Pan et al. 2021 - lignosulfonate/chitosan Pb(II) adsorbent

Pan and colleagues synthesized a sodium lignosulfonate/chitosan adsorbent and tested its removal of Pb(II) from prepared aqueous lead nitrate solutions. This is primary water-treatment and adsorbent-performance evidence, not food, ingredient, or consumer-product occurrence evidence.

Key numbers

Orthogonal synthesis screen

Table 2 reports nine adsorbent formulations and Pb(II) adsorption capacity:

The factor influence decreased in the order potassium persulfate > chitosan > sodium lignosulfonate > NMBA. The authors selected 0.3 g sodium lignosulfonate, 0.3 g chitosan, 0.07 g potassium persulfate, and 0.0115 g NMBA as the best synthesis levels. Under the cited adsorption test conditions, the optimized material reached 345 mg/g Pb(II) adsorption capacity.

Adsorption test conditions

All adsorption experiments used 50 mL prepared Pb(II) solution. The kinetic test used 100 mg/L initial Pb(II), 0.01 g adsorbent, pH 7.0, 20 degrees C, and 5-240 min contact time. The isotherm test used 100-900 mg/L initial Pb(II), 0.01 g adsorbent, pH 7.0, and 20 degrees C. The thermodynamic test used 100 mg/L initial Pb(II), 0.01 g adsorbent, pH 7.0, and 20-60 degrees C. The pH experiment varied pH from 1.0 to 7.0 at 100 mg/L Pb(II), 0.01 g adsorbent, and 20 degrees C. The adsorbent-dose experiment varied LS/CS dose from 0.01 to 0.07 g at 100 mg/L Pb(II), pH 7.0, and 20 degrees C.

The authors state that adsorption performance was pH-sensitive. The zeta-potential zero point was pH 4.1; above roughly pH 4, the adsorbent surface was negatively charged and Pb(II) attraction increased. The conclusion reports 345 mg/g capacity at 100 mg/L Pb(II), pH 7.0, 0.01 g adsorbent, and 120 min reaction time.

Kinetic, isotherm, and thermodynamic fits

Table 3 reports kinetic fitting:

The authors interpret the better pseudo-second-order fit as evidence that the Pb(II) adsorption process is a multi-process adsorption with chemical adsorption behavior.

Table 4 reports isotherm fitting:

The Langmuir model fit better than Freundlich, and the authors infer monolayer-like adsorption.

Table 5 reports thermodynamic parameters for Pb(II):

The authors interpret negative Delta G0 and positive Delta H0 as spontaneous, endothermic adsorption that becomes more favorable as temperature rises.

Mechanism characterization

SEM showed a porous LS/CS surface before adsorption and a sheet-like surface after adsorption. EDS detected Pb on the post-adsorption surface. FT-IR peak shifts after Pb(II) adsorption involved O-H, N-H, C-O-C, C=C, and sulfonic-related features. The proposed mechanism combines electrostatic attraction with Pb-pi, Pb-O, and Pb-N interactions.

Methods (brief)

The authors synthesized LS/CS adsorbent by neutralizing acrylic acid, then adding sodium lignosulfonate, chitosan, potassium persulfate, NMBA, and water before sonication at 70 degrees C for 1 h. Products were washed with ethanol, dried, and ground. Orthogonal design software selected the nine formulation runs.

Characterization used FT-IR, SEM/EDS, thermogravimetric analysis, and zeta-potential measurement. Residual Pb(II) in solution before and after adsorption was measured by flame atomic absorption spectrophotometry at 283.3 nm. Adsorption capacity was calculated from initial concentration, equilibrium concentration, solution volume, and adsorbent mass.

Implications

Certification: Do not use this source in HMTc food, ingredient, or consumer-product occurrence pools. It uses prepared aqueous Pb(II) solutions to evaluate adsorbent performance.

App: Useful as water-treatment context for Pb(II) removal mechanisms, especially lignosulfonate/chitosan materials, pH-dependent adsorption, and Langmuir/pseudo-second-order fit behavior.

Courses: Useful for teaching the difference between occurrence concentration in a consumed matrix and controlled-remediation capacity in a prepared aqueous test system.

Wiki pages this source may touch

• lead
• wastewater-irrigation
• index

Verification notes

This page was built from the full PDF, including the abstract, materials and methods, orthogonal design, Tables 1-5, Figures 1-8, conclusions, supplementary-materials note, and data-availability statement. The paper reports primary Pb(II) adsorption and residual-solution measurement data, but no food, ingredient, consumer-product, or market-sampling concentrations. Reagent and instrument brand names were omitted from this page under the brand firewall.

Page history

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