ADSORPTION OF Cd (II) IONS FROM AQUEOUS SOLUTIONS ONTO BIOCHAR FROM BIOMASS WASTE

Biochar is a carbonbased material obtained by pyrolysis (in Argon atmosphere) of biomass such as manure produced by cattle farms. The use of biochar in agricultural soils improves the properties of the soil and the yield of agricultural products. Effects of biochar and biocharcompost mixtures on soils favor plant growth and induce an immobilization of heavy metals and organic pollutants. In the present work, the adsorption of Cd(II) ions onto biochar at 25 C in 0.1 M NaClO4 as ionic media has been studied. Preliminary to adsorption study has been the determination of protolysis constants conducted by potentiometric methods by using of glass electrode. The potentiometric data processed by numerical methods1 agree that the surface of solid presents acid sites and basic sites, with the following protolysis constants: >ROH + H+ ⇆ >ROH2+ log KR = 2.6  0.1 >TOH ⇆ >TO + H+ log KT = 8.5  0.1 The adsorption of Cd(II) ions from aqueous solutions has been conducted by isotherm and kinetic studies. The isotherm data collected follow the Langmuir model with a maximum capacity: Γ0 = (95 ± 2) mg/g as well as with an adsorption constant: KL = (0.10 ± 0.06) dm3/mmol. In addiction the adsorption process of the Cd(II) ions reaches equilibrium after about 24 hours (Figure 1). The kinetic data are compatible with a pseudosecond order model, where the intraparticle diffusion represents the slow stage of the process. The measurements carried out in aqueous solutions show that the use of biochar prepared from solid livestock waste allows to obtain a removal by adsorption of 50% of the Cd (II) ions at pH = 5.5 (Figure 2).