The properties and curing mechanism of leaded samples solidified with phosphorous-slag-based cementitious pastes are studied. The compressive strength, pH of percolate, and lead-ion concentrations of leaded samples stabilized with the phosphorous-slag-based cementitious pastes and cement were analyzed. Results confirmed that the phosphorous-slag-based cementitious paste performed much better than cement in terms of solidifying lead. The cured form of lead with phosphorous-slag-based cementitious pastes had higher compressive strength, lower lead leaching, and smaller change in pH. Higher lead content corresponded with more obvious advantagees of phosphorus-slag-based cementitious pastes and lower risk of environmental pollution. By means of X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Energy Dispersive Spectrometer-Scanning Electron Microscope (EDS-SEM) analyses, we found that the hydration of phosphorus-slag-based cementitious pastes produced hydrated calcium silicate gels, ettringite and other minerals with large specific surface areas, as well as some leaded products that can combine with lead ions to form chemically stable leaded products. This finding well explained the high performance of phosphorus-slag-based cementitious pastes in terms of lead solidification and stabilization.
In this paper, the biochar prepared by pyrolysis biomass of Water Hyacinth were used as adsorption materials. The effects of initial concentration, adsorption temperature and electrolyte concentration on the adsorption process were analyzed. The adsorption effect of biochar prepared from the stem and root parts of biomass on Cd 2+ in solution was investigated, and the interaction between leaching rule of alkali (earth) metal K + , Mg 2+ , Ca 2+ and adsorption of heavy metal ions in the process of adsorption was studied. The results showed that the biochar prepared by pyrolysis of stem biomass (SBC) has a richer pore structure. Compared with the biochar prepared by root biomass (RBC), the specific surface area and pore volume of SBC increased by 25.85% and 27.91% respectively. This phenomenon indicated that SBC had a stronger adsorption effect than RBC. At 25ºC, the maximum adsorption capacity of RBC and SBC for Cd 2+ was 77.20 mg g -1 and 87.20 mg g -1 , respectively. Isothermal adsorption experiments and ionic strength experiments showed that the increase of temperature could promote the adsorption of Cd 2+ by biochar. The adsorption process has a high degree of fitting with the Langmiur model, as well as the pseudo-second-order model. The adsorption sites were normally on the inner and outer surfaces of biochar, and the adsorption process was multi-molecular layer adsorption. In addition, the adsorption of Cd 2+ by biochar had a correlation with the leaching of alkali (earth) metal in the system. In the adsorption process, the leaching of alkali (earth) metals was affected by the initial concentration of Cd 2+ in the solution, and SBC leached more alkali (earth) metals than RBC, which proved that SBC has more
In this study, we prepared a novel sorbent derived from precipitating copper ion onto the surfaces of activated carbon (Cu-AC). The sorbents were comprehensively characterized by Brunauer–Emmett–Teller (BET), zeta potential analysis, SEM, XRD, and FTIR. Batch experiments were conducted to evaluate selenate removal by Cu-AC under different conditions. The results showed that Cu was uniformly coated on the AC surface. Copper pretreatment markedly decreased the specific surface area and total pore volume of AC, and changed its surface zeta potential from highly negative to low negative and even positive. The Cu-AC substantially improved selenate adsorption capacity from the 1.36 mg Se/g AC of raw AC to 3.32, 3.56, 4.23, and 4.48 mg Se/g AC after loading of 0.1, 0.5, 1.0, and 5 mmol Cu/g AC, respectively. The results of toxicity leaching test showed AC coated with ≤1.0 mmol Cu/g was acceptable for potential application. Selenate adsorption was significantly inhibited by high ionic strength (>50 mM NaCl) and pH (>10). The electrostatic attraction between positive surface charge of Cu-AC and selenate ions and hydrogen bonding between CuO and HSeO4− might contribute to selenate sorption. Evidence showed that the selenate adsorption might involve outer-sphere surface complexation. The adsorption data appeared to be better described by Langmuir than Freundlich isotherm. The spent adsorbent could be effectively regenerated by hydroxide for reuse. Only a little decrease of removal efficiency was observed in the second and third run. This study implies that Cu-coated AC is a potential adsorbent for sustainable removal selenate from relative low salinity water/wastewater.
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