Browsing by Author "Ajmal, Zeeshan"

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    Phosphate removal from aqueous solution using iron oxides: adsorption, desorption and regeneration characteristics
    (Journal of Colloid and Interface Science, 2018) Ajmal, Zeeshan; Muhmood, Atif; Usman, Muhammad; Kizito, Simon; Lu, Jiaxin; Dong, Renjie; Wu, Shubiao
    Dynamics of phosphate (PO4 3-) adsorption, desorption and regeneration characteristics of three lab-synthesized iron oxides, ferrihydrite (F), goethite (G), and magnetite (M) were evaluated in this study. Batch experiments were conducted to evaluate the impact of several adsorption parameters including adsorbent dosage, reaction time, temperature, pH, and ionic strength. The results showed that PO4 3- adsorption increased with reaction time and temperature while it decreased with an increase in solution pH. Adsorption isotherm data exhibited good agreement with the Freundlich and Langmuir model with maximum monolayer adsorption capacities of 66.6 mg·g-1 (F), 57.8 mg·g-1 (M), and 50.5 mg·g-1 (G). h u u Δ < ΔH > ΔS > demonstrating that PO4 3- adsorption onto tested minerals is endothermic, spontaneous, and disordered. The PO4 3- removal mostly occurred via electrostatic attraction between the sorbate and sorbent surfaces. Moreover, the PO4 3- sorption was reversible and could be desorbed at varying rates in both neutral and alkaline environments. The good desorption capacity has practical benefits for potential regeneration and re-use of the saturated particles in wastewater treatment systems.
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    Treatment of anaerobic digested effluent in biochar-packed vertical flow constructed wetland columns: Role of media and tidal operation
    (Science of the Total Environment, 2017) Kizito, Simon; Lv, Tao; Wua, Shubiao; Ajmal, Zeeshan; Luo, Hongzhen; Dong, Renjie
    Three types of vertical flow constructed wetland columns (VFCWs), packed with corn cob biochar (CB-CW), wood biochar (WB-CW) and gravel (G-CW) under tidal flowoperations, were comparatively evaluated to investigate anaerobic digested effluent treatment performance and mechanisms. Itwas demonstrated that CB-CWand WB-CWprovide significantly higher removal efficiencies for organic matter (N59%), NH4 +-N (N76%), TN (N37%) and phosphorus (N71%), compared with G-CW (22%–49%). The higher pollutants removal ability of biocharpacked VFCWs was mainly attribute to the higher adsorption ability and microbial cultivation in the porous biochar media. Moreover, increasing the flooded/drained ratio from 4/8 h to 8/4 h of the tidal operation further improved around 10% of the removal of both organics and NH4 +-N for biochar-packed VFCWs. The phosphorus removal was dependent on the media adsorption capacities through the whole experiment. However, the NH4 +-N biodegradation by microbial communities was demonstrated to become the dominant removal mechanismin the long termtreatment,which compensated the decreased adsorption capacities of the media. The study supported that the use of biochar would increase the treatment performance and elongate the lifespan of CWs under tidal operation.