Dipartimento di Ingegneria Civile e Industriale, Università di Pisa, Largo Lucio Lazzarino 1, 56122, Pisa, Italy.
Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via G. Moruzzi 13, 56124, Pisa, Italy.
J Environ Manage. 2023 Nov 1;345:118887. doi: 10.1016/j.jenvman.2023.118887. Epub 2023 Sep 5.
The management of sewage sludge is currently an open issue due to the large volume of waste to be treated and the necessity to avoid incineration or landfill disposal. Hydrothermal carbonization (HTC) has been recognized as a promising thermochemical technique to convert sewage sludge into value-added products. The hydrochar (HC) obtained can be suitable for environmental application as fuel, fertilizer, and sorbent. In this study, activated hydrochars (AHs) were prepared from sewage sludge through HTC followed by chemical activation with potassium hydroxide (KOH) and tested for the removal of pollutants in gaseous and aqueous environments, investigating carbon dioxide (CO) and ciprofloxacin (CIP) adsorption capacity. The effects of activation temperature (550-750 °C) and KOH/HC impregnation ratio (1-3) on the produced AHs morphology and adsorption capacity were studied by Response Surface Methodology (RSM). The results of RSM analysis evidenced a maximum CO uptake of 71.47 mg/g for mild activation conditions (600-650 °C and KOH/HC = 1 ÷ 2), whereas the best CIP uptake of 628.61 mg/g was reached for the most severe conditions (750 °C, KOH/HC = 3). The prepared AHs were also applied for the removal of methylene blue (MB) from aqueous solutions, and the MB uptake results were used for estimating the specific surface area of AHs. High surface areas up to 1902.49 m/g were obtained for the highest activation temperature and impregnation ratio investigated. Predictive models of CO and CIP uptake were developed by RSM analysis, and the optimum activation conditions for maximizing the adsorption performance together with high AH yield were identified: 586 °C and KOH/HC ratio = 1.34 for maximum yield (26.33 %) and CO uptake (67.31 mg/g); 715 °C and KOH/HC ratio = 1.78 for maximum yield (18.75 %) and CIP uptake (370.77 mg/g). The obtained results evidenced that chemical activation of previously HTC-treated sewage sludge is a promising way to convert waste into valuable low-cost adsorbents.
由于需要处理的废物量大，并且需要避免焚烧或填埋处理，因此目前污水污泥的管理是一个悬而未决的问题。水热碳化（HTC）已被认为是一种很有前途的热化学技术，可以将污水污泥转化为有价值的产品。所得的水热炭（HC）可作为燃料、肥料和吸附剂适用于环境应用。在这项研究中，通过 HTC 从污水污泥中制备了活性水热炭（AHs），然后用氢氧化钾（KOH）进行化学活化，并研究了它们在气态和水相环境中去除污染物的能力，考察了它们对二氧化碳（CO）和环丙沙星（CIP）的吸附能力。通过响应面法（RSM）研究了活化温度（550-750°C）和 KOH/HC 浸渍比（1-3）对所制备的 AHs 形态和吸附能力的影响。RSM 分析的结果表明，在温和的活化条件（600-650°C，KOH/HC=1/2）下，CO 的最大吸附量为 71.47mg/g，而在最苛刻的条件（750°C，KOH/HC=3）下，CIP 的最大吸附量为 628.61mg/g。所制备的 AHs 还应用于从水溶液中去除亚甲蓝（MB），并将 MB 的吸附结果用于估计 AHs 的比表面积。在所研究的最高活化温度和浸渍比下，获得了高达 1902.49m/g 的高比表面积。通过 RSM 分析，建立了 CO 和 CIP 吸附的预测模型，确定了最佳的活化条件，以最大限度地提高吸附性能和 AHs 的产率：586°C，KOH/HC 比=1.34，以获得最大产率（26.33%）和 CO 吸附（67.31mg/g）；715°C，KOH/HC 比=1.78，以获得最大产率（18.75%）和 CIP 吸附（370.77mg/g）。结果表明，对先前经过 HTC 处理的污水污泥进行化学活化是一种将废物转化为有价值的低成本吸附剂的有前途的方法。
