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We have developed the hybrid jig which combines the principles of jig separation and flotation. However, the selectivity of bubble attachment in water was poor because most plastics have inherently hydrophobic surfaces; so, development of surface modification techniques for plastic particles would expand the application of hybrid jig to the material recycling of plastics. In this study, hybrid jig separation of polypropylene using glass fiber and high impact polystyrene having similar specific gravities and surface wettability were investigated with three wetting agents [Di-2-ethylhexyl sodium sulfosuccinate (Aerosol OT, AOT), sodium lignin sulfonate, and tannic acid]. The results showed that the probability of bubble attachment was influenced by wetting agents because of their strong effects on the surface tension of solution and surface wettability of plastics. The results also suggest that wetting agents could be utilized to control the selectivity of bubble attachment and improve the hybrid jig separation efficiency. In addition, since the hybrid jig separation of polyvinyl chloride and polyamide (nylon-66) using AOT was imperfect, a two-step approach, composed of a pre-wetting step (first step) in a solution containing the wetting agent (AOT) and hybrid jig separation in water (second step), is proposed.

Influence of particle shape on hydrocyclone classification was investigated. Classification tests using hydrocyclone and cyclosizer showed that coarse fractions of plate-like particles such as PTFE and glass flake used here were not necessarily recovered as underflow product, especially at relatively high inlet velocity. Settling velocity of the glass flake particles in centrifugal field was estimated using a centrifugal particle size analyzer, and it was revealed that differences in settling velocity between coarse and fine glass flake particles became smaller with increases in angular velocity. Moreover, settling test of glass plate in water or glycerin solution was conducted to know relationship between particle Reynolds number (Re) and settling velocity of the plate. At smaller Re condition, the glass plate settled straight and stably, and larger plate settled faster than smaller plate. However, oscillating motion of the plate occurred in the region of high Re, and settling velocities of the large plate became smaller than that of the small plate in such conditions. Drag coefficient (C) calculated based on the settling velocity of the glass plate is similar to that of glass spheres below Re of about 50, above which it became larger than that of glass sphere. Approximation formula of correlaton between Re and C suggests that the influence of the Re on C can be neglected in the region of high Re, and C increases with increases in the ratio of the particle diameter to thickness (D/T). The decrease of the difference in settling velocity recognized in the centrifugal settling test and the effect of the particle shape (D/T) on C at high Re region are considered to be able to affect the hydrocyclone classification. The misplacement of coarse plate-like particles in the hydrocyclone and cyclosizer tests could be ascribed to the particle shape effects.

Recycling treatment of cable insulation resin generated from electric wires and cables was investigated. Here, PVC is the most common insulation resin and conventional insulation PVC contains a lead component, tribase, as a thermal stabilizer. To recycle this PVC as insulation resin, lead removal is necessary to be able to conform to RoHS. This paper proposes a solvent dissolution and centrifugation method and the effects of flocculants and water addition in the processes involved are described.

The jig is efficient in separating relatively low density particles such as plastics; however conventional discharge devices attached to jigs cause mechanical disruption of the stratified layers at the outlet from the separation chamber, and decrease the grade of the recovered bottom layer product. A new device was developed for efficiently separating high grade bottom layer product, better than 99%, where particles of the bottom and top layers are recovered as overflow products by agitation with water pulsation.

The jig is efficient in separating relatively low density particles such as plastics; however conventional discharge devices attached to jigs cause mechanical disruption of the stratified layers at the outlet from the separation chamber, and decrease the grade of the recovered bottom layer product. A new device was developed for efficiently separating high grade bottom layer product, better than 99%, where particles of the bottom and top layers are recovered as overflow products by agitation with water pulsation.

Acid mine drainage (AMD) is formed from the natural oxidation of sulfide minerals such as pyrite, FeS2. Prevention of acid mine drainage is very important and several techniques are currently being investigated for the treatment and abatement of AMD. This paper proposes carrier-microencapsulation (CME) using Si-catechol complex -Si(cat)3^[2-]- for preventing pyrite oxidation. In CME, the water soluble organic carrier- catechol and metal ion-Si makes a complex e.g., tris-catecholato complex of Si4+, which oxidatively decomposes on pyrite surface and forms a stable oxide or hydroxide e.g., Si(OH)4 or SiO2 layer on the pyrite surface as a protective coating against pyrite oxidation. To demonstrate the effect of CME using Si(cat)3^[2-] on pyrite oxidation, shaking-flask leaching experiments of pyrite without and with CME treatment were performed. Significant halt in pH drop was observed after the CME treatment of pyrite. The CME coating was found very effective even at low Si(cat)3^[2-] concentration of 1 mol m^[-3] and 5 mol m^[-3]. The amount of Fe and S leached were lower from the pyrite with CME treatment, indicating that CME using Si and catechol is effective in suppressing pyrite oxidation. The effect of pH and presence of microorganism were also evaluated. The CME coating was found very effective even in acidic pH range. The CME treatment suppressed pyrite oxidation even in the presence of iron oxidizing microorganism. Presence of Si and O on the residue pyrite surface in SEM-EDX analysis supported the sustainability of CME coating at acidic pH.

The sorption of gold chloride (AuCl4 ) from chloride solution on synthetic and natural magnetite powders was investigated by batch sorption experiments. The effects of different parameters on the recovery were studied. The results showed that Gold (Au) uptake by magnetite was influenced by pH, contact time, chloride concentration, and initial Au concentration. Gold uptake by synthetic and natural magnetite was maximum at pH 6–7 with sorption amounts of 4.4 lmol/g and 5.0 lmol/g, respectively, after 24 hr at an initial Au concentration of 0.05 mol/m3. The Scanning Electron Microscopy–Energy Dispersive X-ray and Back Scattering Electron analyses of the magnetite particles after treatment confirmed the presence of Au precipitates on the magnetite (Fe3O4) surface.

