Application of statistical response surface methodology for optimization of fluoride removal efficiency by Padina sp. alga

Human exposure to fluoride in drink water at a level above 1.5 mg/L causes a lot of health problems. The present study was carried out to assess the fluoride biosorption capability of Padina sp. alga as biosorbent material using conventional one-factor-at-a-time (OFAT) and Box-Behnken design to optimize the process. By OFAT, fluoride uptake was significantly affected by pH, time, fluoride concentration, and biosorbent dose (p-value < 0.05) and the highest fluoride biosorption (85.95%) was recorded at pH 7, time 60 min, fluoride concentration 2 g/L, and an adsorbent dose 30 g/L. Based on the Box-Behnken design, the quadratic model was developed to correlate the variables to the response. By Analysis of Variance (ANOVA), the model was statistically significant (p-value < 0.05). It was suggested that optimal values of pH, time, fluoride concentration, and biosorbent dose were 5, 90 min, 3 mg/L, and 30 g/L, respectively, and fluoride removal at these optimum conditions was 94.57%. For application, Padina sp. was removed from 67.79% to 78.78% of fluoride in collected groundwater samples. It was concluded that the Padina sp. could be used as eco-friendly biosorbent for fluoride and response surface methodology was more applicable and effective in optimization to obtain the highest removal efficiency of fluoride by Padina sp. PRACTITIONER POINTS: The fluoride biosorption was studied using Padina sp. alga as an eco-friendly biosorbent. By one-factor-at-a-time (OFAT), the highest fluoride biosorption rate was 85.95%. Response surface methodology was suggested that maximum Fluoride removal at optimum condition was 94.57%. Statistical response surface methodology was more applicable, effective in optimization and considered the interaction between factors.