Mn-Embedded Porous Rubber Seed Shell Biochar for Enhanced Removal of Copper Ions and its Ingeniously Re-Functionalizing

Abstract

Using some metals and their oxides modified biochar adsorbents to purify copper-containing wastewater is effective. However, the degraded reuse performance of waste adsorbents prevented their large-scale application. Thus, in this work, a MnO x -modified porous biochar was firstly obtained by KMnO 4 activation of rubber seed shell wastes for Cu(II) ions removal, and then the waste adsorbent was skillfully constructed to Cu-Mn bimetallic catalyst for efficient selective hydrogenation of furfural, realizing the proper disposal of waste adsorbent. The adsorption experiments showed that the optimized Mn-modified biochar (i.e. Mn 18% - rss BC) had a good purification capacity for the Cu(II)-containing wastewater with a wide pH range and high strong resistance to some common coexisting ions, and the maximum adsorption capacity of Cu(II) could be up to 200.59 mg/g. The characterization results showed that the oxygen-containing functional groups and a large number of MnO x particles on the surface of Mn 18% - rss BC could form stable complexes with Cu(II), making it exhibit efficient and spontaneous multilayer adsorption behavior. In addition, after the reduction of the waste adsorbent, the Cu and Mn species on the surface were uniformly dispersed in the porous carbon in the form of electron-rich nano-polycrystalline aggregates at about 3.5 nm. Under the optimized conditions, the obtained catalyst (i.e., Cu 14.3 Mn 16.5 - rss BC) had high catalytic efficiency, which can achieve 100% of furfural conversion and 87.06% of furfuryl alcohol selectivity. In conclusion, this work provided a composite solution for the reuse of copper-containing waste adsorbent, the resource recovery of agricultural and forestry wastes and the efficient transformation of biomass platform compounds.

Keywords: biochar, Manganese oxide, Cu(II), Adsorption, Furfural hydrogenation