Brad J. Busche

Removal of Heavy Metals from Aqueous Solution Using Novel Nanoengineered Sorbents: Self-Assembled Carbamoylphosphonic Acids on Mesoporous Silica

Self‐assembled monolayers of carbamoylphosphonic acids (acetamide phosphonic acid and propionamide phosphonic acid) on mesoporous silica supports were studied as potential absorbents for heavy and transition metal ions in aqueous wastes. The adsorption capacity, selectivity, and kinetics of the materials in sequestering metal ions, including Cd2 +, Co2 +, Cu2 +, Cr3 +, Pb2 +, Ni2 +, Zn2 +, and Mn2 +, were measured in batch experiments with excess sodium ion. The solution pH ranged from 2.2 to 5.5. The kinetics study shows that the adsorption reached equilibrium in seconds, indicating that there is little resistance to mass transfer, intraparticle diffusion, and surface chemical reaction. The competitive adsorption study found the phosphonic acid‐SAMMS to have an affinity for divalent metal ions in decreasing order of Pb2 + > Cu2 + > Mn2 + > Cd2 + > Zn2 + > Co2 + > Ni2 +. The measured Cd2 +adsorption isotherm was of the Langmuirian type and had a saturation binding capacity of 0.32 mmol/g.

Electrophilic Aromatic Substitutions of Amine and Sulfonate onto Fine-Grained Activated Carbon for Aqueous-Phase Metal Ion Removal

ABSTRACT Two new materials for adsorption of metal ions from aqueous media have been developed. The organic functional groups amine (−NH2) and sulfonate (−SO3H) were successfully attached to a commercially available fine-grained activated carbon (AC) via electrophilic aromatic substitutions. The surface properties of the materials were investigated using FTIR spectroscopy, XPS, BET surface area analysis, gravimetric methods, and elemental analysis. The NH2-AC and SO3H-AC each had a functional group density of 3 mmol/g. Batch metal ion adsorption experiments were conducted to determine metal binding properties of the adsorbent materials. Based on the distribution coefficients (Kd) of metal ions tested, the unmodified AC and sulfonated-AC both had an affinity for metal ions in decreasing order of Nd > Lu ≈ La > Pb > Cu > Ni ≈ Cd > Mn ≈ Ca, while the amine-AC had an affinity for metal ions in the order of Cu ≫ Nd ≈ Lu ≈ La > Pb > Ni > Cd > Mn ≈ Ca. With maximum Kd values of 130,000 for amine-AC and 25,000 for sulfonated-AC, compared to a Kd of 2,000 for unmodified AC, the modified activated carbons have a strong potential for use in removing heavy metal ions and lanthanide ions from aqueous wastes.

Synthesis of carbamoylphosphonate silanes for the selective sequestration of actinides

The synthesis of carbamoylphosphonate silanes (CMPO analogs) designed for sequestering actinide cations in self-assembled monolayers on mesoporous supports (SAMMS) is described.