New synthesis method of HA/P(D,L)LA composites: study of fibronectin adsorption and their effects in osteoblastic behavior for bone tissue engineering

A novel synthetic method to synthesize hydroxyapatite/poly (D,L) lactic acid biocomposite is presented in this study by mixing only the precursors hydroxyapatite and (D,L) LA monomer without adding neither solvent nor catalyst. Three compositions were successfully synthesized with the weight ratios of 1/1, 1/3, and 3/5 (hydroxyapatite/(D,L) lactic acid), and the grafting efficiency of poly (D,L) lactic acid on hydroxyapatite surface reaches up to 84?%. Scanning electron microscopy and Fourier transform infrared spectroscopy showed that the hydroxyapatite particles were successfully incorporated into the poly (D,L) lactic acid polymer and X ray diffraction analysis showed that hydroxyapatite preserved its crystallinity after poly (D,L) lactic acid grafting. Differential scanning calorimetry shows that Tg of hydroxyapatite/poly (D,L) lactic acid composite is less than Tg of pure poly (D,L) lactic acid, which facilitates the shaping of the composite obtained. The addition of poly (D,L) lactic acid improves the adsorption properties of hydroxyapatite for fibronectin extracellular matrix protein. Furthermore, the presence of poly (D,L) lactic acid on hydroxyapatite surface coated with fibronectin enhanced pre-osteoblast STRO-1 adhesion and cell spreading. These results show the promising potential of hydroxyapatite/poly (D,L) lactic acid composite as a bone substitute material for orthopedic applications and bone tissue engineering.     

Treating contaminated soil by conversion into carbonaceous adsorbents: an investigation of activation procedures

The well established activated carbon manufacturing process has been investigated as a novel treatment for contaminated soil from gaswork sites by converting it into a porous carbonaceous solid with adsorbent properties. Several activation methodologies were evaluated: CO₂, air, ZnCl₂, H₂SO₄, H₃PO₄, FeSO₄ and HNO₃. Thermal analysis of the soil provided information regarding appropriate carbonisation and activation conditions. Bulk samples were prepared using contaminated soil samples, with ZnCl₂ being found to be the most effective agent for the process, producing an adsorbent which possessed a BET surface area of 131m²g⁻¹. The aqueous adsorption ability of the soil carbons was studied using phenol and 4‐nitrophenol as representative micropollutant organic molecules. The Langmuir monolayer capacity of the ZnCl₂‐activated soil was found to be 0.12 mmg⁻¹ for phenol and 0.23 mmg⁻¹ for 4‐nitrophenol. © 2000 Society of Chemical Industry     

Performance study of cementitious systems containing zeolite and silica fume: effects of four metal nitrates on the setting time,strength and leaching characteristics

The aim of this study is to investigate the effect of four metal nitrate contaminants, namely chromium, manganese, lead and zinc on the mechanical and leaching characteristics of cement-based materials. For this purpose, three different matrices made of: (i) Portland cement, (ii) Portland cement and silica fume, and (iii) Portland cement and natural zeolite were studied. The effects of metals on the stabilised/solidified (S/S) product characteristics were monitored by measuring: (i) setting time, (ii) compressive strength, (iii) acid neutralisation capacity (ANC), and (iv) solubility of the metal contaminants as a function of pH.The results of both mechanical and leaching tests showed the importance of the contaminant/matrix couple considered. Setting time was accelerated in presence of chromium, while in presence of manganese, lead and zinc it was delayed. However, for the last two contaminants, a 10% replacement of cement by silica fume and zeolite, markedly accelerated the setting time compared to the cement-only matrix. Although the early strength development was adversely affected in presence of all four contaminants, the long-term strength was less affected compared to the control materials. Although the ANC of the materials was not markedly affected by the presence of contaminants, the nature of the matrix did modify the ANC behaviour of the solidified materials. The increased strength and reduced ANC observed in the presence of silica fume are both due to pozzolanic reaction. The type of matrix used for solidification did not affect the solubility of the four metal contaminants. Overall, the results showed that the use of blended cements must be carried out with care and the performance assessment of waste-containing cement-based materials must take into consideration both the mechanical and leaching characteristics of the systems.     

Use of a liquid chemical waste to produce a clay–carbon adsorbent

The feasibility of producing an adsorbent from an alkaline aqueous tarry industrial waste has been investigated in this study. The inherent disadvantages of producing a solid carbonaceous material from a waste with its organic content in a dissolved state were overcome by neutralising the waste liquor to pH<2 in the presence of fuller's earth, filtering and producing a solid cake more suitable for thermal treatment. Optimisation of this procedure, followed by ZnCl₂ activation, produced clay–carbon adsorbents with surface areas of up to 225 m² g⁻¹ capable of adsorbing 28% of phenol and 35% of 4-nitrophenol from 10 mM aqueous solution. The potential of this procedure in a beneficial waste reduction and re-use context are highlighted. © 1998 SCI     

Magnetic resonance imaging of the effect of zeolite on lithium uptake in poplar

The use of a zeolite (clinoptilolite) to protect poplar plants from lithium-contaminated soil has been studied using magnetic resonance imaging. Lithium was used as a model contaminant as it could be tracked directly using specific nuclear magnetic resonance probes, rather than relying on relaxation time effects on protons due to paramagnetic solutes. The sorption of lithium to the zeolite was investigated both in static and dynamic systems; lithium was found to sorb readily to the zeolite over time. Poplar plants were grown in soil microcosms consisting of either sand or sand and zeolite with nutrients provided through the use of Hoagland's solution as the pore fluid. Both one-dimensional profiles of lithium concentration along poplar stems and direct lithium imaging of stem cross-sections were employed to reveal the uptake of the contaminant into the plant structure, showing significantly less lithium present in plants grown in sand and zeolite than those grown in sand alone. Evidence of structural features involved in the uptake of lithium was also obtained.     

