Wang et al. 2020 - Lignin-residue biochar for heavy-metal remediation

Wang and colleagues converted lignin-rich residue from a furfural manufacturing process into activated biochars and tested them as aqueous sorbents for Pb(II), Cd(II), and Cu(II). This is primary remediation-method evidence, not food or product occurrence evidence: the measured endpoints are biochar properties, adsorption kinetics, and isotherm capacities rather than concentrations in edible crops, ingredients, consumer products, or drinking water.

Key numbers

Biochar properties

Table 1 reports that both activation routes increased surface area and pore volume relative to hydrochar. Selected source-reported properties:

The acidic-group total above sums the Table 1 carbonyl, carboxylic, lactone, and phenolic groups. The authors attribute the higher adsorption performance of BC-ZnCl2 to its larger surface area, pore volume, and acid-group content.

Adsorption tests and kinetics

Batch adsorption tests used 0.6 g biochar in 100 mL aqueous metal-ion solution at 25 +/- 2 C. Initial concentrations for isotherms ranged from 0.5 to 5.0 mM for Pb(II), Cd(II), and Cu(II). Metal concentrations in filtrates were measured by atomic absorption spectroscopy.

For Pb(II), adsorption was rapid: the paper reports more than 90% of the equilibrium uptake in the first 30 minutes, with equilibrium at about 4 hours. Table 2 gives pseudo-second-order fit values for Pb(II):

Isotherm capacities

Table 3 reports Freundlich and Langmuir fits. The authors state that Langmuir fits were stronger than Freundlich fits overall and that the BC-ZnCl2 material performed better for all three metal ions.

The conclusion also reports BC-ZnCl2 uptake ranges across the tested concentration gradient: Pb(II) 23.1-72.1 mg/g, Cd(II) 6.8-55.6 mg/g, and Cu(II) 8.2-30.5 mg/g. Table 4 compares Pb(II) capacity with other sorbents and lists this study’s Pb(II) adsorption capacities as 42.7 mg/g for BC-H3PO4 and 72.1 mg/g for BC-ZnCl2.

Methods (brief)

Lignin-rich residue from a corn-cob furfural process was dried, milled below 100 mesh, hydrothermally carbonized at 250 C for 2 hours, washed, and then chemically activated. The H3PO4 route mixed hydrochar with 40% H3PO4 at a 1:6 hydrochar/H3PO4 ratio for 24 hours, activated at 500 C for 2 hours under nitrogen, washed to neutral pH, and dried. The ZnCl2 route mixed hydrochar with 40% ZnCl2 at a 1:10 ratio for 24 hours, activated at 500 C, boiled with 1 M HCl, washed until chloride-free, and dried.

Biochars were characterized by nitrogen adsorption/desorption, BET surface area, pore volume, FT-IR, Boehm titration, zeta potential/pHpzc, SEM, TEM, and XRD. Adsorption experiments varied pH, contact time, and initial Pb(II), Cd(II), or Cu(II) concentration; filtrate metal concentrations were analyzed by atomic absorption spectroscopy.

Implications

Certification: Do not use this source in any food, infant-food, supplement, cosmetic, or ingredient occurrence pool. It does not measure consumer-product concentrations or demonstrate a reduction in a food matrix. It is relevant only as remediation context for low-cost carbonaceous sorbents.

App: Context for water-treatment and upstream remediation notes. The key takeaway is that ZnCl2-activated lignin-residue biochar had higher Pb(II), Cd(II), and Cu(II) sorption capacity than H3PO4-activated biochar under controlled aqueous test conditions.

Courses: Useful for teaching the distinction between sorbent capacity and occurrence concentration, plus the role of pH, surface area, acid groups, and Langmuir/PSO model fits in remediation studies.

Wiki pages this source may touch

• remediation-evidence
• agronomic
• lead
• cadmium
• copper
• index

Verification notes

This page was built from the full PDF, including the synthesis methods, adsorption-experiment design, Table 1 biochar properties, Table 2 Pb(II) kinetic fits, Table 3 isotherm fits for Cu(II), Cd(II), and Pb(II), Table 4 Pb(II) comparator capacities, the conclusion, and the supplementary-materials note. The source uses dissolved Pb(II), Cd(II), and Cu(II) nitrate solutions; frontmatter uses the repo’s broader Pb, Cd, and Cu metal slugs while this page preserves ion-state specificity in prose and tables. Products and ingredients are intentionally empty because no food, ingredient, or consumer-product matrix was sampled.

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.