Adsorption of Organic Constituents from Reverse Osmosis Concentrate in Coal Chemical Industry by Coking Coal

Hongxiang Xu,Kejia Ning,Penghui Wang,Rong Zhao,Gen Huang,Jiushuai Deng,Qizheng Qin,Changfeng Zhang

doi:10.3390/pr7010044

Abstract

To solve the unwieldy problem of coal chemical wastewater reverse osmosis concentrate (ROC), a novel treatment method in which coking coal was used to adsorb the organic from ROC and the adsorption mechanism involved was investigated. The results showed that the organic components in the ROC of coal chemical industry can be effectively absorbed by the coking coal and the total organic carbon, UV254 and chromaticity of treated ROC reduced by 70.18%, 70.15% and 59.55%, respectively, at the coking coal dosage of 80 g/L. The isothermal adsorption data were fitted to the Langmuir model well. The kinetics were expressed well by the quasi-second-order kinetic model. The intragranular diffusion model and the BET (Acronym for three scientists: Brunauer–Emmett–Teller) test showed that the adsorption occurred mainly on the surface of the coking coal and its macropores and mesopores. When the pollutants further diffused to the mesopores and micropores, the adsorption rate decreased. The result of X-ray photoelectron spectroscopy and fourier transform infrared spectroscopy spectra showed that the coking coal mainly adsorbed the nitrogen and oxygen species and the halogenated hydrocarbon organic compounds in the ROC. The chlorinated hydrocarbons and heterocyclic organics in ROC are adsorbed on the surface of coking coal.

Highlights

Regarding coal chemical wastewater, especially its reverse osmosis concentrate (ROC), there are serious membrane fouling, serious equipment corrosion and difficult crystallization purification during the processing
As the coking coal dosage increased from 6.67 g/L to 80 g/L, the adsorption capacity decreased from 7.09 mg/g to 2.9 mg/g
There was no change in Cl− concentration and Electrical conductivity (EC) value, because of coking coal is difficult to adsorb polar substances; UV254 and chromaticity decrease significantly with the increase of adsorbent addition When coking coal dosage was 80 g/L, UV254 decreased from 9.42 Abs to 3.77 Abs and the chromaticity decreased from 1243 PCU to 271 PCU, with removal rates of 70.15% and 59.55%, respectively

Summary

Introduction

Especially its reverse osmosis concentrate (ROC), there are serious membrane fouling, serious equipment corrosion and difficult crystallization purification during the processing. Due to its complex composition, high halogen content and its considerable biological toxicity by organic components [1], treatment of ROC is obstacle to zero discharge of coal chemical enterprises, which needs to be solved urgently. The ROC processing technologies were actively researched many fields, such as desalination, municipal sewage treatment, industrial sewage treatment and so on. The ROC processing technologies including membrane treatment, biological treatment and advanced oxidation technology. With the application of online coagulation-ultrafiltration pretreatment technology, some organic components were removed under laboratory conditions [2]. The electrodialysis solution for seawater desalination ROC was proposed [3]

Methods

Results

Conclusion