Zhongbo Shang,LiWen Zhang,Xuyang Zhao,Shanhu Liu,Deliang Li
A low-cost mercapto-modified coal gangue (CG-SH) was fabricated by modification of coal gangue (CG) with (3-mercaptopropyl) trimethoxysilane. The structure and composition for as-prepared CG-SH were characterized by using X-ray diffraction (XRD), Fourier transfer infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray fluorescence (XRF). Results indicated that larger amounts of mercapto-groups (-SH) was successfully introduced onto CG, which followed by acted as active sites for the removal of heavy metal cations, such as Pb(II), Cd(II) and Hg(II). The factors that affected the adsorption equilibrium as well as the removal efficiency, i.e., contact time, initial concentration, pH and temperature, were investigated in detail. The adsorption isotherms for Pb(II), Cd(II) and Hg(II) were well fitted with Langmuir model. The maximum adsorption capacity of CG-SH for Pb(II), Cd(II) and Hg(II) were calculated to be 332.8, 110.4 and 179.2 mg g −1 , respectively. The adsorption for Pb(II), Cd(II) and Hg(II) on CG-SH could be well described by pseudo-second-order kinetic model . And thermodynamic analysis suggests that the adsorption process for Pb(II) is exothermal, while that for Cd(II) and Hg(II) are endothermal. The results suggest CG-SH have great potential to be used as efficient absorbent for the removal of heavy metal cations from water.
Soil cadmium (Cd) contamination has emerged as a critical environmental challenge in Chinese agricultural systems. The remediation of Cd-contaminated farmland necessitates high-efficient immobilization amendments. The present study successfully synthesized mercapto-modified MgAl- and ZnAl-layered double hydroxides (MgAl/ZnAl-MP-LDHs) as structurally stable and high-performance amendments via a coprecipitation-condensation method. Batch adsorption experiments revealed superior Cd 2+ sorption capacities for MP-LDHs, with the maximum Cd 2+ capacities increased by 1.6–1.8 times compared to the unmodified materials. The XPS analysis further elucidated the dual sorption mechanisms involve in Cd 2+ absorption by MP-LDHs: complexation via mercapto groups and precipitation mediated by hydroxyl groups. Moreover, soil application of MP-LDHs at 0.025% dosage (w/w) demonstrated rapid immobilization efficacy, reducing available Cd content by 38.41%–93.20% within 24 h in alkaline and acidic soil. Subsequent analysis revealed that MP-LDHs exhibited pH-resilient performance in soil Cd immobilization. Potting experiment further validated practical applicability of MP-LDHs, reducing pakchoi shoot Cd concentration by 53.52%–95.24% at 0.025%–0.1% dosage. The findings established MP-LDHs as multifunctional amendments with ultralow application dosage requirements, excellent immobilization efficiency, and universal performance across varying soil pH levels, hence positioning MP-LDHs as a scalable solution for safe utilization of Cd-contaminated soil.
This study delves into the impact of the hydrolysis/condensation of 3-mercaptopropyltrimethoxysilane (MPTMS) on the modification of thiol groups on the surface of silica particles. By employing an optimized Stöber method, such as the pH, water content, and quantity of MPTMS in the reaction system, a systematic exploration of the size, shape, and size/shape distribution of the thiol-modified silica particles was carried out. During these investigations, Ellman’s colorimetric method and Raman spectroscopy were utilized to quantitatively analyze the changes in the amount of thiol modification on the surface of silica particles. Furthermore, the synthesized SH-SiO2 particles were employed as adsorption carriers for Au3+ ions, which were then reduced to form SH-SiO2/Au composite particles. Significantly, these prepared SH-SiO2/Au composite particles exhibited remarkable catalytic activity in the reduction reaction of p-nitroaniline.
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