Engineered pine nut shell derived activated carbons for improved removal of recalcitrant pharmaceuticals in urban wastewater treatment

• Published in: Journal of hazardous materials 2022-09, Vol.437, p.129319-129319, Article 129319
• Main Authors: Mestre, Ana S., Viegas, Rui M.C., Mesquita, Elsa, Rosa, Maria João, Carvalho, Ana P.
• Format: Article
• Language: English
• Subjects: Adsorption and adsorption modelling; Pharmaceutical compounds; Pine nut shell; Steam activated carbons; Wastewater treatment
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2022.129319

Novel powdered activated carbons (PACs) from pine cones and pine nut shells (PNSs) were tested for the competitive adsorption of pharmaceutical compounds (PhCs) in spiked (100 µg/L) secondary effluent and mixed liquor from an urban wastewater treatment plant. Steam activated PNS77, with hierarchical pore structure and 1463 m2/g of BET area, outperformed the commercial benchmark (WP220, mineral origin) for PhCs and dissolved organic matter (DOM) control. PNS77 attained the highest adsorption capacity and rate in synthetic and real wastewaters. Competitive adsorption isotherms revealed the detrimental effect of direct site competing DOM on PhC removal. The PhCs’ adsorbability increased with their hydrophobicity, regardless of the water matrix. Kinetic data allowed inferring that indirect competition due to pore constriction/blockage appeared to occur only in mixed liquor. Adsorption isotherm data modelling for ng/L range revealed 80 % removal of carbamazepine and diclofenac would be achieved dosing 8–15 mg/L PNS77 to secondary effluent, while for mixed liquor the dose must be doubled to balance the increased competition. Hydrophilic sulfamethoxazole required a higher dose (34–44 mg/L), lower in the mixed liquor. PNS77 hierarchical pore network and basic surface chemistry minimized DOM direct site competition, requiring lower doses in practical applications for wastewater treatment. [Display omitted] •Pine nut shell steam activation yields an alkaline, hierarchically structured PNS77.•PNS77 outperforms commercial PACs for pharmaceuticals removal from urban wastewater.•PNS77 pore network and net charge better controls DOM direct site competition.•Kinetic data modelling only identifies competition by pore blockage in mixed liquor.•Mixed liquor biomass doubles PAC dose for CBZ/DCF and lowers it for hydrophilic SMX.