Removal of Benzohydroxamic Acid from Aqueous Solutions Using Multi-Walled Carbon Nanotubes/iron-Doped Hydroxyapatite Composites: Synthesis, Adsorption Performance, and Characteristics

Benzohydroxamic acid (BHA) is the main organic contaminant in tungsten ore processing wastewater and is harmful to the environment and human health because of its stable biochemical properties and high toxicity. In this study, multi-walled carbon nanotube/iron-doped hydroxyapatite composites (MWCNT-COOH/Fe-HAP) were prepared using a wet chemical method, and the removal efficiency of BHA from aqueous solutions was evaluated via batch adsorption experiments. The effects of the adsorbent dosage, initial BHA concentration, pH, temperature, contact time, and ionic strength on the adsorption performance were investigated. The adsorption kinetics study indicated that the adsorption process was more consistent with the pseudo-second-order model and that the adsorption isotherm fit better with the Langmuir model. Thermodynamic studies suggested that the adsorption process is spontaneous, exothermic, and chaos-decreasing. The maximum adsorption capacity of MWCNT-COOH/Fe-HAP for BHA was 27.65 mg & sdot;g-1 attained at pH= 8. MWCNT-COOH/Fe-HAP showed excellent removal efficiency for BHA under the same experimental conditions as other common adsorbents. The adsorption-desorption regeneration experiments showed that MWCNT-COOH/Fe-HAP was stable, and the removal efficiency of BHA only decreased by 10.03% after five regeneration cycles. Based on the experimental data, zeta potential, FTIR, and XPS analysis, the possible adsorption mechanism of BHA mainly involved electrostatic interaction, hydrogen bonding, pi-pi EDA interaction, and coordination between BHA and iron species. This study provides a novel method for removing BHA from wastewater.