-order, Elovich kinetic models, Langmuir, and Temkin isotherms were well familiar to the experimental data, inferring that the progression was physical monolayer adsorption onto the homogenous surface. The highest capacity of Pb (II) adsorption onto BKC was 460.45 mg/g at 15 °C. Thermodynamic measurements proved that adsorption was a spontaneous process and endothermic in the case of BC and BKC while exothermic for KC. Furthermore, BKC showed high reusability conditions.