Adsorptive removal of Pb2+ form aqueous solution by macrocyclic calix[4]naphthalene: kinetic, thermodynamic, and isotherm analysis

Background

The adsorption characteristics of Pb²⁺ ions from aqueous solutions onto calix[4]naphthalene have been investigated.

Method

Calix[4]naphthalene was prepared by the condensation of 1-naphthol and formaldehyde (1:2) in presence of hydrochloric acid at 80°C. The effect of various operation parameters, such as solution pH, initial metal ion concentration, contact time, and temperature, on the adsorption capacity of calix[4]naphthalene for Pb²⁺ have been investigated.

Result

Experimental results showed that the adsorption of Pb²⁺ ions increased with the increase in solution pH and temperature. Langmuir and Freundlich isotherms models were used to describe the adsorption behavior of Pb²⁺ by calix[4]naphthalene. Equilibrium data fitted well with the Langmuir isotherm model and the maximum adsorption capacity of calix[4]naphthalene for Pb²⁺ at 30°C was found to be 29.15 mg g^?1. Kinetic studies indicated that the adsorption followed pseudo-second order model and the thermodynamic studies revealed that the adsorption process was spontaneous and endothermic in nature. The obtained results demonstrated that calix[4]naphthalene can be used as an effective adsorbent for Pb²⁺ ions removal from water.     

Laboratory study on solidification/stabilization of unwanted medications using asphalt as a binder

The rise in discarded or unwanted medications (UMs) is becoming an issue of great concern, as it has the potential to harm the components of the environment where it is discarded: particularly air, water and soil. To combat this problem, many researchers have investigated the best approach for the collection and proper disposal of UMs. This paper intends to elaborate upon a safe solution for treating this waste, specifically through a process of solidification/stabilization (S/S) that involves mixing UMs with asphalt cement and asphalt concrete mixtures. Volumes of 5, 10, 15 and 20 % of a mixture of UMs were mixed with asphalt cement and the analyzed properties of the mixture of UMs–asphalt included: softening point, ductility, penetration, flash and fire points, specific gravity and rotational viscosity. Marshal stability, flow, air voids, unit weight, voids in mineral aggregate (VMA) and voids filled with binder (VFB) of asphalt concrete mixture were also investigated. Results showed that this approach of S/S is a promising method for dual achievements to solve an environmental problem and to use the waste for road construction.     

Optimal production scale of open pit mining operations with uncertain metal supply and long-term stockpiles

An open pit mining operation consists of various stages, and the calculation of the production capacities of these stages depends upon the available supply of ore (mineralized material of economic value) and waste material. Cutoff grade is the criterion that specifies the amount of ore and waste. The material with grade equal to or higher than the cutoff grade is classified as ore. The material with grade less than the cutoff grade is considered waste. While this explains the link between cutoff grade theory and the calculation of production capacities, the majority of optimization models for finding production capacities not only disregards this relationship but also ignores expected variations and uncertainty in metal content or the available supply of ore and waste material.     

Phytoremediation of an aged petroleum contaminated soil using endophyte infected and non-infected grasses

Phytoremediation is a promising technique for cleaning petroleum contaminated soils. In this study, the effects of two grass species (Festuca arundinacea Schreb. and Festuca pratensis Huds.), infected (E(+)) and non-infected (E(-)) by endophytic fungi (Neotyphodium coenophialum and Neotyphodium uncinatum, respectively) on the degradation of petroleum hydrocarbons in an aged petroleum contaminated soil was investigated. Plants were grown in the soil for 7 months and unplanted soil considered as control. At the end of the experiment, total and oil-degrading bacteria, dehydrogenase activity, water-soluble phenols, total petroleum hydrocarbons (TPH) and polycyclic aromatic hydrocarbons (PAHs) contents were measured in the soil. The results demonstrated that E(+) plants contained more root and shoot biomass than E(-) plants and created higher levels of water-soluble phenols and dehydrogenase activity in the soil, while there was no significant difference in bacterial counts of planted soils. Planting stimulated total and oil-degrading bacterial numbers, dehydrogenase activity and the soil content of water-soluble phenols. Regardless of endophyte infection, PAH and TPH removal in the rhizosphere of plants were 80-84 and 64-72% respectively, whereas the removals in controls were 56 and 31%, respectively. It was revealed that TPHs in retention time range of n-alkanes with C(10)-C(25) chain lengths and TPH were more degraded in the rhizosphere of E(+) plants compared to E(-) ones. Thus, grasses infected with endophytic fungi could be more efficient for removal of TPH from oil-contaminated soils.     

