Preparation of Porous Biochars by the Co-Pyrolysis of Municipal Sewage Sludge and Hazelnut Shells and the Mechanism of the Nano-Zinc Oxide Composite and Cu(II) Adsorption Kinetics

Xi Chen,Ran Zhang,Mingchuan Zhang,Haibo Li,Bing Zhao,Xinyang Xu,Guangjian Fan

doi:10.3390/su12208668

Abstract

Municipal sewage sludge (MSS) and hazelnut shells were selected for co-pyrolysis and chemically activated with K2CO3 in a N2 atmosphere. The biochar was then modified by photocatalysis. Hazelnut shells, as a solid waste, were selected as a carbon source additive because of its high cellulose content and similar structure to natural wood. Using hazelnut shells could increase the specific surface area, enhance the porosity, and improve the adsorption capacity of the biochar. Hazelnut shells could also reduce the content of heavy metals in the raw biochar materials, along with increasing the ecological security of biochar and contributing to its further development and utilization. FTIR was used to study the changes in the functional groups on the biochar surface. The layered porous structure of the biochar was observed by SEM. The Cu(II) adsorption capacity of the biochar was 42.28 mg/g after 24 h. The Langmuir and pseudo-second-order models effectively described Cu(II) adsorption.

Highlights

In recent years, the number of sewage treatment plants has increased
At the final pyrolysis temperature of 850 ◦C, the yield of biochar decreases to 37.76%, the weight loss is 62.24%, and the iodine adsorption value of the biochar reaches the maximum value, which indicates that the activation temperature of K2CO3 is 850 ◦C for the co-pyrolysis of Municipal sewage sludge (MSS) and hazelnut shells
The pyrolysis temperature led to important changes in the functional groups, and the biochar underwent graphitization above 850 ◦C

Summary

Introduction

The construction and operation of a large number of sewage treatment plants enable the effective control of municipal sewage and industrial wastewater. A large amount of sludge produced by sewage treatment plants is not properly treated, which causes serious environmental problems [1]. Sludge from sewage treatment plants is rich in microbial organic matter, thereby increasing the number of microbial organisms [2] and pollutants in sewage. It contains a large amount of organic-inorganic carbon, nitrogen, phosphorus, potassium and other nutrients and organic matter, parasite eggs [3], heavy metals [4] and other toxic and harmful substances. The process of high temperature dry distillation and pyrolysis of sludge refers to the process method of coal pyrolysis of sludge after drying and drying to produce combustible gas, tar, phenol, acetone, methanol and other chemical raw materials

Methods

Results

Conclusion