Chen, M., Li, L., Grace, J., Tazaki, K., Shiraki, K., Asada, R., et al. (2007). Remediation of acid rock drainage by regenerable natural clinoptilolite. Water, Air, Soil Pollut., 180(1-4), 11–27.
Abstract: Clinoptilolite is investigated as a possible regenerable sorbent for acid rock drainage based on its adsorption capacity for Zn, adsorption kinetics, effect of pH, and regeneration performance. Adsorption of Zn ions depends on the initial concentration and pH. Adsorption/Desorption of Zn reached 75% of capacity after 1-2 h. Desorption depended on pH, with an optimum range of 2.5 to 4.0. The rank of desorption effectiveness was EDTAEDTA > NaCl > NaNO3 > NaOAc > NaHCO3 > Na2CO3 > NaOH > CeCa(OH)(2). For cyclic absorption/desorption, adsorption remained satisfactory for six to nine regenerations with EDTA and NaCl, respectively. The crystallinity and morphology of clinoptilolite remained intact following 10 regeneration cycles. Clinoptilolite appears to be promising for ARD leachate treatment, with significant potential advantages relative to current treatment systems.
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Murray-Gulde, C. L. (). Contributions of Schoenoplectus californicus in a constructed wetland system receiving copper contaminated wastewater. Water, Air, Soil Pollut., 163(1-4), 355–378.
Abstract: Functional roles of Schoenoplectus californicus, giant bulrush, were evaluated in an 3.2 ha (8-acre) constructed wetland treatment system receiving copper-contaminated water. The constructed wetland used in this research was designed to decrease bioavailable copper concentrations in a wastestream and eliminate associated toxicity to downstream biota by exploiting the thermodynamic processes responsible for copper speciation. This was achieved by integrating carbon, sulfur and copper biogeochemical cycles. In this system, S. californicus, which represents an integral part of the carbon cycle, provides a physical, chemical and biological role in removing metals from the aqueous phase. The specific contributions of S. californicus in this system are to provide a sustainable carbon source for removal of copper by (1) provision of an organic ligand for sorption of copper entering the system, (2) production of organic ligands through growth of S. californicus, (3) accretion of organic ligands over time due to decomposition of S. californicus detritus, and (4) use of organic carbon as an energy source for dissimilatory sulfate production. Shoots and roots of viable S. californicus sorbed 0.88% and 5.88%, respectively, of copper entering the system. The half-life of S. californicus detritus in the constructed wetland system was approximately 184 d, indicating that sufficient detritus will accrete over time, providing binding sites for copper and an energy source for bacterial metabolic processes that contribute to copper immobilization in wetland systems.
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