Mehanathan et al. 2023 - Magnesium oxide nanoparticles for As(V) remediation

Mehanathan and colleagues tested commercial magnesium oxide nanoparticles calcined at 650 C for adsorption of pentavalent arsenic, reported as arsenate/As(V), from aqueous solution. This is primary remediation-method evidence, not food, ingredient, product, or drinking-water occurrence evidence: the measured endpoints are adsorbent structure, adsorption kinetics, isotherm capacity, pH response, dosage response, and regeneration.

Key numbers

Calcination and adsorbent properties

Magnesium oxide nanoparticles were calcined at 650 C for 1 hour. Table 2 reports that calcination increased pore-size distribution while reducing BET surface area and single-point pore volume:

XRD showed both uncalcined and calcined samples as periclase magnesium oxide, with average particle size increasing from 28.40 nm to 34.68 nm after calcination. The authors report a point of zero charge of 8.7 for the calcined particles.

Kinetics

Kinetic tests used 0.05 g calcined MgO in 100 mL arsenate solution at 10, 20, and 50 mg/L, pH 7.0 +/- 0.1, 200 rpm, and 25 +/- 2 C for 7 hours. Arsenic was measured by AAS.

Table 4 reports these kinetic parameters:

The authors interpret the non-linear pseudo-first-order model as the better fit and note rapid adsorption in the first 75 minutes, with equilibrium after about 195 minutes.

Isotherm, pH, dosage, and regeneration

Table 1 compares this study with other magnesium-associated arsenate adsorbents and gives an experimental maximum adsorption capacity of 115.27 mg/g and modeled Qmax of 131.93 mg/g under pH 7, 50 mg/L As(V), 7 hour contact time, and 0.5 g/L adsorbent dosage.

Table 6 reports:

The authors identify the Freundlich model as the best isotherm fit, indicating heterogeneous, multilayer adsorption. Table 7 reports favorable Langmuir separation factors (RL) from 0.135 at 1 mg/L to 0.003 at 50 mg/L.

The pH study used 10 mg/L arsenate, 0.5 g/L calcined MgO, and 7 hours contact time. The highest adsorption capacity was at pH 10. Increasing adsorbent dosage above 0.5 g/L reduced the reported capacity, so the authors recommend 0.5 g/L as the favorable batch dosage. Regeneration with 1 M NaOH gave 64.01% regeneration efficiency in the second cycle, with performance declining as cycles increased.

Methods (brief)

Commercial magnesium oxide nanoparticles were calcined at 650 C for 1 hour at 5 C/min. Morphology and elements were characterized by SEM/EDX; surface area and pore volume by nitrogen adsorption-desorption/BET; crystal structure by XRD; functional groups by FTIR; and surface charge/PZC by zeta potential. Arsenate stock solution was prepared from sodium arsenate dibasic heptahydrate and diluted for tests. Total arsenic in filtrates was measured by atomic absorption spectroscopy using an external electrode discharge lamp and daily calibration curves.

Batch studies covered kinetics, isotherms, pH effect, adsorbent dosage, and regeneration. Arsenate results are controlled aqueous-spiking experiments, not field water occurrence data.

Implications

Certification: Do not use this source in product, ingredient, drinking-water, or food-occurrence pools. It is a remediation-method study using prepared arsenate solutions.

App: Context for water-treatment and remediation notes. Calcined MgO at 650 C showed high As(V) adsorption capacity at low adsorbent dosage, but regeneration declined after repeated cycles and the study did not test real contaminated water matrices.

Courses: Useful for teaching arsenate speciation, pH/PZC effects, Freundlich versus Langmuir model selection, and why adsorption capacity cannot be treated as an occurrence concentration.

Wiki pages this source may touch

• remediation-evidence
• arsenic-inorganic
• index

Verification notes

This page was built from the full PDF, including Table 1 comparator capacities, Table 2 BET properties, XRD/FTIR/zeta discussion, batch adsorption methods, Table 4 kinetic parameters, Table 5 Weber-Morris/Elovich parameters, Table 6 isotherm fits, Table 7 separation factors, pH and dosage figures, regeneration discussion, and the conclusion. The source tests As(V)/arsenate only; frontmatter uses the repo’s broader inorganic-arsenic slug while this page preserves the pentavalent arsenic species in prose. Products and ingredients are intentionally empty because no food, ingredient, drinking-water field sample, 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.