Less than one percent of all the water on earth is available for human consumption. In this study we focus on the conversion of avocado pits to activated carbons for the adsorption of oxytetracyline, a pharmaceutical compound frequently encountered in wastewater. California-grown Haas Avocado pits were dried in an oven at 110�C for 48 hours, ground and sieved into two particle size fractions (125�m-250�m; 1mm-2.38mm). Particles were pyrolyzed at 10�C/min up to 600�C and held for 30 minutes. Samples were physically activated under CO2 at 700, 800, or 900�C and chemically activated with potassium hydroxide at 500, 600 or 700�C. For the small particle size, we see an approximately doubling in surface area (from 350 to 650 to 1050 m2/g) for each 100�C increment for KOH activation, and a similar trend (250, 600, 980 m2/g) for the larger particle size. As activation temperature increases for CO2 activation, surface areas increase in a similar manner. However, the trend in adsorption capacity measured by adsorption isotherms for oxytetracycline for CO2-activated biochars is considerably more exaggerated; the adsorption capacity for small particles activated at 800�C is tenfold what it is for 700�C activated biochars (0.02 versus 0.2 grams oxytetracycline per gram biochar for 800 and 700�C samples, respectively), and for KOH-activated small particle chars, we see a capacity of 0.05, 0.09 and 0.24 grams oxytetracycline per gram biochar for the 500, 600 and 700�C-activated samples, respectively. Through flow experiments, we confirm that the oxytetracycline does not leach from the biochars once adsorbed under standard conditions. In on-going isotherm and flow experiments, we explore the relationships between particle size, surface area and diffusion limitations for oxytetracycline adsorption, as well as the competitive adsorption between oxytetracyclince and sulfamethoxazole for sites among the avocado pit activated biochars.

Fabrication of activated biochars from avocado pits and their adsorption capacity for oxytetracycline from wastewater

248th National Meeting (2014)

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