Copper, Cadmium and Ferrous Removal by Membrane Bioreactor

AbstractOne of the important concerns in Tehran municipal landfill is the production of leachate and its potential for water resources pollution. This paper investigates the removal of heavy metals from landfill leachate by using a membrane Bioreactor (MBR). The leachate was collected from a landfill in the vicinity of Tehran nearly 1 year old, The results of this study indicated that the system provided high removals of Fe, Cu and Cd equal to 96%, 23% and 84% respectively and heavy metal concentration in MBR effluent is a function of aeration ratio and bioaccumulation. Among the metals investigated in the present study it can be concluded that the extracellular adsorption, is the principal removal process of the metals, compared to other removal mechanisms such as bioaccumulation or intracellular accumulation

2-(4-Amino­phen­yl)-1-phenyl­diazenium 2,4,6-trinitro­phenolate

In the title salt, C12H12N3 +·C6H2N3O7 −, the diazenyl group of the 4-(phenyl­diazen­yl)aniline mol­ecule is protonated and forms a hydrogen bond with the phenolate O-atom acceptor of the picrate anion. Structure extension occurs through two symmetrical inter-ion three-centre amine N—H⋯O,O′nitro hydrogen-bonding associations [graph set R 1 2(4)], giving a convoluted two-dimensional network structure

Dicyclo­hexyl­ammonium hydrogen phenyl­phospho­nate

In the title salt, [(C6H11)2NH2]+·[C6H5PO2(OH)]−, the anion is monodeprotonated and acts as both a hydrogen-bond donor and acceptor. The anions are linked by pairs of O—H⋯O inter­actions, forming inversion dimers with R 2 2(8) ring motifs. These dimers are bridged by two dicyclo­hexyl­aminium cations via pairs of N—H⋯O hydrogen bonds, giving R 4 4(12) ring motifs, forming chains propagating along [010]. The chains are bridged by C—H⋯O inter­actions, forming a two-dimensional network lying parallel to (101)

Ammonium benzene­phospho­nate

In the crystal structure of the title salt, NH4 +.[(C6H5)P(O)2(OH)]− or NH4 +·C6H6O3P−, the N and O atoms inter­act via hydrogen bonds to generate a layer motif. The phenyl rings are stacked above and below this layer, sandwiching the hydrogen-bonded layer

Recycling Inorganic Residues from Wood-based Industries to the Forest- study of Treatment Techniques and Leaching Characteristics

Abstract. In order to minimize the negative impact of loss of nutrients in the forest soil (when harvesting the wood), inorganic solid residues, from wood-based industries, have to be recycled back to the forest soil. However, due to high alkalinity and a high dissolution rate of the elements, the residuals cannot be recycled without being treated into suitable and recyclable products. These products should meet the needs of forest soils without compromising the soil environment. For this purpose, it is necessary to measure and characterize the leaching rate of the product under well-defied conditions. The present study offers theories and methods for characterizing the products prior to recycling. A modified column-pHstat leaching test was developed in which the leaching tests could be performed under well controlled conditions. By using this leaching test, it was possible to make a more accurate evaluation of the leaching characteristics of the products than when using the common column test or batch test. The results of the laboratory leaching tests were then verified by performing field studies. It was found that by thoroughly characterizing the products prior to recycling, it was possible to estimate leaching trends in the field. It was concluded that by using a combination of well controlled experiments and mathematical modeling, it was possible to understand the different phenomena that control the leaching mechanism of both easily limited soluble species. Two different mechanisms were proposed for the leaching rate determining steps. A diffusional mass the transfer model could well describe the leaching rate of easily soluble species, while a heterogeneous reaction mechanism consisting of both surface reaction and mass transfer established the rate determining step for less soluble salts. The influence of treatment techniques on physical structure and leaching properties of the products were also investigated. Depending on the chemical composition of the products, as well as the operational condition during the treatment process, different leaching properties were achieved. It was found that by applying thermal treatment, the physical structure of products becomes harder and more stable than the physical structure of non-treated residues. One of the major findings was that in order to control the leaching of limited soluble species, the chemical structure of the Ca-salts should be modified to a less soluble salt. Moreover, the physical characteristics that correlate with the leaching properties of both easily and limited soluble species need to be adjusted

Simulation of a photochemical reactor for benzene elimination from waste gas

Bibliography: p. 97-104A considerable amount of BTEX (Benzene, Toluene, Ethyl-benzene and Xylene) is being emitted by oil and gas industry. New techniques such as photolysis could help the industry achieve present and future emission standards. In this work the feasibility of photolysis technique for BTEX removal from waste gas has been investigated. A simulation model has been developed for benzene photolysis in waste gas which includes a light field model, a chemical model, a flow pattern model and a mass transfer model. At air flow rates of 1.5 L/min and benzene concentrations ranging from I to IO g/m3 a likely concentration range for an industrial photolysis process, the model predicts a degradation rate of about 1.9-2 mg/min, in a 0.5 L reactor with a 40-watt UV lamp emitting 8% of its power consumption of 185 nm and 30% at 254 nm which amounts to about l kg benzene per year. This is slightly above the experimental results (1-1.5 mg/min) obtained in earlier work (M. Rezaei, internal report, U ofC, 2010). The model predicts that premixing ozone will increase the efficiency of the process dramatically. Simulations also show that condensation is a promising pre-treatment technique for this process. Based on energy requirement calculations, it is concluded that the combination of condensation, ozone pre-mixing and UV photolysis is economically feasible