Xicheng Wang,Shucheng Yuan,Caobin Wu,Xiao Sun,Shougang Chen,Qingguo Wang
The removal of tetracycline (TC) from wastewater was a necessity due to the overuse of antibiotics and its deleterious effects on the environment. In this study, an adsorbent for the removal of tetracycline was prepared by modifying waste concrete powder using a straightforward iron (iii) chloride (FeCl 3 ) precipitation method. The structure of the prepared material was characterized using a scanning electron microscope(SEM), a specific surface area and pore size analyzer (BET), a Fourier transform infrared spectroscopy(FTIR), an X-ray diffractometer (XRD), and an X-ray photoelectron spectroscopy (XPS). The characterization results demonstrated that amorphous iron (iii) hydroxyl oxides were successfully loaded onto concrete powder. The modified concrete powder exhibited a porous structure, with a notable increase in specific surface area from 12.8 m²/g to 111.5 m²/g and a substantial rise in pore volume from 0.052 cm³ /g to 0.107 cm³ /g. The results of the batch adsorption experiments demonstrated that the adsorbent exhibited a high removal rate of tetracycline, reaching 83.3 % at pH of 4, a dosage of 2 g/L, a temperature of 25°C, and a TC concentration of 10 mg /L. Furthermore, the effects of the initial pH of the solution, the dosage of the adsorbent, and the presence of co-existing ions on the adsorption of tetracycline from modified concrete powder were investigated. The adsorption kinetics revealed that the pseudo-second-order model was more consistent with the adsorption behavior, while the adsorption isotherms indicated that the Freundlich model was more suitable than the Langmuir model. Moreover, an examination of the thermodynamic outcomes substantiated that the adsorption was spontaneous, and endothermic. The primary mechanisms of TC removal by modified concrete powder are electrostatic attraction, hydrogen bonding interactions, pore-filling effects, and surface complexation. This study presented a convenient, effective, and potentially profitable method for the construction of adsorbents with low-cost to remove TC from wastewater.
This study investigates the environmental and mechanical implications of incorporating silica fume into lime-activated thermo-mechanically treated waste concrete powder (TMWCP) to develop a sustainable clinker-free binder. The novel activation method involves thermo-mechanical treatment of WCP, followed by lime and calcium formate chemical activation. The results demonstrated that incorporating silica fume enhanced the pozzolanic reactivity , which led to the formation of C–S–H, pore refinement, and a dramatic increase in compressive strength . For instance, the incorporation of 20 % and 25 % silica fume exhibited compressive strength of 46 MPa and 43 MPa after 28 days of curing. The developed clinker-free binder with the addition of 20 % silica fume demonstrated a reduction in mineral resource consumption of 99.3 % and CO 2 emissions of 13 % and 69.3 % compared to the sample without silica fume and ordinary Portland cement , respectively. This study offers a promising avenue for the widespread utilization of WCP as an environmentally friendly clinker-free binder.
Waste concrete, a bulk solid waste currently underutilized in industry, contains calcium resources that can be valorized via CO₂ mineralization. This study develops a scalable method to synthesize high-purity vaterite by extracting Ca²⁺ from hardened cement paste powder (HCPP) using 0.8 M NH 4 Cl for 60 minutes, followed by sodium dodecyl benzene sulfonate (SDBS)-mediated aqueous carbonation at 25°C with a CO₂ flow rate of 0.5 L/min. The factors affecting the leaching of Ca 2 + , and the content and types of calcium carbonate (CaCO 3 ) generated were investigated. Quantitative phase analysis via XRD Rietveld refinement confirmed 98.9 % vaterite purity under optimized conditions. Moreover, scanning electron microscope (SEM) analysis revealed the growth process of vaterite at varying temperatures. Specifically, at low carbonation temperature (25, 40°C), the initial formation was of shell-like vaterite, which transitioned into nano-vaterite and eventually developed into a dense internal structure. Conversely, at high carbonation temperature (60°C), leaf-like vaterite grew first and subsequently evolved into a flower-like structure.
危险品化学品经营许可证（带存储）