[Sorption characteristics of tea waste modified by hydrated ferric oxide toward Pb(II) in water].

Hydrated ferric oxide was successfully impregnated onto tea waste by precipitation to obtain a new sorbent named HFO-TW, the adsorption characteristics of which toward Pb(II) in aqueous solution was investigated by evaluating the effects of pH value, contact time, coexisting ion, temperature, and initial concentration of Pb(II). The Pb(II) sorption onto HFO-TW was pH- dependent, and the higher pH value was more helpful for Pb(II) adsorption onto HFO-TW in the pH range of 2.5-7. Lead sorption speed was quick and could reach equilibrium within 100 min, and the kinetics curve could be fitted well by both pseudo-first and pseudo-second models. The related coefficient was 98.8%. HFO-TW exhibited highly selective lead retention and the adsorption capacity of Pb(II) onto HFO-TW was declined by only 12.1 mg · g(-1) and 8.1 mg · g(-1) in the presence of competing Ca(II), Mg(II) at 50 times of the target ion. In addition, Pb(II) sorption onto HFO-TW could be described satisfactorily by Langmuir model, and the maximal sorption capacity calculated by Langmuir equation was 89.43 mg · g(-1), which was much higher than the unmodified tea waste and other bio-sorbents. All the results validated that HFO-TW was a promising sorbent for removal of lead from waters.