Removal of Pb(II) by lignin-sodium alginate composite in a fixed-bed column

ABSTRACT

A kind of adsorbent (Hydrogel-I) derived from sodium alginate and modified alkaline lignin (MAL) has been proved to possess a good adsorption performance for Pb(II)-loaded wastewater based on batch experiments. However, practical removal of Pb(II)-loaded-wastewater is a continuous and dynamic process. Herein, Hydrogel-I was further evaluated by packing it into a fixed-bed column. The breakthrough curves were established under different inflow rates (0.159–0.318 L/min), inflow directions (down-inflow mode and top-inflow mode), initial concentrations (5–20 mg/L) of Pb(II), and bed depths (20–60 cm). The results indicated that the slower inflow rate (0.159 L/min), down-inflow mode, lower initial concentration (5 mg/L), and higher bed depth (60 cm) prolonged breakthrough times (t_b) and saturation times (t_s). Compared to the top-inflow mode, the down-inflow mode guaranteed enough contact between Hydrogel-I and Pb(II). The values of adsorption capacity at t_b, t_s, and the removal efficiency under the down-inflow mode were higher than that under top-inflow mode by 2.33, 0.78, and 0.07 times, respectively. Hydrogel-I beads exhibited better adsorption performance than other adsorbents by comparing the rate constant (k_AB) and the adsorption capacity (N₀). The k_AB and N₀ of Hydrogel-I beads were calculated to be 0.0034 L/(mg·min⁻¹) and 678 mg/L. Hydrogel-I beads showed good regeneration ability in a three-adsorption-desorption cycle. Meanwhile, FT-IR analysis showed that the groups of –NH/–NH₂, C=S, and C–S were proved to be the adsorption sites. This study could prove valuable insight into the practical application of Hydrogel-I for dynamic removal of Pb(II) in an inflow-through column.

GRAPHICAL ABSTRACT

KEYWORDS:

• Fixed-bed column
• Pb(II)
• Breakthrough curves
• Adsorption
• Regeneration

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data used to support the findings of this study are available from the corresponding author upon request.

Additional information

Funding

This work was funded by the Key R&D Program of Shaanxi Province (2019SF-253), the Natural Science Foundation of China (21922606), the Fundamental Research Funds for the Central Universities (CHD 300102291504), and the Key Laboratory of Resource Chemistry Ministry of Education (KLRC_ME2102). We would also thank very much to the editor and anonymous reviewers for their valuable opinions.