An eco-friendly process: Predictive modelling of copper adsorption from aqueous solution on Spirulina platensis

The adsorption of copper ions on Spirulina platensis was studied as a function of contact time, initial metal ion concentration, and initial pH regimes. Characterization of this adsorbent was confirmed by FTIR spectrum. Modified Gompertz and Logistic models have not been previously applied for the adsorption of copper. Logistic was the best model to describe experimental kinetic data. This adsorption could be explained by the intra-particle diffusion, which was composed of more than one sorption processes. Langmuir, Freundlich, and Redlich–Peterson were fitted to equilibrium data models. According to values of error functions and correlation coefficient, the Langmuir and Redlich–Peterson models were more appropriate to describe the adsorption of copper ions on S. platensis. The monolayer maximum adsorption capacity of copper ions was determined as 67.93 mg g^?1. Results indicated that this adsorbent had a great potential for removing of copper as an eco-friendly process.     

Synergistic Role of Pumice Surface Composition in Hydroxyl Radical Initiation in the Catalytic Ozonation Process

This study investigated the catalytic ozonation of p-chloronitrobenzene (p-CNB) in aqueous solution by using different pumice surface compositions as catalysts. The results indicate that the surface hydroxyl groups of metal oxides on pumice play an important role in ozone decomposition to generate the hydroxyl radical (?OH). An increase in the mass ratio of SiO₂/metal oxides results in the acceleration of ozone adsorption on the catalyst surface. The synergistic mechanism confirms that SiO₂ induced ozone enrichment on the pumice surface and increased the probability of reaction between surface hydroxyl groups on metal oxides and ozone molecules to initiate ?OH from ozone decomposition and to stimulate p-CNB degradation.     

Biosorption mechanism of Zn2+ from aqueous solution by spent substrates of pleurotus ostreatus

To solve the problem of heavy metal pollution and agricultural wastes reclamation, spent substrate of pleurotus ostreatus (SSPO) was used as adsorbent to remove Zn²⁺ from aqueous solution. The biosorption of zinc ions on SSPO was studied as a function of the solution pH, temperature and initial Zn²⁺ concentration. The equilibrium sorption data were well represented by linear Langmuir isotherm models with R² value of 0.9955 and non-linear Freundlich with R² value of 0.9973. The BET surface area of SSPO can reach 51.16m²g^?1. SEM-EDX and XRD revealed that (NH₄)₂Zn·H₂O and Zn₂PO₄(OH) were the main compounds in metal-loaded SSPO. FTIR analysis indicated the governing functional groups such as O-H, N-H and P=O played an important role in biosorption. The desorption studies showed the reversibility of SSPO. The results indicate that SSPO is a potential adsorbent in wastewater treatment due to its great sorption capacity and low cost.     

A review of the IEA/NEA Projected Costs of Electricity – 2015 edition

The IEA/NEA recently issued their eighth edition of the Study on the “Projected Costs of Generating Electricity” – 2015 edition. The Study is mainly concerned with calculating the levelised cost of electricity (LCOE). The LCOE calculations are based on a levelised average life time cost approach using the discounted cash flow (DCF) method. The analysis was this year, and for the first time, performed using three discount rates (3%, 7%, and 10%). The LCOE can serve as a tool for calculating the cost of different generation technologies. However the Study's usefulness is affected by its narrow base of a limited set of countries that are not necessarily representative. It ignored the negative role of subsidies and did not provide a methodology for selective application of the discount rates and costing of carbon. The global power generation scene is changing. Generation growth in OECD countries has become very limited; simultaneously there is rapid growth of varying renewables (VRE) generation which needs special criteria for assessing its system cost. All this demands a rethinking of the application and usefulness of the LCOE in future generation planning.     

Evaluation of fly‐ash additive for removal of dissolved organic matter during soil aquifer treatment of wastewater treatment plant Peffluent

BACKGROUND: Fly‐ash (FA) additive was evaluated for enhanced removal of organic matter during soil aquifer treatment (SAT) of a wastewater treatment plant (WWTP) effluent in five 0.50 m length columns (diameter 0.1 m) in parallel. RESULTS: The characteristic behavior of dissolved organic matter (DOM) was examined for the stratum matrix configurations of both natural soil and a mixture of soil and FA. Incubation and fractionation experiments indicated that FA additive within the SAT columns would enhance the bulk adsorption of hydrophobic fractions, but decrease the biodegradation of the hydrophilic fraction simultaneously. The configuration design of an upper 0.25 m soil layer and a mixture of FA and soil underneath could make use of the functions of both FA adsorption and biodegradation within soil, which could lead to a further fractional removal of dissolved organic carbon (DOC) and trihalomethane formation potential (THMFP). Moreover, FA additive in the SAT columns could result in a significant decrease of tryptophan‐like aromatic proteins and fulvic‐like components (C?C and C?O related), while the setting of the top 25 cm soil layer would lead to a further reduction of oxygen‐containing functional groups. CONCLUSIONS: Based on the results, FA might serve as a supplementary material for enhancing the reduction of DOM during SAT operation. Copyright © 2010 Society of Chemical Industry     

Influence of surface texture and acid–base properties on ozone decomposition catalyzed by aluminum (hydroxyl) oxides

