Abstract
The non-toxic and completely biodegradable cellulose within bamboo is one of the most abundant agricultural polysaccharide wastes worldwide, and can be processed into cellulose nanofibres (CNFs). Iron(III)-loaded CNFs (Fe(III)@CNFs) derived from bamboo were prepared to improve the adsorption of tetracycline (TC), chlortetracycline (CTC) and oxytetracycline (OTC) from an aqueous solution. The preparation conditions of Fe(III)@CNFs suitable for the simultaneous adsorption of three tetracycline antibiotics (TCs) were investigated. Various analyses proved the abundance of oxygen-containing functional groups and the existence of Fe(III) active metal sites in Fe(III)@CNFs. In batch experiments, Fe(III)@CNFs were applied under a wide pH range and the maximum adsorption capacities were 294.12, 232.56 and 500.00 mg g−1 (for TC, CTC and OTC, respectively). In addition, different concentrations and types of coexisting anions have a weak effect on TCs adsorption. The original TCs adsorption capacities of Fe(III)@CNFs remained stable (greater than 92%) after five cycles when UV + H2O2 was used as the regeneration method. Four adsorption mechanisms (surface complexation, hydrogen bonding, electrostatic interaction and van der Waals force) were obtained for the endothermic adsorption of TCs, among which surface complexation between Fe(III) and TCs always dominates. The practically applicable Fe(III)@CNFs adsorbents are promising for TCs enrichment and remediation in engineering applications.
Highlights
Numerous approaches have been used to remove tetracycline antibiotics (TCs), including biodegradation [14], membrane filtration [15], electrochemical oxidation [16], photolysis [17], photocatalysis [18,19], catalysis [20], ozonation [21] and adsorption [22]
The TCs adsorption capacities of cellulose nanofibres (CNFs) modified with the iron salt were significantly higher than those of CNFs modified with the other two metal salts
The TCs adsorption capacities of CNFs modified with the iron salt were 3.3 times (TC), 1.9 times (CTC) and 3.7 (OTC) times higher than those of CNFs modified with the aluminium salt, and they were 6.5 times (TC), 31.7 times (CTC) and 4.3 times (OTC) higher than those of CNFs modified with the manganese salt
Summary
Numerous approaches have been used to remove TCs, including biodegradation [14], membrane filtration [15], electrochemical oxidation [16], photolysis [17], photocatalysis [18,19], catalysis [20], ozonation [21] and adsorption [22]. The pH of the actual wastewater is usually neutral, and pH regulators must be added to minimize pH if adsorbents cannot achieve a high adsorption capacity in neutral environment This addition can lead to an increase in operating costs; studies on the economic and environmentally friendly CNFs modification methods remain a trend. Luo et al [37] optimized the adsorbent preparation method (mechanical shearing method), which is simpler and less expensive than the TEMPO reagent method to prepare CNFs, and developed the second-generation iron-loaded nanocellulose Both the ferric loading and mechanical shearing method reduce the adsorption cost of modified CNFs. Currently, the interaction between iron and TCs has been confirmed [30], but no study is available on TCs adsorption through iron(III)-loaded CNFs (Fe(III)@CNFs). A renewable and non-sintered adsorbent with stable adsorption performance is desired to solve the scientific problem of simultaneous adsorption of TC, CTC and OTC
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