Arsenic and lead removal from water using whey protein blend membranes procured by thermal denaturation and electrospinning

Globally, millions of people are exposed to elevated concentrations of heavy metals in drinking water and groundwater, thus representing an important environmental and public health problem. Among these inorganic species, arsenic and lead are recognized as a challenging concern because they are naturally occurring and anthropogenic-based cumulative pollutants that can lead to the failure of multiple human body systems and eventually fatality. However, water quality suffers also from the occurrence of organic matter discharged mainly by the food sector, which is the case for whey, a by-product of the dairy industry. Therefore, there is an opportunity to recover whey from bleed and waste streams to reduce water sources’ organic load, while repurposing it to develop novel materials for water treatment, especially heavy metal removal, given their previously reported affinity with protein-based resources. This research reports the preparation, characterization, and evaluation of two adsorptive materials based on whey protein amyloids for arsenic and lead adsorption from water. The first composite was prepared via electrospinning of a polymer blend of enzymatic-denatured whey amyloids and polycaprolactone (WPId/PCL), while the second comprised an activated carbon-modified with whey amyloids obtained by thermal denaturation at acidic conditions (AC/WPF). A Box-Behnken design was used to obtain optimum preparation formulation and process parameters for the electrospun composite. The results demonstrated that PCL and WPId content were determined as significant factors governing fibre diameter and lead adsorption capacity, respectively. Adsorption capacities ranged between 8.9 and 20.8 mg g-1. On the other hand, AC/WPF was tested for arsenic removal through batch adsorption kinetics and isotherms at optimal pH 5.0. The results showed maximum arsenate adsorption capacities of 12.38 mg g-1, 13.18 mg g-1 and 13.58 mg g-1 for 20, 30 and 40 °C, respectively, calculated by the Sips model. Kinetic modelling of arsenate adsorption was successful with the pseudo-second-order model, suggesting that chemisorption could govern the adsorption. Thermodynamic analysis revealed an endothermic process. The participation of whey functional groups via hydroxyl and amide bonding with arsenic was identified as a relevant interaction in the adsorption mechanism. This study highlights the potential of whey protein as a raw material to produce added-value products and its performance as a precursor of novel adsorbents for water purification, therefore minimizing their associated disposal cost and addressing relevant environmental concerns such as arsenic and lead contamination.