Metal Retention Experiments for the Design of Soil-Mix Technology Permeable Reactive Barriers

Soil-mix technology is effective for the construction of permeable reactive barriers (PRBs) for in situ groundwater treatment. The objective of this study was to perform initial experiments for the design of soil-mix technology PRBs according to (i) sorption isotherm, (ii) reaction kinetics and (iii) mass balance of the contaminants. The four tested reactive systems were: (i) a granular zeolite (clinoptilolite-GZ), (ii) a granular organoclay (GO), (iii) a 1:1-mixture GZ and model sandy clayey soil and (iv) a 1:1:1-mixture of GZ, GO and model soil. The laboratory experiments consisted of batch tests (volume 900mL and sorbent mass 18g) with a multimetal solution of Pb, Cu, Zn, Cd and Ni. For the adsorption experiment, the initial concentrations ranged from 0.01 to 0.5mM (2.5 to 30mg/L). The maximum metal retention was measured in a batch test (300mg/L for each metal, volume 900mL, sorbent mass 90-4.5g). The reactive material efficiency order was found to be GZ>GZ-soil mix>GZ-soil-GO mix>GO. Langmuir isotherms modelled the adsorption, even in presence of a mixed cations solution. Adsorption was energetically favourable and spontaneous in all cases. Metals were removed according to the second order reaction kinetics; GZ and the 1:1-mix were very similar. The maximum retention capacity was 0.1-0.2mmol/g for Pb in the presence of clinoptilolite; for Cu, Zn, Cd and Ni, it was below 0.05mmol/g for the four reactive systems. Mixing granular zeolite, organoclay and model soil increased the chemisorption. Providing that GZ is reactive enough for the specific conditions, GZ can be mixed to obtain the required sorption. Granular clinoptilolite addition to soil is recommended for PRBs for metal contaminated groundwater. The laboratory experiments consisted of batch tests with a multimetal solution of Pb, Cu, Zn, Cd and Ni. The four reactive materials chosen were granular zeolite, clinoptilolite and model sandy clayey soil, granular organoclay and a mix of clinoptilolite, model soil and organoclay. The reactive material efficiency order was found to be granular clinoptilolite>clinoptilolite-soil mix>clinoptilolite-soil-organoclay mix>granular organoclay. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparison between granular pillared, organo- and inorgano-organo-bentonites for hydrocarbon and metal ion adsorption

Granular reactive materials have higher permeability and are therefore desirable for in situ groundwater pollution control. Three granular bentonites were prepared: an Al-pillared bentonite (PBg), an organo-bentonite (OBg) using a quaternary ammonium cation (QAC), and an inorgano-organo-bentonite (IOBg), using both the pillaring agent and the QAC. Powdered IOB (IOBp) was also prepared to test the effect of particle size. The modified bentonites were characterised with X-ray diffraction (XRD), Fourier transform infrared spectrometry (FT-IR), thermal gravimetric analysis (TGA) and uniaxial compression tests. The d-spacing increased only with QAC intercalation. The Young's modulus of IOBg was twice as high as OBg. Batch adsorption tests were performed with aqueous multimetal solutions of Pb2+, Cu2+, Cd2+, Zn2+ and Ni2+ ions, with liquid dodecane and with aqueous dodecane solutions. Metal adsorption fit the Langmuir isotherm. Adsorption occurred within 30min for PBg, while the granular organo-bentonite needed at least 12h to reach equilibrium. IOBp had the maximum adsorption capacity at higher metal concentration and lower adsorbent content (Cu2+: 2.2, Ni2+: 1.7, Zn2+: 1.4, Cd2+: 0.9 and Pb2+: 0.7 all in mmolg-1). The dual pillaring of the QAC and Al hydroxide increased the adsorption. The adsorption of liquid dodecane was in the order IOBg>OBg>PBg (3.2>2.7>1.7mmolg-1). Therefore IOBg has potential for the removal of toxic compounds found in soil, groundwater, storm water and wastewater. © 2012 Elsevier B.V.

A comprehensive study of lysozyme adsorption using dual polarization interferometry and quartz crystal microbalance with dissipation.

Protein adsorption plays a crucial role in biomaterial surface science as it is directly linked to the biocompatibility of artificial biomaterial devices. Here, elucidation of protein adsorption mechanism is effected using dual polarization interferometry and a quartz crystal microbalance to characterize lysozyme layer properties on a silica surface at different coverage values. Lysozyme is observed to adsorb from sparse monolayer to multilayer coverage. At low coverage an irreversibly adsorbed layer is formed with slight deformation consistent with side-on orientation. At higher coverage values dynamic re-orientation effects are observed which lead to monolayer surface coverages of 2-3 ng/mm² corresponding to edge-on or/and end-on orientations. These monolayer thickness values ranged between 3 and 4.5 nm with a protein density value of 0.60 g/mL and with 50 wt% solvent mass. Further increase of coverage results formation of a multilayer structure. Using the hydration content and other physical layer properties a tentative model lysozyme adsorption is proposed.

A comprehensive study of lysozyme adsorption using dual polarization interferometry and quartz crystal microbalance with dissipation

Protein adsorption plays a crucial role in biomaterial surface science as it is directly linked to the biocompatibility of artificial biomaterial devices. Here, elucidation of protein adsorption mechanism is effected using dual polarization interferometry and a quartz crystal microbalance to characterize lysozyme layer properties on a silica surface at different coverage values. Lysozyme is observed to adsorb from sparse monolayer to multilayer coverage. At low coverage an irreversibly adsorbed layer is formed with slight deformation consistent with side-on orientation. At higher coverage values dynamic re-orientation effects are observed which lead to monolayer surface coverages of 2-3 ng/mm2 corresponding to edge-on or/and end-on orientations. These monolayer thickness values ranged between 3 and 4.5 nm with a protein density value of 0.60 g/mL and with 50 wt% solvent mass. Further increase of coverage results formation of a multilayer structure. Using the hydration content and other physical layer properties a tentative model lysozyme adsorption is proposed. © 2012 Elsevier Ltd.