Recycling has gained attention nowadays due to the increasing awareness in sustainable development. The recycling of waste plastics has become one of the priorities because of the rising consumption and generation of plastic wastes from different sectors of the society. Waste plastics are composed of a mixture of different types of plastics and need to be separated before they can be recycled. Several techniques were investigated or developed to separate plastics and one of them is jig separation. Jig separation is based on the displacement of particles in a bed fluidized by the pulsation of the fluid in a vertical plane so as to produce stratification. The principles behind jigging are governed by physics, particularly the motion of particles in fluid. This paper presents the theories proposed to effect particle separation by jigging. Studies on the application of jigging to separate different kinds of plastics were reviewed. It can be concluded that jig separation can be applied for plastic separation and recycling. However, more research and development effort is required before a commercial scale application can be established.

Molten fly ash (MFA), generated by the melting process of municipal solid waste incineration (MSWI) solid residues in Japan, contains considerable amounts of heavy metals such as Pb, Zn, Cu and Cd. Therefore, MFA is classified as a hazardous waste and needs treatment for detoxification or recovery of heavy metals as secondary sources. Carrier-in-Pulp (CIP) method, which is similar in principle with the Carbon-in-Pulp technology for gold recovery from ores, was proposed to recover these heavy metals from molten fly ash. Unlike the traditional Carbon-in-Pulp process, the carrier or adsorbent in the Carrier-in-Pulp method is not only limited to carbon; other materials such as Fe powder can also be used. Moreover, other physical separation techniques such as magnetic separation can also be employed to harvest the carrier from the leach pulp.The present study, which can be regarded as a batch mode Carbon-in-Pulp process, investigated the application of the CIP technique to recover heavy metals from MSW molten fly ash containing 10.2 wt.% Zn,2.78 wt.% Pb, 0.14 wt.% Cu, and 0.12 wt.% Cd. Granular activated carbon (GAC) was utilized as an adsorbent in batch adsorption tests and experiments involving the CIP method using NaCl as lixiviant. The effects of activated carbon dosage, pH, NaCl concentration, and treatment time were determined. Adsorption tests showed that the competition of metal ions present in a multi-component system suppressed the adsorption of Pb, Zn, Cu and Cd on GAC but the suppression can be minimized by increasing the GAC dosage. Around 90–100% of Pb, Zn, Cu and Cd were extracted from MFA at various conditions. At the optimum conditions (5 kmolm-3NaCl,10 g GAC, pH 5–6, and 3 h treatment time), GAC recovered 57% Zn, 40% Pb, 90% Cu, and 54% Cd. The leaching test confirmed that the extraction of Pb from the CIP-treated residue was below the standard, thus, satisfying the land-filling guidelines in Japan.

Municipal solid waste (MSW) molten fly ash is classified as a hazardous waste because it contains considerable amount of heavy metals, which pose environmental concern due to their leaching potential in landfill environments. This study proposes Carrier-in-Pulp (CIP) method as a new hydrometallurgical route to extract and recover Pb, Zn, Cu, and Cd from molten fly ash before landfilling. In this method, a carrier material, which recovers the extracted metals, is added simultaneously with fly ash to a leaching solution and is harvested from the pulp by physical separation method, such as magnetic separation or sieving. To demonstrate the effect of the CIP method, shaking flask experiments were conducted under various conditions using NaCl solution, iron powder as carrier, and molten fly ash. More than 99 wt% Pb, Zn, and Cd, and 97 wt% Cu were extracted from the ash. However, only Pb and Cu were recovered (96.3 wt% Pb and 94.3 wt% Cu) by the iron powder through cementation, leaving behind Zn and Cd ions in the solution phase. The leaching test conducted on the treated fly ash residue revealed that the CIP method suppressed the solublization of Pb to values below the landfill disposal guideline.

Water-related damage is one of the major problems for the durability of the bituminous pavement and concrete slabs of concrete deck bridges. In particular, damage can be drastically accelerated by the intervention of water and some chemicals such as surfactants and salts. Therefore, the mass transfer mechanism of water and the mechanism of chemical absorption in pavement materials are important to study. The authors previously pointed out that water storage in bituminous pavement layers is caused by moisture vapor in the air, and developed a new moisture permeation test apparatus to analyze the mass transfer. Based on this test method, the present study showed experimentally that water and surfactant accumulate in the bridge deck pavement and concrete slabs. Water accumulation in the pavement and deck slabs increases according to the daily climatic fluctuation. The repetitive moisture permeation test showed that alkylphenol-ethoxylate type surfactant applied on the top surface permeates through water-impermeable pavement layers and accumulates in the concrete slab.

Water-related damage is one of the major problems for the durability of the bituminous pavement and concrete slabs of concrete deck bridges. In particular, damage can be drastically accelerated by the intervention of water and some chemicals such as surfactants and salts. Therefore, the mass transfer mechanism of water and the mechanism of chemical absorption in pavement materials are important to study. The authors previously pointed out that water storage in bituminous pavement layers is caused by moisture vapor in the air, and developed a new moisture permeation test apparatus to analyze the mass transfer. Based on this test method, the present study showed experimentally that water and surfactant accumulate in the bridge deck pavement and concrete slabs. Water accumulation in the pavement and deck slabs increases according to the daily climatic fluctuation. The repetitive moisture permeation test showed that alkylphenol-ethoxylate type surfactant applied on the top surface permeates through water-impermeable pavement layers and accumulates in the concrete slab.