AGRICULTURAL BY-PRODUCTS AS ADSORBENTS FOR ENVIRONMENTAL REMEDIATION
Location: Commodity Utilization Research
Title: REMOVAL OF HEAVY METALS FROM SOLUTION BY A NOVEL SWINE MANURE-BASED ACTIVATED CARBON
Submitted to: Poultry Waste Management Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 1, 2007
Publication Date: October 1, 2007
Citation: Lima, I.M., Marshall, W.E. 2007. Removal of heavy metals from solution by a novel swine manure-based activated carbon. In: Proceedings of Sardina 2007, Eleventh International Waste Management and Landfill Symposium, CISA, Environmental Sanitary Engineering Centre, Italy (Published on CD).
The impact of excessive animal manure production on the quality of life and the environment is generating public and regulatory concern. Additionally, water quality issues and the dwindling availability of potable water have become a hot topic worldwide. Viable value-added alternatives that involve the reuse, rather than disposal of animal manures, are therefore in need. A team of scientists with ARS, USDA, Southern Regional Research Center, in New Orleans, Louisiana has been involved in converting animal manures into valuable adsorbents. In this particular study, swine manure was used as the precursor. The process involved pyrolyzing and steam-activating pelletized forms of swine manure at various activation times (from 15 to 60 min) and water flow rates (1, 3 and 5 ml/min) to produce granular activated carbons, GACs that were used to adsorb unwanted pollutants from aqueous environments. Specifically, in this study, the adsorption behavior towards four different metals (Cu2+, Cd2+, Ni2+ and Zn2+) was measured for the steam activated swine manure-based carbons, at 5 mM concentrations. Essays were set for both individual and competitive adsorption. Physico-chemical properties of the swine manure-based carbons, such as yield, surface area, ash content, and attrition were also measured. All properties measure for swine manure-based carbons were compared with those obtained for carbons made from three traditional precursors, coal, coconut and wood. Carbon yields (dry basis) decreased with both activation time and flow rate and for the swine manure-based carbons they ranged between 12.5% and 20.2% for 60 min activation at 5 ml/min and 15 min activation at 3 ml/min, respectively. The activation strategy had an influence on the carbon’s ability to adsorb the metals, both individually and in competition mode. Activated carbons were most effective at adsorbing copper ions and zinc ions with adsorption values ranging respectively between 66.8 % to 91.8% and 39.7 to 77.0% of total metal available, depending on the activation strategy. These values were significantly larger than the ones found for the reference carbons made from coal, coconut shells and wood, with adsorption values of 0%, 24.9% and 23.0% for copper ion and 7.3%, 6.0% and 14.8% for zinc ion, respectively. In a competition mode adsorption values were lower but swine manure-based carbons excelled over the reference carbons. Experiments showed that the highest removal rate in a competition situation was obtained for swine manure-based carbons activated for 30min at 3ml/min, with 54.3%, 18.9% and 18.1% for copper, cadmium and zinc ions, respectively. BET surface areas for the swine manure-based granular activated carbons ranged between 342 and 456 m2/g but no relationship was found between BET and adsorption. From the physical, chemical and adsorptive data gathered in this study it is suggested that chemisorption is the predominant method by which the carbons are able to adsorb the positively charged metal ions. The authors postulate that negatively charged phosphate groups attached to the carbon skeleton are, at least in part responsible for their increased affinity towards positively charged metal ions. It is believed that the conversion of over abundant and worldwide environmentally-problematic swine manure to activated carbon could represent a novel approach to animal waste utilization.