Activation of Luffa cylindrica with particulate matter for the removal of fluoride ions from aqueous solutions in a fixed-bed adsorption column

Luffa sponge (fibrous network obtained from mature dried Luffa cylindrica) was activated using particulate materials to increase its adsorption capacity for fluoride ions from aqueous solution. The activation of the Luffa cylindrica with hydroxyapatite (HA) on the surface presented the best efficiency in the removal of fluoride ions. The presence of hydroxides (OH-) as active groups in the Luffa cylindrica structure are responsible for adsorption. In this work, the results of bioadsorption tests of fluoride ions with Luffa cylindrica-HA in fixed-bed columns are presented. The depth of mass transfer zone increased from 5.5 to 11.0 cm, with bed volumes of 4.32 and 8.64 cm3, respectively. The results were treated with various fixed-bed models (Thomas, Yoon-Nelson, Dose- Response and Weibull distribution). The results obtained showed that breakthrough time increases as the bed height increases. The bed capacity was 2.4 mg/g, with the bed depth, influent flow rate and influent concentration of 5.5-11.0 cm, 1 mL/min, and 5 mg/L, respectively. The breakthrough curve matched the Thomas, Yoon-Nelson, Dose-Response, and Weibull, models. The Weibull distribution model was used to predict the breakthrough curve from the experimental results. The results were well fitted to this model and the adsorption capacity was calculated. The study of the operating parameters of the column on a laboratory scale can be used to simulate the potential performance of the adsorbent and extrapolate the results to a pilot scale or larger.

Automated summary

Luffa sponge activated with hydroxyapatite exhibited the highest efficiency in removing fluoride ions. The depth of mass transfer zone increased with bed volumes. The breakthrough curve was successfully fitted with various models, and the Weibull distribution model provided accurate predictions.