Treatment and valorisation of fruit juice wastewater by aqueous phase reforming: Effect of pH, organic load and salinity

Abstract This work analyses the application of aqueous phase reforming as a treatment and valorisation method for fruit juice wastewater enabling production of H2 and alkanes from renewable source. The variables considered were pH, organic load and salinity of wastewater, since they are fluctuant and can affect the performance of biological treatments most commonly used. The experiments were carried out in batchwise, at 493 K and 24–28 bar for 4 h using a 3% Pt/C catalyst. Single compounds (glucose, fructose, citric acid, ascorbic acid, galacturonic acid) and fruit juice wastewater were tested as feedstocks. Organic carbon removal from wastewater was higher in the reforming of glucose and fructose within 7–10 pH range, while for organic acids and fruit juice wastewater a higher removal was obtained at pH 2. H2 yield and selectivity increased at increasing pH, due to better conditions for water-gas shift reaction and abstraction of CO2. H2 production by aqueous phase reforming of fruit juice wastewater was little affected by pH, yielding around 6.6 mmol H2/g initial chemical oxygen demand, in the pH range tested. Alkanes were also produced, with higher proportion of CH4 than other alkanes at high pH (10–12). A wide operation window was observed regarding organic load of fruit juice wastewater, although organic carbon removal declined slightly at the highest loads tested. Salinity did not affect organic carbon removal, while H2 yield decreased from 7.8 to 4.2 mmol H2/g initial chemical oxygen demand at high salinity, probably due to catalyst deactivation. Aqueous phase reforming is proved to be an alternative to biological treatment methods with low sensibility to fluctuations in the characteristics of wastewater.