Adsorption of pharmaceuticals from aqueous solutions using biochar derived from cotton gin waste and guayule bagasse

Abstract

Biochars produced from cotton gin waste (CG) and guayule bagasse (GB) were characterized and explored as potential adsorbents for the removal of pharmaceuticals (sulfapyridine-SPY, docusate-DCT and erythromycin-ETM) from aqueous solution. An increase in biochar pyrolysis temperature from 350 οC to 700 οC led to an increase in pH, specific surface area, and surface hydrophobicity. The electronegative surface of all tested biochars indicated that non-Coulombic mechanisms were involved in adsorption of the anionic or uncharged pharmaceuticals under experimental conditions. The adsorption capacities of Sulfapyridine (SPY), Docusate (DCT) and Erythromycin (ETM) on biochar were influenced by the contact time and solution pH, as well as biochar specific surface area and functional groups. Adsorption of these pharmaceutical compounds was dominated by a complex interplay of three mechanisms: hydrophobic partitioning, hydrogen bonding and π–π electron donor–acceptor (EDA) interactions. Despite weaker π–π EDA interactions, reduced hydrophobicity of SPY− and increased electrostatic repulsion between anionic SPY− and the electronegative CG biochar surface at higher pH, the adsorption of SPY unexpectedly increased from 40% to 70% with an increase in pH from 7 to 10. Under alkaline conditions, adsorption was dominated by the formation of strong negative charge-assisted H-bonding between the sulfonamide moiety of SPY and surface carboxylic groups. There seemed to be no appreciable and consistent differences in the extent of DCT and ETM adsorption as the pH changed. Results suggest the CG and GB biochars could act as effective adsorbents for the removal of pharmaceuticals from reclaimed water prior to irrigation. High surface area biochars with physico-chemical properties (e.g., presence of functional groups, high cation and anion exchange capacities) conducive to strong interactions with polar-nonpolar functionality of pharmaceuticals could be used to achieve significant contaminant removal from water. Graphic Abstract

Removal of Pharmaceutical Micropollutants with Integrated Biochar and Marine Microalgae

“…Based on the Langmuir isotherm ( Table 6 ), the maximum adsorption capacities (q m , mg g −1 ) were 16.6 (CBZ), 13.9 (SMT) and 9.7 (TRA), and the R 2 values were 0.918, 0.904 and 0.902, respectively. Ndoun et al [ 44 ] reported a q m value of 17 mg g −1 , and Kim et al [ 51 ] reported a value of 0.99 for the removal of PPCPs by biochar, which are nearly equal to the findings of the current study. where x/m is the adsorbed the mass of the adsorbate (mg g −1 ), a and b are empirical constants and C e denotes the adsorbate concentration after the adsorption process (mg L −1 ).…”

“…Based on the Freundlich isotherm, the maximum adsorption capacities (K f , mg g −1 ) were 0.39 (CBZ), 0.31 (SMT) and 0.26 (TRA), and the R 2 values were 0.921, 0.913 and 0.931, respectively. Ndoun et al [44] reported a K f value of 0.33 mg g −1 , and Kim et al [51] reported a value of 0.93 for the removal of PPCPs by biochar, which are consistent with the findings of the current study. Therefore, both isotherms could explain PPCP removal by biochar.…”

“…These results can be explained by the adsorption of PPCPs by biochar as well as improvement in the microalgal community in the presence of biochar. Ndoun et al [ 44 ] removed 40% of pharmaceutical by biochar at neutral pH. Magee et al [ 45 ] stated that biochar can absorb nutrients on its surface and attracts and immobilises algae on its surface.…”

Impacts of temperatures and phosphoric-acid modification to the physicochemical properties of biochar for excellent sulfadiazine adsorption

“…Among these approaches, adsorption has become one of the most widely accepted technologies due to its economy, feasibility and environmental-friendliness (Gao et al 2012;Hu et al 2020;Kim et al 2020;Ling et al 2016;Xiao et al 2018). Based on the characteristics of high porosity, hydrophobicity and aromaticity (Peiris et al 2017), biochars (BCs) have attracted extensive attention as an excellent adsorbent for removing organic contaminants (Dai et al 2020;Hopkins and Hawboldt 2020;Ndoun et al 2020;Tan et al 2015;Yao et al 2020). BCs are the pyrolysis products of biomasses at low temperatures (< 800 °C) in the oxygen-limited environment (Tripathi et al 2016).…”

Detoxification of Ciprofloxacin in an Anaerobic Bioprocess Supplemented with Magnetic Carbon Nanotubes: Contribution of Adsorption and Biodegradation Mechanisms

“…The adsorption of CIP onto the sludge is a spontaneous, exothermic and a linear process that includes both physisorption and chemisorption [ 10 , 11 ]. As mentioned above, at neutral pH, CIP mainly presents zwitterionic form (CIP ± ) with –NH 2+ and –COO − groups [ 49 , 62 , 63 ]. The functional groups present on anaerobic sludge, such as C–O, C–O–C, N–H, O–H and COOH provide binding sites for CIP ± adsorption [ 10 ].…”