The decomposition of aqueous ozone in the presence of three aluminum (hydroxyl) oxides was studied, respectively. It was hypothesized that surface hydroxyl groups and acid–base properties of aluminum (hydroxyl) oxides play an important role in catalyzed ozone decomposition. The variables investigated were oxide dose, aqueous pH, presence of inorganic anions (sulfate and nitrate), the effect of tert-butyl alcohol (TBA) and surface hydroxyl groups density of the three aluminum (hydroxyl) oxides. All three aluminum (hydroxyl) oxides tested, i.e. γ-AlOOH (HAO), γ-Al₂O₃ (RAO) and α-Al₂O₃ (AAO), enhanced the rate of ozone decomposition. The net surface charge of the aluminum (hydroxyl) oxides favored in catalyzed ozone decomposition. The greatest effect on catalyzed ozone decomposition was observed when the solution pH was close to the point of zero charge of the aluminum (hydroxyl) oxide. Sulfate and nitrate were substituted for the surface hydroxyl groups of the aluminum (hydroxyl) oxides, which then complexed with Al³⁺ in a ligand exchange reaction. Therefore, inorganic anions may be able to inhibit catalyzed ozone decomposition. It was confirmed that surface hydroxyl groups were important for ozone decomposition with aluminum (hydroxyl) oxides as catalysts. TBA inhibited ozone decomposition in the presence of HAO, RAO and AAO. It was also tested whether aluminum (hydroxyl) oxides catalyzed ozone-transformed hydroxyl radicals. The relationship between surface hydroxyl groups and the ratio of hydroxyl radical concentration to ozone concentration (R_ct) was investigated quantitatively. Higher density of surface hydroxyl groups of the aluminum oxide tested was favorable for the decay of ozone into hydroxyl radicals.     

Evolutionary learning of fuzzy models

This paper presents an evolutionary algorithm for generating knowledge bases for fuzzy logic systems. The algorithm dynamically adjusts the focus of the genetic search by dividing the population into three sub-groups, each concerned with a different level of knowledge base optimisation. The algorithm was tested on the identification of two highly non-linear simulated plants. Such a task represents a challenging test for any learning technique and involves two opposite requirements, the exploration of a large high-dimensional search space and the achievement of the best modelling accuracy. The algorithm achieved learning results that compared favourably with those for alternative knowledge base generation methods.     

Simultaneous nitrification and denitrification process in a new Tubificidae-reactor for minimizing nutrient release during sludge reduction

Nutrient release is reported as one of the main disadvantage of sludge reduction induced by aquatic worm. In this study, a Static Sequencing Batch Worm Reactor (SSBWR) was proposed with novel structure of perforated panels, combined aeration system and cycle operation. Effective simultaneous nitrification and denitrification were obtained owing to the stratified sludge layer containing aerobic and anoxic microzone formed on each carrier during most of the operation time in the SSBWR, which created suitable conditions for remarkable sludge reduction and nutrient removal. The results showed that the total nitrogen (TN) concentration, NO₃^?–N + NO₂^?–N concentration and NH₄⁺–N release could be reduced by 67.5%, 98.5% and 63.0%, respectively. And the soluble chemical oxygen demand (sCOD) released by sludge predation was also proved to provide a carbon source for denitrification leading to carbon release control and substantial cost savings. A schematic diagram of the stratified sludge layer and the mass balance of the nitrification–denitrification cycle were given, providing further insight into the nutrient (sCOD and nitrogen compounds) transformation during the worm predation in the SSBWR. For the mixed sludge liquid of 3000 mg TSS/L, 30 mg/L sCOD and 40 mg/L NO₃^?–N, the NO₃^?–N and NO₂^?–N came close to zero, and the sludge concentration, NH₄⁺–N release and sCOD release was reduced by 33.6%, 63.0% and 72.5%, respectively, during 48 h’ predation.     

Formation of carbonaceous and nitrogenous disinfection by-products from the chlorination of Microcystis aeruginosa

Formation of carbonaceous disinfection by-products (C-DBPs), including trihalomethanes (THMs), haloacetic acids (HAAs), haloketones (HKs), chloral hydrate (CH), and nitrogenous disinfection by-products (N-DBPs), including haloacetonitriles (HANs) and trichloronitromethane (TCNM) from chlorination of Microcystis aeruginosa, a blue-green algae, under different conditions was investigated. Factors evaluated include contact time, chlorine dosages, pH, temperature, ammonia concentrations and algae growth stages. Increased reaction time, chlorine dosage and temperature improved the formation of the relatively stable C-DBPs (e.g., THM, HAA, and CH) and TCNM. Formation of dichloroacetonitrile (DCAN) followed an increasing and then decreasing pattern with prolonged reaction time and increased chlorine dosages. pH affected DBP formation differently, with THM increasing, HKs decreasing, and other DBPs having maximum concentrations at certain pH values. The addition of ammonia significantly reduced the formation of most DBPs, but TCNM formation was not affected and 1,1-dichloropropanone (1,1-DCP) formation was higher with the addition of ammonia. Most DBPs increased as the growth period of algal cells increased. Chlorination of algal cells of higher organic nitrogen content generated higher concentrations of N-DBPs (e.g., HANs and TCNM) and CH, comparable DCAA concentration but much lower concentrations of other C-DBPs (e.g., THM, TCAA and HKs) than did natural organic matter (NOM).     

Dechlorination of chlorophenols mediated by carbon nanotubes in the presence of oxygen

Using chlorophenols as probe compounds, we examined the occurrence of oxidative coupling during carbon nanotube adsorption of phenolic compounds in the presence of oxygen. The oxidative coupling was confirmed by the agreement of the dechlorination stoichiometries of various chlorophenols with the free-radical mechanism of oxidative coupling. The oxidative coupling reaction was first-order with respect to chlorophenols on carbon nanotubes and increased with the increase of pH.