This study investigated the adsorption of the heavy metal ions Pb(II), Cu(II), Cd(II), Zn(II), and Ni(II) on a lignin isolated from black liquor, a waste product of the paper industry. Lignin has affinity with metal ions in the following order: Pb(II) > Cu(II) > Cd(II) > Zn(II) > Ni(II). The adsorption kinetic data can be described well with a pseudosecond-order model and the equilibrium data can be fitted well to the Langmuir isotherm. Metal ion adsorption was strongly dependent on pH and ionic strength. Surface complexation modelling was performed to elucidate the adsorption mechanism involved. This shows that lignin surfaces contain two main types of acid sites attributed to carboxylic-and phenolic-type surface groups and the phenolic sites have a higher affinity for metal ions than the carboxylic sites.

Copper-containing mesoporous HMS catalysts prepared via a one-pot synthesis method based on sol−gel chemistry have been systematically characterized focusing on the effect of copper loading. Structural characterization of a series of different copper loading samples was performed by means of N2 adsorption, X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, temperature programmed reduction, N2O titration, and X-ray photoelectron spectroscopy. It is concluded that the copper loading has a great influence on the pore structure of the catalyst. On the basis of the characterizations, the copper species on calcined CuO/HMS samples and reduced Cu/HMS samples were assigned. The synergetic effect between the Cu0 and Cu+ is considered to be responsible for the enhanced catalytic performance in the hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). The maximum ratio of Cu0/Cu+ obtained via tuning the copper loading can result in the highest DMO hydrogenation activity and EG selectivity.

In this study, we investigated the destruction and by-product formation of perfluorooctanoic acid (PFOA) using ultraviolet light and persulfate (UV-PS). Additionally, we developed a first-principles kinetic model to simulate both PFOA destruction and by-product and chlorate (ClO3(-)) formation in ultrapure water (UW), surface water (SW), and wastewater (WW). PFOA degradation was significantly suppressed in the presence of chloride and carbonate species and did not occur until all the chloride was converted to ClO3(-) in UW and for low DOC concentrations in SW. The model was able to simulate the PS decay, pH changes, radical concentrations, and ClO3(-) formation for UW and SW. However, our model was unable to simulate PFOA degradation well in WW, possibly from PS activation by NOM, which in turn produced sulfate radicals.

In order to assess the possibility of using lignin to remove Cr(III) from waters, the adsorption of Cr(III) on lignin isolated from black liquor, a waste product of the paper industry, was investigated. The influences of pH, lignin dosage, contact time, ionic strength, Cr(III) concentration and other metals were investigated. The Cr(III) adsorption was strongly dependent on pH and adsorbent dosage, but independent of ionic strength and other metal ions. The adsorption kinetic data can be described well with pseudo-second-order model and the equilibrium data can be well fitted using Langmuir two-surface model with a maximum adsorption capacity of 17.97 mg/g. Cr(III) adsorption on lignin was mainly through the ion-exchange mechanism and formed inner-sphere complexes with lignin. Successful application in removing Cr(III) was achieved by using a real wastewater sample. This study indicates that lignin has the potential to become an effective and economical adsorbent for the removal of Cr(III) from wastewaters.