In this study, avocado seed was successfully used as raw material for producing activated carbons by conventional pyrolysis. In order to determine the best condition to produce the activated carbons, a 2 full-factorial design of experiment (DOE) with three central points was employed by varying the temperature and time of pyrolysis. The two evaluated factors (temperature and time of pyrolysis) strongly influenced the S, pore volumes, hydrophobicity-hydrophilicity ratio (HI) and functional groups values; both factors had a negative effect over S, pore volumes and functional groups which means that increasing the values of factors leads to decrease of these responses; on the other hand, with regards to HI, both factors caused a positive effect which means that increasing their values, the HI has an enhancement over its values. The produced activated carbon exhibited high specific surface areas in the range of 1122-1584 m g. Surface characterisation revealed that avocado seed activated carbons (ASACs) have hydrophilic surfaces and have predominantly acidic groups on their surfaces. The prepared ASACs were employed in the adsorption of 25 emerging organic compounds such as 10 pharmaceuticals and 15 phenolic compounds which presented high uptake values for all emerging pollutants. It was observed that the activated carbon prepared at higher temperature of pyrolysis (700 °C), which generated less total functional groups and presented higher HI, was the activated carbon with higher sorption capacity for uptaking emerging organic contaminants. Based on results of this work, it is possible to conclude that avocado seed can be employed as a raw material to produce high surface area and very efficient activated carbons in relation to treatment of polluted waters with emerging organic pollutants.

Azo dyes are one of the synthetic dyes that are used in many textile industries. Adsorption is one of the most effective techniques for removal of dye-contaminated wastewater. In this work, efficiency of multiwalled carbon nanotubes (MWCNTs) as an adsorbent for removal of Acid Red 18 (azo-dye) from aqueous solution was determined. The parameters affecting the adsorption process such as contact time, pH, adsorbent dosage, and initial dye concentration were studied. Experimental results have shown by increasing the adsorbent dosage, the rate of dye removal was increased, but the amount of adsorbed dyes per mass unit of MWCNTs was declined. pH as one of the most important influencing factors on the adsorption process was evaluated. The best pH for adsorption process was acidic pH of about 3. To describe the equilibrium of adsorption, the Langmuir, Freundlich and Temkin isotherms were used. The Langmuir isotherm (R2=0.985) was the best fitted for experimental data with maximum adsorption capacity of 166.67 mg/g. A higher correlation value of the kinetic's model was observed close to pseudo second order (R2=0.999) compared to other kinetic models.

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