Zhenghui Zhao

Evaluation of nitrate and phosphate adsorption on Al-modified biochar: Influence of Al content

Biochars with different Al contents (i.e., 5, 10, 15, and 20 wt%) were prepared to evaluate their adsorption capacities for nitrate (NO3-) and phosphate (PO43-) from eutrophic water. Several techniques, including N2 adsorption-desorption, X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectrometry, were applied to characterize the physical-chemical properties of the biochars. We found that the NO3- and PO43- adsorptions significantly improved on the Al-modified biochars because of their multifunctional and surface charge properties. In single-solute adsorption, 15 Al/BC and 20 Al/BC exhibited optimal NO3- and PO43- adsorption capacities, respectively. In bi-solute coadsorption, the PO43- adsorption on the biochar was less affected with the coexistence of NO3-, whereas the coexistence of PO43- had a significant impact on the NO3- adsorption. The optimal solution pH for NO3- adsorption was 6, and pH < 6 was advantageous to PO43- adsorption. In the kinetic study, the pseudo-second-order model could describe the NO3- and PO43- adsorptions on biochar well, indicating that chemical adsorption was the main adsorption mechanism. The Langmuir-Freundlich model agreed well with the NO3- and PO43- adsorptions on the biochars, and the maximum adsorption capacities for NO3- and PO43- reached 89.58 mg/g and 57.49 mg/g, respectively. Therefore, the Al-modified biochar was a good choice for the remediation of eutrophic water.

Biochar as an adsorbent for inorganic nitrogen and phosphorus removal from water: a review

Biochar is the solid product of biomass pyrolysis that can be used for carbon sequestration, soil amendment, and pollution remediation. The use of biochar as an adsorbent for the removal of water contaminants has elicited increasing interest due to the multifunctional properties of this material. The application of biochar in the adsorption of inorganic nutrients from eutrophic water has not been reviewed. This review focuses on recent research on the use of biochar for the adsorption of inorganic nitrogen (ammonium and nitrate) and phosphorus (phosphate) from water, especially for the main influence factors and mechanisms for nitrogen and phosphorus adsorption on biochar.

Preparing coal slurry from coking wastewater to achieve resource utilization: Slurrying mechanism of coking wastewater–coal slurry

Coking wastewater is used to prepare coal slurry, which can be used as combustion and gasification fuel. This promising technology simultaneously achieves resource utilization and wastewater management. Slurrying properties are essential to the industrial application of coal slurry. These properties are considerably influenced by coal surface properties and the adsorption of an additive by coal. In this study, the effects of the internal components (e.g., phenol, ammonia nitrogen, and metal ions) of coking wastewater on the adsorption of an additive by coal and on coal surface properties were measured. Results showed that the competitive adsorption between phenol and the additive reduced the amount of additive adsorbed on coal. However, phenol acted as an additive to improve the wettability of coal particles. Cations (Ca2+, NH4+, and Na+) adversely affected the slurrying because they weakened the negative charges of coal. Furthermore, a large amount of water was adsorbed due to the ionic bonding effects, thereby reducing the free water in the coal slurry system. The maximum slurrying concentration of CWCS was 0.8 percentage points higher than that of CWS, suggesting that coking wastewater enhanced the slurrying capability of the coal slurry by integrating the various effects induced by the different internal components.