Removal of fluoride, cadmium and triclosan from water using bone chars from an invasive species: Optimization, equilibrium and adsorption mechanisms

Abstract

The bone char used in this study was synthesized from devilfish, an invasive species, as an alternative source of raw material for use as an adsorbent for fluoride, cadmium and triclosan from water. Response surface methodology (RSM) was employed to optimize the synthesis conditions such as temperature and pyrolysis time in a tube furnace, ranging from 600 to 800 °C and 1–3 h, respectively. The maximum experimental adsorption capacities of fluoride, cadmium and triclosan (qF, qCd and qTCS) were 7.41, 124.59 and 6.26 mg g−1 obtained at temperatures and times of 600 °C and 1 h, 600 °C and 3 h and 700 °C and 1 h, respectively. The maximum %Y was 70.26 % obtained at 600 and 3 h. Analysis of variance revealed the significance of the synthesis temperature on the adsorption capacities and yield, while the oven residence time was not significant. It was predicted from a multi-objective statistical model that the optimal temperature and time conditions of 627 °C and 3 h maximize the values of %Y, qF, qCd and qTCS corresponding to 68.7 %, 6.47, 117 and 4.35 mg g−1, respectively. The physicochemical and textural properties of the bone char indicated a basic and mesoporous surface. TGA, FT-IR, SEM, and EDS analyses confirmed the adsorption of fluoride and cadmium by electrostatic attractions, ion exchange, and chemisorption, while triclosan was attributed to Van der Waals forces, H-bond and π-π interactions due to the nature of its structure. These results highlight the versatility of devilfish bone char for the removal of anions, cations, and organic compounds, suggesting its potential as a management alternative for this invasive species.

Keywords

• Adsorption
• Bone char
• Devilfish
• Experimental design
• Optimization
• Response surface