Preparation of Mulberry Branch Biomass Char and Its Usage in Wastewater Treatment

Biomass char was prepared from mulberry branches by physical activation. An examination by Fourier transform infrared spectroscopy (FTIR) indicated that the functional groups of Si-O were mostly burnt out, significantly decreasing the ash content. Analysis of data from a scanning electron microscope (SEM) and a Brunauer-Emmett-Teller (BET) test also revealed increased surface roughness and pore structure, which improved the adsorption capacity of biomass char after preparation. The optimum conditions for preparation were found to be pyrolysis at 700 °C for 30 minutes, and then activation at 750 °C for one hour, with 3.4% steam content for the activating agent. The prepared biomass char was then employed to adsorb ammonium, copper(II) actetate [Cu(II)] and hexavalent chromium [Cr(VI)] in a solution. The results indicated that the prepared biomass char had a better adsorptive performance than the raw material. Moreover, the removal of determinands increased along with the dosage, and the highest adsorption efficiency of ammonium, copper(II) acetate [Cu(II)] and hexavalent chromium [Cr(VI)] were found to be 20%, 100% and 50%, respectively. The adsorptions of ammonium and hexavalent chromium [Cr(VI)] can be simulated by a pseudo-second order model, while the adsorption of copper(II) acetate [Cu(II)] is better simulated by a pseudofirst order model. The adsorption isotherms of copper(II) acetate [Cu(II)] by biomass char were also investigated, and the Langmuir isotherm was found to best describe the adsorption process.