Tang Jinping, Liu Peng, Shang Jing, Fei Yingxiang
School of Environmental Studies, China University of Geosciences, Wuhan, 430074, PR China; Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot, 7610001, Israel.
School of Environmental Studies, China University of Geosciences, Wuhan, 430074, PR China; Hubei Key Laboratory of Yangtze Catchment Environmental, Aquatic Science, PR China University of Geosciences, Wuhan, 430074, PR China.
Environ Res. 2023 Nov 15;237(Pt 2):117012. doi: 10.1016/j.envres.2023.117012. Epub 2023 Sep 1.
Coal fly ash accumulation, global warming, and heavy metal-contaminated water environments are three primary environmental concerns. Porous geopolymers are economical porous adsorbents that can be produced using coal fly ash as a raw material and employed for heavy metal removal from water. However, residual alkalis on the geopolymer can lead to extreme increases in pH and cause environmental stresses, which limits the large-scale production and application of geopolymers in industries and environments. A green approach to alleviating the high basicity of geopolymers through CO exposure is proposed, with CO adsorption experiments as well as Zn removal batch and column experiments conducted to evaluate the practicality of the synergistic strategy. CO adsorption experiments show the CO capture capacity of fresh geopolymer (F@PG) is 0.80 mmol g, greater than that of the conventionally washed geopolymer (W@PG, 0.26 mmol g), with the pH of the geopolymer decreasing after both washing and CO exposure. Batch experiments suggest neither washing nor CO exposure cause a significant change in the Zn adsorption capacity of the geopolymer; column experiments show the CO-exposed geopolymer (C@PG) has a pH < 9.5 and a satisfactory Zn removal performance similar to W@PG, but F@PG with a pH ∼12 results in a conversion of Zn to anionic forms and a decrease in Zn removal efficiency. These results indicate CO exposure is a practical method to decrease the pH of geopolymers for applications related to heavy metal-contaminated water treatment and provide a large-scale industrial option for coal fly ash consumption and CO emission reduction.
粉煤灰堆积、全球变暖和重金属污染的水环境是三个主要的环境问题。多孔地质聚合物是一种经济的多孔吸附剂，它可以以粉煤灰为原料生产，并用于从水中去除重金属。然而，地质聚合物上的残留碱会导致pH值急剧升高并造成环境压力，这限制了地质聚合物在工业和环境中的大规模生产和应用。本文提出了一种通过CO暴露来缓解地质聚合物高碱度的绿色方法，并进行了CO吸附实验以及Zn去除的批次和柱实验，以评估这种协同策略的实用性。CO吸附实验表明，新鲜地质聚合物（F@PG）的CO捕获能力为0.80 mmol g，大于传统洗涤后的地质聚合物（W@PG，0.26 mmol g），洗涤和CO暴露后地质聚合物的pH值均降低。批次实验表明，洗涤和CO暴露均不会导致地质聚合物对Zn的吸附能力发生显著变化；柱实验表明，经CO暴露的地质聚合物（C@PG）的pH值<9.5，具有与W@PG相似的令人满意的Zn去除性能，但pH值约为12的F@PG会导致Zn转化为阴离子形式并降低Zn去除效率。这些结果表明，CO暴露是一种降低地质聚合物pH值的实用方法，可用于与重金属污染水处理相关的应用，并为粉煤灰消耗和CO减排提供了一种大规模工业选择。
