Lianghu Su

Copper leaching of MSWI bottom ash co-disposed with refuse: Effect of short-term accelerated weathering

Co-disposal of refuse with municipal solid waste incinerator (MSWI) bottom ash (IBA) either multi-layered as landfill cover or mixed with refuse could pose additional risk to the environment because of enhanced leaching of heavy metals, especially Cu. This study applied short-term accelerated weathering to IBA, and monitored the mineralogical and chemical properties of IBA during the weathering process. Cu extractability of the weathered IBA was then evaluated using standard leaching protocols (i.e. SPLP and TCLP) and co-disposal leaching procedure. The results showed that weathering had little or no beneficial effect on Cu leaching in SPLP and TCLP, which can be explained by the adsorption and complexation of Cu with DOM. However, the Cu leaching of weathered IBA was reduced significantly when situated in fresh simulated landfill leachate. This was attributed to weakening Cu complexation with fulvic acid or hydrophilic fractions and/or intensifying Cu absorption to neoformed hydr(oxide) minerals in weathered IBA. The amount of total leaching Cu and Cu in free or labile complex fraction (the fraction with the highest mobility and bio-toxicity) of the 408-h weathered IBA were remarkably decreased by 86.3% and 97.6% in the 15-day co-disposal leaching test. Accelerated weathering of IBA may be an effective pretreatment method to decrease Cu leaching prior to its co-disposal with refuse.

Performance evaluation of zero-valent iron nanoparticles (NZVI) for high-concentration H2S removal from biogas at different temperatures

The removal performance of high-concentration H2S (ca. 10 000 ppm) from simulated biogas by zero-valent iron nanoparticles (NZVI), with the majority of the particles in the size range of 60–150 nm, at different reaction temperatures (room temperature, 100 °C, 200 °C and 250 °C) were evaluated using a custom-designed quartz fixed-bed reactor. The results showed that the H2S removal capacities of NZVI were quite limited at room temperature and 100 °C, being 12.56 and 14.77 mg H2S gNZVI−1, respectively. However, these values increased significantly to 391.02 (200 °C) and 488.95 (250 °C) mg H2S gNZVI−1. Scanning electron microscopy analysis showed that the products of the NZVI–H2S reaction aggregated to form irregular polygonal-shaped structures. The main X-ray diffraction pattern peaks of the product matched well with troilite, and no pyrite was observed. The deconvolution of the X-ray photoelectron spectrometry peaks showed the presence of monosulphide (S2−) and disulphide (S22−) in the product, in which 36% of the sulphur existed as monosulphide and 64% as disulphide. It is proposed that the effective removal of hydrogen sulphide by NZVI at elevated temperatures can be attributed to the combination of nano-constituents, oxide shell and underlying Fe core to produce FeS similar to troilite and amorphous FeS2.

Efficient capture of aqueous humic acid using a functionalized stereoscopic porous activated carbon based on poly(acrylic acid)/food-waste hydrogel

Stereoscopic porous carbons have shown good potential in humic acid (HA) removal. In this work, a novel stereoscopic porous activated carbon (SPAC) was designed and synthesized via the self-assembly of a hydrogel based on food waste during in-situ polymerization, vacuum drying, carbonization, and activation. Then, the SPAC was functionalized with 3-aminopropyltriethoxysilane (APTES) and the adsorption behavior of the modified SPAC (SPAC-NH2) was studied systematically. The effects of pH, contact time, initial concentration of HA, and adsorbent dose were investigated, showing that optimal HA removal efficiency (>98.0%) could be achieved at an initial HA concentration of 100 mg/L. The experimental adsorption isotherm data was fitted to the Langmuir model with a maximum adsorption capacity of 156.0 mg HA/g SPAC-NH2. Analysis of the mechanism indicated that the removal of HA was mainly realized through the amidization reaction between the COOH groups of HA and the NH2 groups of APTES. All of the above results showed that SPAC-NH2 powder is an efficient, eco-friendly, and reusable adsorbent which is suitable for the removal of HA from wastewater.