| Groundwater is an important part of water resources, and is an importantresource in dealing with the issue of water scarcity in industry, agriculture, domesticwater in our country. Groundwater is characteristic of wide distribution, stable waterquantity, and better water quality. In recent decades, the growing economy made thehuman exploitation of natural resources increasingly, so that the groundwater sufferedvarying degrees of contamination. High stability, hard degradable properties of heavymetal make heavy metals in groundwater suffer unpredictable dangers. As a typicalheavy metal pollutant, lead is one of the famous "top five", which has teratogenic,carcinogenic, mutagenic features. With the increasing incidence of lead pollution,lead-contaminated groundwater remediation research is imperative.Over the last decade, a great deal of research has been focused on the removal ofcontaminants by zero-valent iron(ZVI), because ZVI is abundant, easy to produce,reactive with different kinds of contaminants. Nano-scale zero valent iron(NZVI),with the characters of small particle size, large specific surface area and surfaceenergy, has higher reactivity, stronger reducibility and adsorption with the samechemical property of ZVI.However, due to the lack of dispersibility and inoxidizability, its application inremediation of contaminated groundwater is limited, which made necessary to modify.For this reason, modification is needed to improve its properity in remedinggroundwater.This paper discussed the feasibility for lead-contaminated groundwaterremediation with resin-modified NZVI, and constracted the reactor with organic glasscolumn to study the remediation effect of dynamic conditions on the basis of batchexperiments. The concrete research content and results are as follows:(1) The shape, main ingredients and stability of experimental modified-NZVIwere characterized by SEM and XRD. The results suggested that the particlesarranged to flocculent structure, with size ranged from50to200nm. The particles, mainly composed of Fe(0), were stable for more than60days with stronger stabilityand inoxidizability.(2) Remediation effect of resin-modified NZVI for Pb polluted groundwater wasstudied, and basic reaction parameters, kinetics and mechanism was determined. Theresults indicated the reduction of Pb could be described by pseudo-first-order kineticmodel, and the mechanism was combined effect of adsorption and reduction. Theremoval rate of Pb using resin-modified NZVI was affected by many factors. Theremoval rate increased as the increase of resin-modified NZVI and the decrease ofcontaminant initial concentration. DO, as the electron acceptor, can react with Fe(0)against Pb2+, so it’s beneficial for contaminant reduction in groundwater withoutoxygen. The initial pH had slight influence for the removal effect of Pb, which theoptimum pH in4in this experiment.(3) The reduction of Pb by resin-modified NZVI followed a pseudo-first-orderkinetic model despite of the exist of different ions in groundwater, however Kobswasrelated to the species and concentrations of ions. SO42-and Cl-could promote theremoval of Pb by destructibility of surface passivation or the formation of green rust.HCO3-and Pb2+generated sediment of PbCO3when HCO3-excited, and significantlyreduce the concentration of contaminant at a preliminary stage, and the pH buffing ofHCO3-also accelerated the reactive process; Ca2+and Mg2+would easily formprecipitationand restrain the reactive process with OH-in the groundwater, and Ca2+issronger than Mg2+with inhibiting effect.(4) Organic glass column test on the basis of batch experiments was constructedto simulate the contaminants migration and remediation in dynamic conditions, andto discuss the influence to remediation effect by dosage of resin-modified NZVI,addition of activated carbon and flow velocity. Remediation effect can be acceleratedby increasing amount of the resin-modified NZVI; Pb removal effect can also bepromoted with increasing activated carbon, however, the concentration of total solubleiron was very high at a preliminary stage, which may cause excessive amount of ironin groundwater; The growing velocity of groundwater would weaken removal rate Pb contaminant. |