Hydroxyapatite-TiO2-SiO2-Coated 316L Stainless Steel for Biomedical Application

Metallurgical and Materials Transactions A - This study investigated the effectiveness of titania (TiO2) as a reinforcing phase in the hydroxyapatite (HAP) coating and silica (SiO2) single layer as...     

Preliminary evaluation of polymeric Fe‐ and Al‐modified clays as adsorbents for heavy metal removal in water treatment

This paper assesses the potential of modified montmorillonite clays as low‐cost adsorbents/ion‐exchangers for the removal of trace level heavy metals (Cd, Cu, Ni, Pb and Zn) from potable water. Modification of the montmorillonites resulted in the exchange of the interlayer calcium ions for the polymeric species. One unmodified montmorillonite and three polymeric Fe‐ and Al‐modified montmorillonites have been evaluated with respect to their selectivity and uptake performance. All of the clays are selective for Pb and Cu adsorption from aqueous solutions at the mildly acidic pH range in which the experiments were performed (pH 5.5–6). Polymeric iron‐ and polymeric Al/Fe‐modified clays had comparatively great affinities for all the metals studied, whilst the original and polymeric Al modified clays had relatively lower affinities. Only the uptake of Pb and Cu could be correlated with physical properties such as clay surface area. The metal selectivity could be correlated to the type of intercalated polymeric Fe and Al species of the modified clays. © 2002 Society of Chemical Industry     

Use of activated carbon for the recovery of chromium from industrial wastewaters

A technique for the removal and recycling of hexavalent chromium from electroplating industries was developed. It involves a two-phase process which consists of (1) the use of an activated carbon bed for the accumulation of chromium onto the surface of activated carbon followed by (2) the regeneration of the carbon leading to a concentrated chromium solution with potential for reclamation or reuse within the plating operation. Results from continuous flow experiments showed that in excess of 99% chromium removal efficiency can be achieved. It was also revealed that regeneration of the exhausted carbon under acidic conditions recovered chromium in the trivalent state with concentrations as high as 3 g dm⁻³, more than 12 times the influent concentration. The adsorption capacity of the activated carbon was found to increase with successive cycles of adsorption/regeneration. However, when regeneration was achieved under alkaline conditions, the chromium was recovered in the hexavalent state with concentrations as high as 8·4 g dm⁻³, in excess of 33 times the chromium influent concentration. In addition, under caustic regeneration conditions, the data showed that the adsorption capacity in this case decreases with the increased number of exhaustion cycles. Mass balance calculation for both acid and caustic regeneration indicated that in both cases the regeneration process was incomplete with a recovery efficiency averaging around 50%. In an attempt to maximise the recovery efficiency, a combination of caustic followed by acid regeneration was applied to the exhausted activated carbon and the results led to a drastic improvement in the total recovery process (85–98%). These results clearly show that activated carbon is a viable candidate for the removal and recovery of chromium from electroplating industries. The critical advantage in the use of activated carbon is (1) the ability to regenerate and thus prepare a concentrated chromium solution for potential reclamation or recycle to the plating operation, and (2) the potential of avoiding the generation of hazardous sludge for land disposal. ©1997 SCI     

Membrane assisted technology appraisal for water reuse applications in South Africa

Water scarcity, pertaining to many interrelated issues e.g. rapid urbanisation and increasing water pollution, has been acknowledged around the world. Water reuse has emerged as a viable water conservation measure to satisfy water demand in many communities. Among the diversity of wastewater treatment processes, membrane assisted treatment technologies have been employed for different water reuse scenarios. In this regard, one of the most critical problems is how to select an appropriate membrane technology for a water reuse scenario. This research therefore develops a decision making framework for selection of wastewater treatment technology. The framework is applied to different non-potable reuse scenarios in South African cities and suburban areas by employing a multi criteria analysis method. The results show that this approach is able to provide a systematic and rigorous analysis which can help in comparing and selecting wastewater technologies.     

Permeation of Organic Chemicals Through Plastic Water-Supply Pipes

This paper discusses the problem of permeation of organic chemicals through plastic water-supply pipes, resulting in drinking-water contamination. Case studies are reported where contamination has resulted in taste and odour problems for customers, and might pose a risk to health. It is therefore recommended that (a) guidance is provided for water companies and building contractors, specifying when it is inappropriate to use unprotected plastic pipes for the provision of drinking water, and (b) measures are taken to ensure adherence to this guidance.