Determination and removal of phenolic compounds from drinking water of Jimma town by using avocado kernel seed adsorbents

Abstract

Phenolic compounds are a versatile precursor to a large collection of drugs most notably aspirin, various herbicides and pharmaceuticals. However, these compounds are considered as priority pollutants since they are harmful to organisms’ especially human and aquatic life, it is toxic when present in elevated levels and to be carcinogens. Therefore, removing phenols and their derivative from drinking water is an essential task to safe the water. Thus, the objective of this study was to determine the level of phenolic compounds and compare the adsorption capacity of both AC-1 and AC-2 prepared from avocado kernel seeds by adsorption onto drinking water in Jimma town. For adsorption process cleaned and washed avocado kernel seeds(per sea americana) were dried at 100 °c in an oven overnight and carbonization was carried out by increasing the furnace temperature at a rate of 5 °C/min to a final temperature of 800 °C for 160 minutes. Then, the activated carbon was sieved, washed with distilled water until the solution pH reached 7.0. Optimization of activated carbon was done through effects of solution pH, contact time; initial phenol concentration and temperature on the adsorption From the analysis of water using 4-Aminoantipyrine (4-AAP), it was found that treated and system distributed water has more phenolic compounds as compared to untreated water due to the presence of chlorination after disinfection. The kinetic studies for the adsorption process were also carried out by checking various models and the data obtained was best fitted to pseudo-second order kinetic model. The isotherms models were analyzed with Langmuir, Freundlich and Temkin to validate the adsorption process. It was found that Langmuir model was best fitted to the obtained result for both adsorbents. Thermodynamic parameters were calculated for adsorption process and the result showed that the values of ΔG, ΔH, and ΔS are – 13.6 kJ/mol, - 69.36 kJ/mol and – 181.04 J/K at 303 K. Thus, it could be summarized that the adsorption of phenol compounds are spontaneous, chemisorbed, monolayer and exothermic on activated carbon prepared from avocado kernel seeds. Key words: Chemisorbed, monolayer, carbonization, activated carbon, adsorption, raw water, system distributed water.