Wheat Straw-Based NaOH-Activated Biochar for Tetracycline Adsorption from Water: A Study on the Effect of Chemical Activation on Its Process Efficiency

Wheat straw (WS) is a potential biomass having no economic value but has vast environmental consequences. Valorization of WS to its biochar (WS-BC) with further NaOH activation (WS-NBC) was fabricated and employed as an adsorbent to eliminate tetracycline (TTC) from contaminated solution. The process fabrication was an initial pyrolysis under N2 atmosphere at 450 ℃ to form WS-BC followed by its impregnation with NaOH to form WS-NBC. Characterization studies revealed the successful fabrication of activated biochar having favourable surface functionalities and well-defined porosity as per FTIR and BET studies. Batch adsorption tests conducted under operating conditions of 10 ppm of TTC, adsorbent dosage of 1 g/L, for a contact duration of 30 min and at neutral pH revealed 89% removal efficiency. Adsorption tests revealed not only fast kinetics but also there was a requirement of very low adsorbent for bringing about high TTC removal efficiency. The adsorbent-adsorbate system followed the Langmuir model implying monolayer adsorption and highest capacity was observed as 35 mg/g. Another significant aspect was the successful regeneration of the adsorbent showing a total loss of 8% efficiency after 5 consecutive cycles of operation. The study has demonstrated the potential of chemical activation on the physicochemical as well as on the TTC removal efficiency of WS-based adsorbents.