Houston et al. 2023 - Alumina nanofibers for Hg(II) and Pb(II) removal

Houston and colleagues synthesized amine-functionalized gamma-alumina nanofibers and tested them as adsorbents for mercury(II) and lead(II) ions in prepared aqueous solutions. This is primary remediation-method evidence, not occurrence evidence for food, ingredients, consumer products, or field drinking-water samples.

Key numbers

Concentration-response and pH

The batch adsorption tests used 20 mg of Al2O3-NH-NH2 nanofiber in 30 mL aqueous solutions at room temperature for 3 hours unless otherwise noted.

The authors compare these test levels with water-contamination context from the literature, but the measured values in this paper are controlled spike-removal experiments.

Kinetics and adsorption capacities

For contact-time experiments, the authors tested 100 mg/L and 250 mg/L Hg(II) and Pb(II) solutions. Most adsorption occurred within the first hour, and no meaningful additional removal occurred between 1 and 3 hours.

Table 2 reports that pseudo-second-order kinetic fits had much higher R2 values than pseudo-first-order fits, which the authors interpret as evidence that chemisorption is the better kinetic description.

Selectivity and desorption

Selectivity experiments mixed 50 mg/L Hg(II) or Pb(II) with separate 100 mg/L or 250 mg/L solutions of Zn(II), Mg(II), Cu(IV), Sn(IV), or Ni(IV), as written by the source. For Hg(II), all 100 mg/L cation-competition solutions retained more than 90% Hg removal: the highest was Hg/Zn at 0.373 mmol/g with 100% Hg adsorbed and 2.87% Zn adsorbed; the lowest was Hg/Ni at 0.343 mmol/g with 93.94% Hg adsorbed and 42.3% Ni adsorbed. At 250 mg/L cation competition, Hg/Ni was highest at 0.367 mmol/g with 98.51% Hg adsorbed, and Hg/Sn was lowest at 0.277 mmol/g with 74.32% Hg adsorbed.

For Pb(II), the nanofiber was less selective. At 100 mg/L cation competition, Pb/Ni was highest at 0.345 mmol/g with 91.5% Pb adsorbed, while Pb/Zn was lowest at 0.118 mmol/g with 50.8% Pb adsorbed. At 250 mg/L cation competition, Pb/Ni was highest at 0.364 mmol/g with 96.54% Pb removal, and Pb/Zn was lowest at 0.245 mmol/g with 56.7% Pb adsorbed.

Desorption with nitric acid increased as acid molarity increased; the source reports 69.5% Hg and 90.2% Pb desorbed at the highest HNO3 condition. For HCl, the optimum desorption was 0.05 M for Hg and 0.5 M for Pb: 62% Hg desorbed at 0.05 M HCl, while Pb desorption was 52% at 0.5 M, 40.3% at 1.0 M, and 38% at 0.05 M. Purified water was the least effective desorption condition, with 2.1% Hg and 3.33% Pb in solution.

Methods (brief)

The authors synthesized amine-functionalized gamma-Al2O3 nanofibers by preparing boehmite from aluminum nitrate and ammonia, calcining at 450 C, and grafting with 3-(2-aminoethylamino) propyl trimethoxysilane under reflux in toluene. The adsorbent was characterized by TEM, SEM-EDS, elemental mapping, XRD, and XPS before and after adsorption.

Adsorption tests used prepared Hg(II) and Pb(II) solutions from mercury chloride and lead salts. Concentration-response experiments covered low to high mg/L concentrations; pH experiments used 50 mg/L Hg(II) and Pb(II) solutions from pH 2 to 10; kinetic experiments used 100 mg/L and 250 mg/L solutions with time points from 10 minutes to 3 hours. Metal concentrations were quantified by ICP-OES. Selectivity tests added competing cations, and desorption tests used demineralized water plus 0.05 M, 0.5 M, and 1.0 M HCl or HNO3.

Implications

Certification: Do not use this source in food, ingredient, drinking-water occurrence, infant-food, supplement, cosmetic, or product benchmark pools. It measures removal from prepared aqueous spike solutions, not contaminant levels in a consumer matrix.

App: Context for water-treatment and remediation notes. The nanofiber showed stronger binding and selectivity for Hg(II) than Pb(II), with rapid one-hour equilibrium under the tested conditions and partial acid desorption.

Courses: Useful for distinguishing sorbent capacity, removal percentage, pH-dependent chemistry, and selectivity from occurrence concentrations. It also illustrates why Hg(II) removal does not substitute for methylmercury evidence.

Wiki pages this source may touch

• remediation-evidence
• mercury
• lead
• index

Verification notes

This page was built from the full PDF, including Table 1 comparator adsorbents, synthesis and adsorption methods, characterization sections, Figure 4 concentration-response discussion, Figure 5 pH response, Figure 6 contact-time results, Table 2 kinetic parameters, Figure 8 selectivity discussion, Figure 9 desorption discussion, conclusion, supplementary-materials note, and data-availability statement. Products and ingredients are intentionally empty because all measured concentrations come from controlled aqueous solutions. The source reports Hg(II) and Pb(II); this page preserves ion-state specificity in prose while using broad Hg and Pb frontmatter metals.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.