H2 produced by catalytic reforming of acetic acid over Ni/char catalyst recycled from the biochar adsorption purification of simulated Ni electroplating wastewater

Abstract

• Double-green of purifying electroplating Ni wastewater and producing H 2 was realized. • Surface complexation and ions exchange mechanisms of biochar promoted Ni 2+ removal. • The recycled Ni on biochar increased the H 2 yield by 15 times. • Two-step activation of steam and H 2 greatly improved double-green performance. • Steam activation increased surface area, Ni dispersion and surface Ni amount. The new method of using biochar to purify nickel-simulated electroplating wastewater and subsequent preparation of a Ni-based catalyst to produce H 2 in bio-oil reforming reaction is proposed. This process aims to realize the double-green of wastewater treatment and H 2 production. Different types of biochar (rice straw, rice husk and cotton stalk) were used. The results indicated that rice straw char (RSC) performed the highest Ni 2+ removal efficiency due to ash components' high ion exchange capacity and high complexation ability of oxygen-containing functional groups. Then the adsorbed RSC was reduced and recycled to prepare Ni/RSC catalyst. Compared with the unadsorbed RSC, the recycled metal Ni remarkably improved the catalytic activity. The average carbon conversion of acetic acid at 600 °C was increased to 76.26% and H 2 yield was increased by 15 times. To further enhance the double-green performance, a two-step activation process was implemented. The biochar was firstly corroded by steam addition (5%, 15% and 25%) and then the adsorbed biochar was reduced by H 2 . After that, the surface area, oxygen-containing functional groups and exchangeable cations of biochar were remarkably enhanced, which increased the Ni removal efficiency to reach 100%. Besides, the formed metal Ni with the higher metal dispersion and smaller Ni particle size improved the reforming of acetic acid. The activation by adding 25% steam further improved carbon conversion by 13.34% and H 2 yield by 60.47%.