China PARTICUOLOGY

Increasing population and individual wealth have led to a higher demand for energy and raw material resources as well as for steady improvement of processing technology in view of efficient use of resources and avoiding emissions in production and recycling processes. Present situation and future trend of recycling processing are discussed by examples from the aluminium and steel industries, recycling of cars and post-consumer municipal recovery. The importance of more intense observance of thermodynamic laws and of a 4E strategy "Economy, Energy, Environment and Education" is outlined.

Graft copolymers of sodium alginate (SA) with acrylamide (AM) were synthesized using a ceric ion initiated solution polymerization technique. The acrylamide conversions were studied by changing reaction conditions, such as temperature, molecular weight of sodium alginate and reaction time. The flocculation performance of the graft copolymer (SAG) was investigated in kaolin suspension and also in dyeing waste water. It was found that SAG is more efficient in flocculation behavior as compared to polyacrylamide and SA in kaolin suspension, and in removal capacities for COD_Cr and colority in dyeing wastewater.

This paper investigates a treated fly ash to act as a synthetic zeolite to remediate soils polluted with heavy metals and metalloids (As, Pb, Cu, Zn, Fe, Cd and Mn). Four types of such 'zeolites' were synthesized by hydrothermal treatment of a calcareous fly ash derived from Greek lignite-fired power plants: two with excess of sodium hydroxide in a solid/liquid ratio of 50 g.L^-1, and two with excess of fly ash in a solid/liquid ratio of 100g.L^-1. Soil samples were obtained from a former mining site at Lavrion, Greece. Mobilization and transfer of metals to the retention agents was effected by using HCl aq 1M, with satisfactory results with respect to As, Pb, Cu, Mn, andCd. The great variety of metal complexes in soil was found to be of major importance for the effectiveness of the overall process. The final products were solidified either on their own, or by using additives such as lime and cement.

Nanofibrous carbonaceous materials (NFC) as a new class of materials having many applications, can catalyze the selective oxidation of H₂S, to sulfur. The correlation between NFC structure and its activity and selectivity in H₂S oxidation was determined. It is demonstrated that selectivity can be improved if NFC with more ordered structure be synthesized and the portion of the original catalyst in carbon be reduced by increasing the carbon accumulated in the catalyst.

Advanced technological achievements and the continuous growth of economy have made the disposal, recycle and reuse of industrial by-products a severe challenge. The cement industry is considered one of the key sectors in this effort in successfully (in terms of not extenuating but improving some of the properties of the final product) absorbing large quantities of solid wastes, either as aggregates or as secondary cementitious materials. This not only contributes to the creation of an energy and CO₂-emission depository (as commonly used raw materials are spared), but also simultaneously alleviates the acute environmental burden caused by the irresponsible disposal of such by-products. In this study, the possibility of reusing spent fluid catalytic-cracking catalyst (FCC) as a supplementary cementing material (SCM) was examined. A series of tests were conducted, initially aiming at characterizing the material and thereafter evaluating its pozzolanic activity and its effect on the mechanical properties of blended cements. Major findings in this investigation revealed that the use of FCC as a mineral admixture in cement is feasible, strengthening the belief that si-liceous glassy residues should represent a steady supply for the construction sector.

Influencing factors on bioaccumulation of Ni by Synechcoccus were studied in this paper. The equilibration time of Ni bioaccumulation was about 80 min in aqueous solution. Bioaccumulation quantity reached maximum when mass ratio of Ni to dry weight concentration of Synechcoccus was 16-18%. Bioaccumulation quantity increased with increasing pH. The optimum pH was 9-10 and higher pH led to precipitation of Ni(OH)₂. Bioaccumulation quantity was also influenced by temperature and light intensity reaching their optima at 35°C and 3 000 lx respectively. Bioaccumulation of nonliving algae was larger than that of living algae.

In the last 20 years, it has become apparent that waste produced from plastics was becoming an environmental problem because of their low biodegradability. Though several methods have been proposed for recycling waste plastics, it is generally accepted that material recovery is not a long-term solution to the present problem, and that energy or chemical recovery is a more attractive alternative, including cracking into the monomer constituents, combustion to produce energy, and thermal or catalytic conversion to produce useful intermediate chemicals.

This paper is a contribution in the area of the last option for energy recovery. There have been a number of publications reporting the use of molecular sieves and amorphous silica-alumina catalysts for the cracking of polymers into a range of hydrocarbons. The research work reported here demonstrates the ability of mesoporous catalysts in cracking polyethyl-ene into gasoline range products.

It was found that for mesoporous MCM-41 catalysts, its cracking activity increases with its crystallinity, displaying higher activity with smaller pore diameters. The hydrocarbon product distribution strongly indicates a carbenium ion cracking mechanism. The product distribution was also compared with those obtained from thermal cracking tests.

