Li Huijin, Ding Shuang, Yuan Jie
College of Environmental and Chemical Engineering, Dalian University, Dalian 116622, Liaoning, China.
School of Chemistry and Materials Engineering, Liupanshui Normal University, Liupanshui 553004, Guizhou, China.
ACS Omega. 2023 Mar 24;8(13):12206-12216. doi: 10.1021/acsomega.2c08192. eCollection 2023 Apr 4.
Current research focuses on extracting humic acid (HA) compounds from low-rank coals to obtain high value-added products. In this study, HAs with high purity and low heavy metal content were obtained from lignite by combining acid pretreatment with hydrothermal treatment. Scanning electron microscopy, elemental analysis (EA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, and inductively coupled plasma optical emission spectrometry (ICP-OES) were used to analyze raw lignite and HAs. The effects of acid and hydrothermal treatments on the inorganic elements, functional groups, and yield of HAs were examined. The results showed that acid treatment reduced the ash content of lignite from 20 to 9%, and hydrothermal treatment increased the yield of HAs from 36 to 68%. The chemical properties of HAs exhibited an increase in molecular weight and improved aromaticity after acid and hydrothermal treatments. The results of ICP-OES analysis suggested that the combined method of acid and hydrothermal treatments resulted in a significant reduction of heavy metal elements in HAs. FTIR analysis confirmed the results and demonstrated that the extracted HA from nitric acid pretreated and hydrothermal generation of lignite PHA was rich in carboxyl and phenolic functional groups. PHA was applied to biochar as an activator for the adsorption of heavy metal ions. The experimental results showed that PHA was successfully loaded onto biochar and introduced a large number of functional groups, and the adsorption capacity of the modified biochar for Pb was effectively improved.
当前的研究聚焦于从低阶煤中提取腐殖酸（HA）化合物以获得高附加值产品。在本研究中，通过将酸预处理与水热处理相结合，从褐煤中获得了高纯度、低重金属含量的腐殖酸。利用扫描电子显微镜、元素分析（EA）、傅里叶变换红外（FTIR）光谱、X射线衍射以及电感耦合等离子体发射光谱（ICP-OES）对原始褐煤和腐殖酸进行了分析。考察了酸处理和水热处理对腐殖酸中无机元素、官能团及产率的影响。结果表明，酸处理使褐煤的灰分含量从20%降至9%，水热处理使腐殖酸的产率从36%提高到68%。酸处理和水热处理后，腐殖酸的化学性质表现为分子量增加且芳香性提高。ICP-OES分析结果表明，酸处理和水热处理相结合的方法使腐殖酸中的重金属元素显著减少。FTIR分析证实了该结果，并表明从硝酸预处理和水热生成的褐煤PHA中提取的HA富含羧基和酚羟基官能团。PHA被用作生物炭吸附重金属离子的活化剂。实验结果表明，PHA成功负载到生物炭上并引入了大量官能团，改性生物炭对Pb的吸附能力得到有效提高。
