Modification of porous starch for the adsorption of heavy metal ions from aqueous solution

• Xanthate and carboxylate groups were attached to the walls of porous starch.
• Concentration effect on the adsorption capacity of Pb2+ was investigated.
• Adsorption behavior of Pb2+ on modified porous starches fit the kinetic models.
• Maximum adsorption capacities were 109.1 and 57.6 mg/g for these modified starches.

Porous starch xanthate (PSX) and porous starch citrate (PSC) were prepared in anticipation of the attached xanthate and carboxylate groups respectively forming chelation and electrostatic interactions with heavy metal ions in the subsequent adsorption process. The lead(II) ion was selected as the model metal and its adsorption by PSX and PSC was characterized. The adsorption capacity was highly dependent on the carbon disulfide/starch and citric acid/starch mole ratios used during preparation. The adsorption behaviors of lead(II) ion on PSXs and PSCs fit both the pseudo-second-order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity from the Langmuir isotherm equation reached 109.1 and 57.6 mg/g for PSX and PSC when preparation conditions were optimized, and the adsorption times were just 20 and 60 min, respectively. PSX and PSC may be used as effective adsorbents for removal of heavy metals from contaminated liquid.