Recycling of Waste Toner Powder as Adsorbent to Remove Aqueous Heavy Metals.

The removal of Cd2+, Zn2+ and Ni2+ from metal solutions onto waste toner power (WTP) was investigated. The influence of parameters such as pH, contact time, initial metal concentration and adsorbent dosage was studied in batch adsorption experiments. Batch equilibrium experiments showed that the highest removal efficiency for Zn2+ and Cd2+ occurs at pH 7, while pH 5 is the most suitable for Ni2+ removal. The amount of metal removed (mg/g) improved when increasing the initial concentration, and sorption of heavy metals reached equilibrium in 24 h. Metals' uptake increased with increasing adsorbent dosage. The adsorption isotherms of Zn2+, Cd2+ and Ni2+ onto WTP fit the Langmuir better than the Freundlich model with correlation coefficient R2 values ranging from 0.998 to 0.968 and 0.989 to 0.881, respectively. The data showed that the maximum adsorption capacity of heavy metals, amax, ranged from 2.42 to 1.61 mg/g, from 6.22 to 2.01 mg/g and from 3.49 to 2.56 mg/g for Ni2+, Zn2+ and Cd2+, respectively, with the three WTPs used in this study. This adsorbent can potentially be used to remove metal ions from wastewater.

A multi-faceted, environmental forensic characterization of a paradigmatic brownfield polluted by hazardous waste containing Hg, As, PAHs and dioxins.

Hg and As mining-metallurgy plants have severely impacted environmental compartments. La Soterraña site (northern Spain) has been previously studied in this context. However, here we used a novel multi-purpose forensic approach to examine accumulations not only of mining-metallurgical waste (volumes above 80,000 t) but also C&D waste as a repository of pollutants (above 10% of As leached in standard tests) at this site. High Hg and As content in very fine grain-size fractions (up to 100,000 mg/kg of As in metallurgy waste below 10 µm) was significant, as was the predominance of As (III) in metallurgy waste. In addition, GC-MS techniques revealed the predominance of PAHs (secondarily Oxy-PAHs and PCBs), which showed a pyrogenic fingerprint, as determined by molecular ratios. Moreover, toxic organometallics (Hg-aromatics) were detected and metallurgy waste was identified as a source of dioxins and furanes (TEQ close to 30). On the basis of our observations, La Soterraña emerges as one of the most polluted sites in Europe and therefore requires urgent remediation. Our key findings indicate that C&D waste should be considered hazardous. Metallurgy waste, in turn, raises maximum concern given the simultaneous presence of toxic inorganic and organic contaminants.