Harnessing Hydrogen from the Cheese Whey Effluent in Dairy Industry: Aqueous-Phase Reforming of the Model Compound Lactose Using Pt-Ni/Cu-Al Hydrotalcite Catalyst

Abstract

Cheese whey effluent (CWE) is a byproduct from cheese making industry having a high (50,000–100,000 mg/L) chemical oxygen demand (COD) which makes it mandatory to treat this effluent. Unlike the traditional methods known for CWE treatment – fermentation, enzymatic hydrolysis, ultrafiltration, etc., aqueous-phase reforming (APR) is a technology which helps to treat the wastewater by valorising it producing high heating value gases such as hydrogen (H₂), thus achieving a double benefit. In this work, APR of lactose as a model compound from CWE was carried out using a Pt promoted Ni/Htlc catalyst (where Htlc refers to hydrotalcite) in a stirred batch reactor. Experimental trials were performed where the reaction parameters viz. temperature (488–518 K), catalyst loading (2–6 kg/m³), reaction time (1.5–6 h) and lactose concentration (1–5 wt%) were optimized. For optimized parameters, H₂ selectivity of 73% was achieved. The catalyst support Htlc was prepared using Cu and Al, the former being water gas shift (WGS) promoter. Furthermore, the effect of promotion by Pt was investigated with three different loadings (1–5%), where 2.5% Pt outperformed others. The Ni loading was fixed at 10% in all the catalysts. The synthesized catalyst was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) analysis and Fourier transform infrared spectroscopy (FTIR). Finally, based on the experimental data, a rate law was proposed where the rate constant and adsorption constant of lactose were determined using multilinear regression. This work provides a proof-of-concept investigation for valorising CWE via APR using a novel catalyst Pt-Ni/Htlc.