Browsing by Author "Mortimer, Robert J. G."

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    Efficient arsenic removal by a bifunctional heterogeneous catalyst through simultaneous hydrogen peroxide (H2O2) catalytic oxidation and adsorption
    (Elsevier, 2021-10-09) Su, Jing; Lyu, Tao; Cooper, Mick; Mortimer, Robert J. G.; Pan, Gang
    Arsenic (As) is a toxic contaminant in surface waters and groundwater. Oxidation of arsenite (As(III)) to less toxic arsenate (As(V)) by hydrogen peroxide (H2O2) is desirable for enhancing the immobilisation of Arsenic (As). However, this As(III) oxidation process is constrained by the strong pH dependence and the generated As(V) must also be removed for complete As remediation. This study developed and evaluated a novel heterogeneous catalytic system using manganese-doped Lanthanum oxycarbonate (MnL) to catalyse the oxidation of As(III) by H2O2 and simultaneously adsorb the generated As(V). The presence of MnL enhanced the removal rate of As(III) by 35 times compared with systems utilising H2O2 alone. Additionally, this superior performance was observed over a wide pH range (5–9), which demonstrated this approach could bypass the well-known pH restriction on oxidation by H2O2. Mechanistic studies revealed that the long-lived superoxide radicals (·O2−/·OOH), present on the particle surfaces and derived from the dissociation of the Lewis acid-base adduct (La–OOH*), were the dominant active species for As(III) oxidation. Mn atoms with low valence states played a crucial role in As(III) oxidation through the provision of extra active sites to facilitate radical production. The La and Mn sites in MnL could rapidly immobilize the generated As(V) by forming precipitates, resulting in a final As removal efficiency of 99% even after three cycles of reutilisation. Overall, this study demonstrates the viability of the proposed novel multi-functional catalyst for efficient As remediation from aqueous environments.
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    Hydrothermal carbonization of microalgae for phosphorus recycling from wastewater to crop-soil systems as slow-release fertilizers
    (Elsevier, 2020-10-12) Chu, Qingnan; Lyu, Tao; Xue, Lihong; Yang, Linzhang; Feng, Yanfang; Sha, Zhimin; Yue, Bin; Mortimer, Robert J. G.; Cooper, Mick; Pan, Gang
    Due to the finite stocks of phosphate rock and low phosphorus (P) use efficiency (PUE) of traditional mineral P fertilizers, more sustainable alternatives are desirable. One possibility is to culture microalgae in wastewater to recover the P and then convert the microalgae biomass into slow-release fertilizers through hydrothermal carbonization (HTC). Therefore, this study aimed to recycle P from wastewater to agricultural field using microalgae and HTC technology. Chlorella vulgaris (CV) and Microcystis sp. (MS) were cultured in poultry farm wastewater with an initial concentration of 41.3 mg P kg-1. MS removed 88.4% P from the wastewater, which was superior to CV. CV- and MS-derived hydrochars were produced at 200 or 260°C, in solutions using deionized water or 1wt% citric acid. The MS-derived hydrochar using 1 wt% citric acid solution at 260 °C (MSHCA260) recovered the highest amount of P (91.5%) after HTC. The charring promoted the transformation of soluble and exchangeable P into moderately available P (Fe/Al-bound P), and using citric acid solution as feedwater increased the P recovery rate and formation of Fe/Al-bound P. With the abundant moderately available P pool, hydrochar amendment released P more slowly and enhanced the soil P availability more persistently than chemical fertilizer did, which helped to improve PUE. In a wheat-cultivation pot experiment, MSHCA260 treatment improved wheat PUE by 34.4% and yield by 21.6% more than chemical fertilizer did. These results provide a novel sustainable strategy for recycling P from wastewater to crop-soil systems, substituting the mineral P fertilizer, and improving plant PUE.
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    Nanobubble aeration enhanced wastewater treatment and bioenergy generation in constructed wetlands coupled with microbial fuel cells
    (Elsevier, 2023-06-29) Lyu, Tao; Wu, Yuncheng; Zhang, Yang; Fan, Wei; Wu, Shubiao; Mortimer, Robert J. G.; Pan, Gang
    Artificial aeration is a widely used approach in wastewater treatment to enhance the removal of pollutants, however, traditional aeration techniques have been challenging due to the low oxygen transfer rate (OTR). Nanobubble aeration has emerged as a promising technology that utilise nano-scale bubbles to achieve higher OTRs owing to their large surface area and unique properties such as longevity and reactive oxygen species generation. This study, for the first time, investigated the feasibility of coupling nanobubble technology with constructed wetlands (CWs) for treating livestock wastewater. The results demonstrated that nanobubble-aerated CWs achieved significantly higher removal efficiencies of total organic carbon (TOC) and ammonia (NH4+-N), at 49 % and 65 %, respectively, compared to traditional aeration treatment (36 % and 48 %) and the control group (27 % and 22 %). The enhanced performance of the nanobubble-aerated CWs can be attributed to the nearly three times higher amount of nanobubbles (Ø < 1 μm) generated from the nanobubble pump (3.68 × 108 particles/mL) compared to the normal aeration pump. Moreover, the microbial fuel cells (MFCs) embedded in the nanobubble-aerated CWs harvested 5.5 times higher electricity energy (29 mW/m2) compared to the other groups. The results suggested that nanobubble technology has the potential to trigger the innovation of CWs by enhancing their capacity for water treatment and energy recovery. Further research needs are proposed to optimise the generation of nanobubbles, allowing them to be effectively coupled with different technologies for engineering implementation.
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    Utilization of coal fly ash waste for effective recapture of phosphorus from waters
    (Elsevier, 2021-10-01) Xu, Rui; Lyu, Tao; Wang, Lijing; Yuan, Yuting; Zhang, Meiyi; Cooper, Mick; Mortimer, Robert J. G.; Yang, Queping; Pan, Gang
    Reutilization of the waste by-products from industrial and agricultural activities is crucially important towards attainment of environmental sustainability and the ‘circular economy’. In this study, we have developed and evaluated a sustainably-sourced adsorbent from coal fly ash, which was modified by a small amount of lanthanum (La-FA), for the recapture of phosphorous (P) from both synthetic and real natural waters. The prepared La-FA adsorbent possessed typical characteristic diffraction peaks similar to zeolite type Na–P1, and the BET surface area of La-FA was measured to be 10.9 times higher than that of the original FA. Investigation of P adsorption capability indicated that the maximum adsorption (10.8 mg P g−1) was 6.14 times higher than that (1.8 mg P g−1) of the original fly ash material. The ζ potentials measurement and P K-edge X-ray Absorption Near Edge Structure (XANES) spectra demonstrated that P was bonded on La-FA surfaces via an adsorption mechanism. After applying the proposed adsorbent to real lake water with La/P molar ratios in the range from 0.5:1 to 3:1, the La-FA adsorbent showed the highest phosphate removal ability with a La/P molar ratio 1:1, and the P adsorption was similar to that performance with the synthetic solution. Moreover, the La-FA absorbent produced a negligible effect on the concentrations of total dissolved nitrogen (TDN), NH4+-N and NO3−-N in water. This study thus provides a potential material for effective P recapture and details of its operation.