The aim of the present paper was to investigate the possibility of utilizing Construction and Demolition (C&D) wastes as substitutes of Portland cement raw meal. The C&D wastes that were so used, were the Recycled Concrete Aggregates (RCA) and the Recycled Masonry Aggregates (RMA) derived from demolished buildings in Attica region, Greece. RCA and RMA samples were selected because of their calcareous and siliceous origin respectively, which conformed the composition of the ordinary Portland cement raw meal. For that reason, six samples of cement raw meals were prepared: one with ordinary raw materials, as a reference sample, and five by mixing the reference sample with RCA and RMA in appropriate proportions. The effect on the reactivity of the generated mixtures, was evaluated on the basis of the free lime content (fCaO) in the mixtures sintered at 1350°C, 1400° C and 1450°C. Test showed that the added recycled aggregates improved the burnability of the cement raw meal without affecting negatively the cement clinker properties. Moreover, the formation of the major components (C₃S, C₂S, C₃A and C₄F) of the produced clinkers (sintered at 1450°C) was corroborated by X-Ray Diffraction (XRD).

The fate of different trace elements and radio nuclides in the new ZWILAG nuclear waste treatment plant (Switzerland) has been modelled, in order to predict and check the transport behaviour of the volatile species and their distribution in the plant. Calculations show that for active waste from medicine, industry, research (MIR waste) only Zn and Cs have stable gaseous species at 1200°C. The investigations confirm the efficiency of the examined flue gas cleaning system.

Sol-gel-derived nano-powders of lead magnesium niobate and lead titanate solid solutions (PMN-PT or PMNT) were prepared from lead acetate trihydrate (Pb(CH₃COO)₂3H₂O), magnesium acetate trihydrate (Mg(CH₃-COO)₂3H₂O), niobium ethoxide (Nb(OC₂H₅)₅) and titanium isopropoxide (Ti(OCH(CH₃)₂)₄). The key steps in the preparation process were discussed. The crystalline phases in the powders were investigated using X-ray diffraction (XRD) analysis and the size of grains was observed by field-emission scanning electron microscopy (SEM). These powders, with good dispersion characteristics and narrow grain size distribution (ranging from 50 nm to 200 nm), may be used to prepare PMNT thick films and ceramics.

In nature, microbes are involved in weathering of rocks, in mobilization of metals from minerals, and in metal precipitation and deposition. These microbiological principles and processes can be adapted to treat particulate solid wastes. Especially the microbiological solubilization of metals from solid minerals (termed bioleaching) to obtain metal values is a well-known technique in the mining industry. We focus here on non-mining mineral wastes to demonstrate the applicability of mining-based technologies for the treatment of metal-containing solid wastes. In the case study presented, microbial metal mobilization from particulate fly ash (originating from municipal solid waste incineration) by Acidithiobacilli resulted in cadmium, copper, and zinc mobilization of >80%, whereas lead, chromium, and nickel were mobilized by 2, 11 and 32%, respectively. In addition, the potential of HCN-forming bacteria (Chromobacterium violaceum, Pseudomonas fluorescens) was investigated to mobilize metals when grown in the presence of solid materials (e.g., copper-containing ores, electronic scrap, spent automobile catalytic converters). C. violaceum was found capable of mobilizing nickel as tetracyanonickelate from fine-grained nickel powder. Gold was microbially solubilized as dicyanoaurate from electronic waste. Additionally, cyanide-complexed copper was detected during biological treatment of shredded printed circuit-board scraps. Water-soluble copper and platinum cyanide were also detected during the treatment of spent automobile catalytic converters.

A novel method of fabricating composite mosaic membranes was studied on the basis of interfacial polymerization (IP) by coating a thin selective layer onto the surface of a micro-porous hollow-fiber membrane, in which, 2,5-diaminobenzene sulfonic acid was used as one monomer of the IP reaction, and a mixture of trimesoyl chloride (TMCl) and 4-(chloromethyl) benzoyl chloride as the other monomer. Through the IP reaction a thin selective layer with negatively charged groups could be first formed on the polyethersulfone (PES) support membrane. Then trimethylamine solution was introduced to modify the IP layer through a quaternization reaction. Thus the selective layer of this composite membrane contained both negatively charged and positively charged groups to perform the mosaic functionality. Characterization of the composite mosaic membranes was carried out through permeation experiments using different inorganic salts and dyes. The experimental results showed that the membranes could permeate both mono- and bi-valent inorganic salts, but reject larger organic molecules. Such a mosaic membrane is potentially useful for the separation of salts from water-soluble organics, especially in dye and textile industries.