Effective use of activated carbon from olive stone waste in the biosorption removal of Fe(III) ions from aqueous solutions

Abstract

The pollution of industrial wastewater by heavy metals introduces a large number of iron ions, which constitute a hazard to human life even at trace concentrations. Most processes for the treatment of wastewater with Fe(III) ions and others heavy metals today are based on chemical physical methods. They have the disadvantage of generating a secondary sludge, which always requires additional treatment. This makes the heavy metal removal process more expensive. In contrast, the biosorption process has proven in recent years to be an alternative, economical and efficient process for the treatment of wastewater that is contaminated by metals. This paper proposes the use of Multi-Response Surface with desirability functions (MRS) to optimize the process of biosorption using activated carbon from olive stone waste to remove Fe(III) ions from aqueous solutions. The study has been validated on a laboratory scale, is not technically demanding, is environmentally friendly and involves a cost that will be acceptable to the industrial wastewater for economic reasons. Several parameters or inputs of the biosorption process were considered. They included the initial iron concentration, biosorbent dosage, process temperature, agitation time and mixing speed. However, the concentration of Fe(III) ions that are present in the treated wastewater is the variable to optimize in three optimization scenarios when the minimum, mean and maximum values of initial iron concentration appear in their study range (lower, intermediate and higher value). These scenarios were based on a desire to obtain the maximum elimination of Fe(III) for any value of parameters or inputs of the biosorption process, maximum elimination of Fe(III) when the energy consumption of the adsorption process was minimized, and maximum elimination of Fe(III) when the biosorbent dosage was minimized. The proposed adsorption process achieved a maximum Fe(III) elimination of 99.51%, 99.24% and 99.49% for the first, second and third optimization scenarios respectively when, in all cases, the initial iron concentration was 55 mg/L. Agreement between the experimental and predicted results indicates that activated carbon that is derived from olive stone waste can be used as a biosorbent.