TY - JOUR
T1 - Anaerobic precipitation of manganese and co-existing metals in mine impacted water treated with crab shell-associated minerals
AU - Robinson-Lora, Mary Ann
AU - Brennan, Rachel A.
N1 - Funding Information:
This material is based upon work supported by the National Science Foundation, CAREER Award No. CBET-0644983. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. Three anonymous reviewers are thanked for their helpful comments to improve the manuscript.
PY - 2011/5
Y1 - 2011/5
N2 - The chemical and physical treatment mechanisms by which crab shell removes metals from mine impacted water (MIW) were evaluated under anaerobic and biologically limited conditions in closed systems and kinetic tests. Raw (R-SC20) and deproteinized (DP-SC20) crab shell were tested and compared to limestone to quantify the contribution of chitin-associated minerals and proteins to alkalinity generation and metal precipitation. Single-metal closed systems (initial Mn and Fe=0.18mM and Al=0.34mM) containing 5g/L of either R- or DP-SC20, yielded an increase in pH from 3 to 9.2-10.2, generation of 0.83-1.87mM of alkalinity, and resulted in ≥95% removal of metals within 72h. In contrast, 5-125glimestone/L only raised the pH to 7.8-8.3, produced lower alkalinity (0.56-0.63mM), and resulted in less metal removal (≤85%). In kinetic tests with 5g-DP-SC20/L, removal of ≥95% of the initial metal load was achieved after 0.5, 6, and 48h for Al, Fe, and Mn, respectively. Geochemical calculations (PHREEQC) indicate that limestone-treated systems were close to equilibrium with calcite (CaCO3), whereas octacalcium phosphate (Ca4H(PO4)3) appears to be a controlling phase in systems treated with R- and DP-SC20. The probable mechanisms for Mn removal are the precipitation of rhodochrosite (MnCO3) and/or sorption. In the case of Al and Fe, geochemical calculations point to the precipitation of hydroxides; however, visual observations in Fe systems suggest the formation of green rust, a precursor of other, more stable phases like goethite or lepidocrocite. Several factors may account for the faster changes observed with R- and DP-SC20 compared to limestone: increased dissolution and degree of supersaturation, the presence of phosphates, the release of organic compounds, and a significantly larger surface area. These results are the first to verify and quantify the capacity of crab shell-associated minerals to treat MIW under biologically limited conditions.
AB - The chemical and physical treatment mechanisms by which crab shell removes metals from mine impacted water (MIW) were evaluated under anaerobic and biologically limited conditions in closed systems and kinetic tests. Raw (R-SC20) and deproteinized (DP-SC20) crab shell were tested and compared to limestone to quantify the contribution of chitin-associated minerals and proteins to alkalinity generation and metal precipitation. Single-metal closed systems (initial Mn and Fe=0.18mM and Al=0.34mM) containing 5g/L of either R- or DP-SC20, yielded an increase in pH from 3 to 9.2-10.2, generation of 0.83-1.87mM of alkalinity, and resulted in ≥95% removal of metals within 72h. In contrast, 5-125glimestone/L only raised the pH to 7.8-8.3, produced lower alkalinity (0.56-0.63mM), and resulted in less metal removal (≤85%). In kinetic tests with 5g-DP-SC20/L, removal of ≥95% of the initial metal load was achieved after 0.5, 6, and 48h for Al, Fe, and Mn, respectively. Geochemical calculations (PHREEQC) indicate that limestone-treated systems were close to equilibrium with calcite (CaCO3), whereas octacalcium phosphate (Ca4H(PO4)3) appears to be a controlling phase in systems treated with R- and DP-SC20. The probable mechanisms for Mn removal are the precipitation of rhodochrosite (MnCO3) and/or sorption. In the case of Al and Fe, geochemical calculations point to the precipitation of hydroxides; however, visual observations in Fe systems suggest the formation of green rust, a precursor of other, more stable phases like goethite or lepidocrocite. Several factors may account for the faster changes observed with R- and DP-SC20 compared to limestone: increased dissolution and degree of supersaturation, the presence of phosphates, the release of organic compounds, and a significantly larger surface area. These results are the first to verify and quantify the capacity of crab shell-associated minerals to treat MIW under biologically limited conditions.
UR - http://www.scopus.com/inward/record.url?scp=79953725109&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=79953725109&partnerID=8YFLogxK
U2 - 10.1016/j.apgeochem.2011.02.006
DO - 10.1016/j.apgeochem.2011.02.006
M3 - Article
AN - SCOPUS:79953725109
SN - 0883-2927
VL - 26
SP - 853
EP - 862
JO - Applied Geochemistry
JF - Applied Geochemistry
IS - 5
ER -