| Summary: | The objective of this investigation was to evaluate pecan and almond shell-based granular activated carbon's viability to effectively remove organic and inorganic pollutants in municipal wastewater compared to commercial carbons, Filtrasorb 200 (bituminous coal-based), and GRC-20, 206C AW (coconut shell-based). The solution to the objective was approached under three distinct phases, namely (I) physical and chemical characterization of the pecan and almond shell-based experimental and bituminous coal and coconut shell-based commercial granular activated carbons; (II) treatment of organic contaminants in municipal wastewater by experimental and commercial GACs; (III) treatment of inorganic contaminants in municipal wastewater by experimental and commercial GACs.
Phase I study showed that the almond shell-based chemically activated carbon (ALA) had the largest total surface area (1340 m<sup>2</sup>/g) including the commercial carbons. The bulk densities of both physically and chemically (0.49 to 0.57 g/m<sup>3</sup>) -activated pecan shell-based carbons were comparable to those of commercial carbons (0.49 to 0.54 g/m<sup>3</sup>). ALA had the highest attrition (31.68%) compared to chemically activated pecan shell-based carbon (PSA) with lowest attrition (7.10%). PSA also contained the lowest ash, a desirable attribute. Activation affected conductivity. Chemical activation lowered conductivity when compared to physical activation. Multivariate analysis showed that steam- and acid-activated pecan shell-based carbons (PSS and PSA) had more similarity to commercial carbons.
Phase II study showed that PSS had higher adsorptive capacity towards Chemical Oxygen Demand (COD) than carbon dioxide-activated pecan shell-based carbon (PSC) and commercial carbons. Activation methods of the carbons affected the pH. The study on adsorption of volatile organic compounds (VOCs) showed that all the experimental carbons exhibited efficient adsorbability of benzene and other halogenated aliphatic compounds under study. Multivariate analysis indicated, PSS and PSA to be similar in terms of overall VOC adsorption.
Phase III study showed that the PSS with higher log x/m (solute adsorbed/ carbon dosage) ratio and log Ce ranging from 0.5 to 1.0 g/100 ml is most suitable for the adsorption of Cu<sup>2+</sup>. However, within the four carbons used for the adsorption of Pb<sup>2+</sup> and Zn<sup>2+</sup>, PSA was found to be more effective compared to PSS and PSC.
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