Biosorption kinetics of cadmium (II) on cross-linked pectin extracted from orange peels at 20°C was studied, obtaining an equilibrium sorption capacity, q , of 99.56 mg/g in pH range e 4.5-5.5. Pectic material was extracted through acid hydrolysis (pH: 1.5, temperature: 90°C, time: 30 min) and crosslinked with formaldehyde acidic solution in order to diminish hydration capacity and swelling, as well as polysaccharide leaching when found in aqueous environment. Biosorption kinetics experimental data showed greater coefficients of correlation (R ) on pseudo second order mathematic model. Physical chemistry parameters: particle size influence (125 µm - 500 µm and 0 µm - 125 µm) and biosorbent and metal concentrations in solution were evaluated in the biosorption kinetics. Pseudo second order -4 -1 -1 constant, k = 8.0x10 g.mg min , of biosorbent with particle size 125-500 µm increase...