Kunfu Pi
China University of Geosciences
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Featured researches published by Kunfu Pi.
Journal of Hazardous Materials | 2015
Kunfu Pi; Yanxin Wang; Xianjun Xie; Chunli Su; Teng Ma; Junxia Li; Yaqing Liu
Abnormal levels of co-occurring arsenic (As), fluorine (F) and iodine (I) in groundwater at Datong Basin, northern China are geochemically unique. Hydrochemical, (18)O and (2)H characteristics of groundwater were analyzed to elucidate their mobilization processes. Aqueous As, F and I ranged from 5.6 to 2680 μg/L, 0.40 to 3.32 mg/L and 10.1 to 186 μg/L, respectively. High As, F and I groundwater was characterized by moderately alkaline, high HCO3(-), Fe(II), HS(-) and DOC concentrations with H3AsO3, F(-) and I(-) as the dominant species. The plots of δ(18)O values and Cl/Br ratios versus Cl(-) concentration demonstrate build-up of more oxidizing conditions and precipitation of carbonate minerals induced by vertical recharge and intensive evaporation facilitate As retention to Fe (hydr) oxides, but enhance F and I mobilization from host minerals. Under reducing conditions, As and I can be simultaneously released via reductive dissolution of Fe (hydr) oxides and reduction of As(V) and I(V) while F migration may be retarded due to effects of dissolution-precipitation equilibria between carbonate minerals and fluorite. With the prevalence of sulfate-reducing condition and lowering of HCO3(-) concentration, As and I may be sequestered by Fe(II) sulfides and F is retained to fluorite and on clay mineral surfaces.
Science of The Total Environment | 2015
Xianjun Xie; Yanxin Wang; Kunfu Pi; Chongxuan Liu; Junxia Li; Yaqing Liu; Zhiqiang Wang; Mengyu Duan
In situ arsenic removal from groundwater by an aquifer iron coating method has great potential to be a cost effective and simple groundwater remediation technology, especially in rural and remote areas where groundwater is used as the main water source for drinking. The in situ arsenic removal technology was first optimized by simulating arsenic removal in various quartz sand columns under anoxic conditions. The effectiveness was then evaluated in an actual high-arsenic groundwater environment. The arsenic removal mechanism by the coated iron oxide/hydroxide was investigated under different conditions using scanning electron microscopy (SEM)/X-ray absorption spectroscopy, electron probe microanalysis, and Fourier transformation infrared spectroscopy. Aquifer iron coating method was developed via a 4-step alternating injection of oxidant, iron salt and oxygen-free water. A continuous injection of 5.0 mmol/L FeSO4 and 2.5 mmol/L NaClO for 96 h can form a uniform goethite coating on the surface of quartz sand without causing clogging. At a flow rate of 7.2 mL/min of the injection reagents, arsenic (as Na2HAsO4) and tracer fluorescein sodium to pass through the iron-coated quartz sand column were approximately at 126 and 7 column pore volumes, respectively. The retardation factor of arsenic was 23.0, and the adsorption capacity was 0.11 mol As per mol Fe. In situ arsenic removal from groundwater in an aquifer was achieved by simultaneous injections of As(V) and Fe(II) reagents. Arsenic fixation resulted from a process of adsorption/co-precipitation with fine goethite particles by way of bidentate binuclear complexes. Therefore, the study results indicate that the high arsenic removal efficiency of the in situ aquifer iron coating technology likely resulted from the expanded specific surface area of the small goethite particles, which enhanced arsenic sorption capability and/or from co-precipitation of arsenic on the surface of goethite particles.
Journal of Hazardous Materials | 2016
Xianjun Xie; Kunfu Pi; Yaqing Liu; Chongxuan Liu; Junxia Li; Yapeng Zhu; Chunli Su; Teng Ma; Yanxin Wang
An aquifer Fe-coating technology was evaluated for in-situ As remediation. The groundwater in the aimed aquifer has low dissolved Fe(II) concentration and high As(III) concentration, which has a low affinity toward Fe-oxides/hydroxides. To overcome these challenges, dissolved Fe(II) (5.0 mM) and NaClO (2.6 mM) were injected into the studied aquifer to promote the formation of Fe oxides/hydroxides and to oxidize As(III) into As(V), thus removing aqueous As via adsorption and/or co-precipitation. During field experiment, As concentration in groundwater from the pumping well significantly decreased. Fe and As speciation calculations indicate that incorporation of negatively charged As(V) into goethite was the probable mechanism for As removal. Both chemical sequential extraction results and spectroscopic data also support that alternating injection of Fe(II) and NaClO can achieve aquifer Fe coating and immobilize As via adsorption onto Fe oxides/hydroxides. Geochemical modelling further confirms that although competition for sorption sites between As and other dissolved species is expected in the natural groundwater system, high surface area of the Fe oxides/hydroxides can provide sufficient sites for As retention. The ability to effectively decrease As concentration of in-situ aquifer Fe-coating technology indicates that this approach should have extensive applicability to similar high As groundwater occurred worldwide.
Applied Geochemistry | 2017
Kunfu Pi; Yanxin Wang; Xianjun Xie; Teng Ma; Chunli Su; Yaqing Liu
Journal of Geochemical Exploration | 2015
Kunfu Pi; Yanxin Wang; Xianjun Xie; Shuangbing Huang; Qian Yu; Mei Yu
Water Research | 2017
Kunfu Pi; Yanxin Wang; Xianjun Xie; Teng Ma; Yaqing Liu; Chunli Su; Yapeng Zhu; Zhiqiang Wang
Journal of Geochemical Exploration | 2015
Qian Yu; Yanxin Wang; Xianjun Xie; Matthew Currell; Kunfu Pi; Mei Yu
Journal of Hydrology | 2016
Xianjun Xie; Yaqing Liu; Kunfu Pi; Chongxuan Liu; Junxia Li; Mengyu Duan; Yanxin Wang
Journal of Geochemical Exploration | 2016
Kunfu Pi; Yanxin Wang; Xianjun Xie; Yaqing Liu; Teng Ma; Chunli Su
Environmental Science: Processes & Impacts | 2016
Harold Wilson Tumwitike Mapoma; Xianjun Xie; Kunfu Pi; Yaqing Liu; Yapeng Zhu