Studies on the uptake of lead and zinc by lignin obtained from black liquor – a paper industry waste material

Adsorption of metal ions on lignin

“…Similar to the adsorption kinetics, the maximum equilibrium adsorption capacity (q m ) was obtained for Pb(II) (0.432 mmol/g), which decreased to 0.360 mmol/g for Cu(II), 0.226 mmol/g for Cd(II), 0.172 mmol/g for Zn(II), and 0.102 mmol/g for Ni(II). The lignin in the present study showed higher adsorption capacities for the metal ions compared with the adsorption capacities of other lignin adsorbents published in the review paper [31] with the exception of the exceptionally high adsorption capacities reported by Srivastava et al and Mohan et al [16,20]. Tables 3 and 4.…”

“…The average pore diameter was 147.6Á and the specific surface area of lignin was 21.7 m 2 /g as measured by the N 2 -BET method. The surface area was not as high as we expected [16,20,24], probably due to the BET measurement method we used which has been demonstrated not to quantitively detect the inner surface area of some sorbents, resulting in lower specific surface area values [37]. The difference in physical and chemical properties of lignin from different origins and the extraction or isolation technology used may also have contributed to the lower specific surface areas to some extent.…”

“…Intensive studies have therefore been carried out to develop more effective and inexpensive metal adsorbents. Candidate materials include industrial or agricultural waste products such as waste slurry [7,8], fly ash [9,10], lignite [11,12] pine bark [13], peat [14,15], and lignin [16][17][18][19][20][21][22][23][24][25]. Babel and Kurniawan [26] and Bailey et al [27] have reviewed the application of low-cost adsorbents for heavy metal removal from contaminated waters.…”

“…Suhas et al [31] have reviewed the literature on lignin as a biosorbent. Srivastava et al [16] obtained remarkably high uptake of Pb(II) and Zn(II), up to 1587 and 73 mg/g for Pb(II) and Zn(II), respectively, by using lignin extracted from black liquor. Demirbas [24] reported a maximum adsorption capacity of 8.2-9.0 mg/g for Pb(II) and 6.7-7.5 mg/g for Cd(II) on lignin from beech and poplar wood modified by alkaline glycerol delignification.…”

“…Some studies have found that ion-exchange mechanisms may be responsible for the sorption of metal ions on lignin [17,[21][22][23]. Srivastava et al [16] and Mohan et al [20] suggested that no single mechanism could explain the pro-cess of metal removal by lignin. Several processes including ion exchange, surface adsorption, and complexation, have been suggested to explain the mechanisms involved.…”