Efficient removal and recovery of phosphorus from industrial wastewater in the form of vivianite.

With the shortage of phosphorus resources, the concept of phosphorus recovery from wastewater is generally proposed. Recently, phosphorus recovery from wastewater in the form of vivianite has been widely reported, which could be used as a slow-release fertilizer as well as the production of lithium iron phosphate for Li-ion batteries. In this study, chemical precipitation thermodynamic modeling was applied to evaluate the effect of solution factors on vivianite crystallization with actual phosphorus containing industrial wastewater. The modeling results showed that the solution pH influences the concentration of diverse ions, and the initial Fe2+ concentration affects the formation area of vivianite. The saturation index (SI) of vivianite increased with the initial Fe2+ concentration and Fe:P molar ratio. pH 7.0, initial Fe2+ concentration 500 mg/L and Fe:P molar ratio 1.50 were the optimal conditions for phosphorus recovery. Mineral Liberation Analyzer (MLA) accurately determined the purity of vivianite was 24.13%, indicating the feasibility of recovering vivianite from industrial wastewater. In addition, the cost analysis showed that the cost of recovering phosphorus by the vivianite process was 0.925 USD/kg P, which can produce high-value vivianite products and realize "turn waste into treasure".

Converting wastes to resource: Utilization of dewatered municipal sludge for calcium-based biochar adsorbent preparation and land application as a fertilizer.

Pyrolysis combined with land application for dewatered municipal sludge disposal revealed advantages in heavy metals solidification and resource utilization compared with other disposal technologies. In this study, utilizing dewatered municipal sludge for calcium-containing porous adsorbent preparation via pyrolysis was proposed and verified. After pyrolyzing at 900 ° C (Ca-900), the dewatered sludge obtained maximum adsorption capacity (83.95 mg P⋅ g-1) and the adsorption process conformed to the pseudo-second-order model and double layer model. Characteristic analysis showed the predominant adsorption mechanism was precipitation. Continuous column bed experiment indicated 2 g adsorbent could remove 4.27 mg phosphorus from tail wastewater with the initial phosphorus concentration of 1.03 mg ⋅ L-1. No heavy metals leaching was observed from Ca-900 adsorbent with pH value exceeding 1.0, and merely 1% addition of Ca-900 adsorbent (after actual water phosphorus adsorption) with soil could extremely promote the early growth of seedlings. Economic estimates demonstrated that this cost-effective modification could generate the most add-on value production. Based on these results, the strategy of 'one treatment but two uses' was proposed in this study, converting the wastes to resource and providing a native strategy for sludge disposal and resource recovery.

Advanced treatment of phosphorus-containing tail water by Fe-Mg-Zr layered double hydroxide beads: Performance and mechanism.

The adsorption process for low concentration phosphorus wastewater treatment has advantages of simple convenience, stable performance and less sludge, while most of current adsorbents fail to be separated for reuse. Meanwhile, few people pay attention to the removal of low concentration phosphorus from tail water by adsorbents. In this study, a newly efficient Fe-Mg-Zr layered double hydroxide beads were prepared by simple in-situ crosslinking method and applied for low concentration phosphorus adsorption from real tail water. The maximum adsorption capacity of Fe-Mg-Zr beads was 21.61 mg/g, showing more practical application value for phosphorus removal. Fixed bed experiments showed that 5.0 g adsorbent could removed 2.12 mg phosphorus from tail wastewater containing 1.03 mg/L phosphorus. The beads adsorbent can be reused with excellent adsorption performance even after five cycles of adsorption-desorption operation. After detailed analyses, it was found that ligand exchange and ion exchange were the dominant mechanisms for phosphorus adsorption by this beads. Overall, the material has the advantages of simple preparation, good adsorption performance, easy separation and recycle, indicating a great potential for low concentration phosphorus wastewater treatment.