Geostatistical Assessment of the Impact of World War I on the Spatial Occurrence of Soil Heavy Metals

Previous research showed a regional Cu enrichment of 6 mg kg⁻¹ in the top soil of the Ypres war zone (Belgium), caused by corrosion of WWI shell fragments. Further research was required since in addition to Cu, also As, Pb, and Zn were used during the manufacturing of ammunition. Therefore, an additional data collection was conducted in which the initial Cu data set was tripled to 731 data points and extended to eight heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) which permitted (1) to evaluate the environmental impact of the heavy metals at a regional scale and (2) to assess their regional spatial occurrence by performing an optimized geostatistical modeling. The results showed no pollution at a regional scale, but sometimes locally concentrations exceeded the soil sanitation threshold, especially for Cu, Pb, and Zn. The spatial patterns of Ni and Cr were related to variations in soil texture whereas the occurrences of Cu and Pb were clearly linked to WWI activities. This difference in spatial behavior was confirmed by an analysis of coregionalization.     

Pore-scale modeling of dispersion in disordered porous media

We employ a direct pore-level model of incompressible flow that uses the modified moving particle semi-implicit (MMPS) method. The model is capable of simulating both unsteady- and steady-state flow directly in microtomography images of naturally-occurring porous media. We further develop this model to simulate solute transport in disordered porous media. The governing equations of flow and transport at the pore level, i.e., Navier-Stokes and convection-diffusion, are solved directly in the pore space mapped by microtomography techniques. Three naturally-occurring sandstones are studied in this work. We verify the accuracy of the model by comparing the computed longitudinal dispersion coefficients against the experimental data for a wide range of Peclet numbers, i.e., 5×10(-2)相似文献   

Evaluation of the in-situ aerobic cometabolism of chlorinated ethenes by toluene-utilizing microorganisms using push-pull tests

A series of transport, biostimulation, and activity push-pull tests were performed under induced and natural gradient conditions in a trichloroethene (TCE) and cis-dichloroethene (c-DCE) contaminated aquifer. Transport tests demonstrated the feasibility of injecting and recovering complex solute mixtures from the aquifer. During the biostimulation tests, decreases in toluene concentration and the production of o-cresol as an intermediate oxidation product indicated the presence of toluene-utilizing microorganisms. Activity tests demonstrated that the stimulated microbial community had the ability to transform injected c-DCE and trans-dichloroethene (t-DCE) at similar zero-order rates. Injected isobutene was oxidized to isobutene oxide, which indicated that a toluene ortho-monooxygenase enzyme system was likely responsible for the observed c-DCE and t-DCE transformations. c-DCE zero-order transformation rates in drift push-pull tests were similar to those obtained from traditional push-pull tests (about 0.1 microM/h). Analysis of drift test data using first-order kinetic analysis resulted in similar conclusions as those obtained using zero-order kinetic analyses. When 1-butyne, an inhibitor of toluene ortho-monooxygenase, was added to injected test solutions, the oxidation of toluene, and the transformation of isobutene, c-DCE, and t-DCE were inhibited. The results illustrate how a series of push-pull tests can be used in combination to detect, quantify and confirm in-situ cometabolic microbial transformations.     

Indoor/Outdoor relationships, trends, and carbonaceous content of fine particulate matter in retirement homes of the Los Angeles Basin

Hourly indoor and outdoor fine particulate matter (PM2.5), organic and elemental carbon (OC and EC, respectively), particle number (PN), ozone (O3), carbon monoxide (CO), and nitrogen oxide (NOx) concentrations were measured at two different retirement communities in the Los Angeles, CA, area as part of the Cardiovascular Health and Air Pollution Study. Site A (group 1 [G1]) was operated from July 6 to August 20, 2005 (phase 1 [P1]) and from October 19 to December 10, 2005 (P2), whereas site B (group 2 [G2]) was operated from August 24 to October 15, 2005 (P1), and from January 4 to February 18, 2006 (P2). Overall, the magnitude of indoor and outdoor measurements was similar, probably because of the major influence of outdoor sources on indoor particle and gas levels. However, G2 showed a substantial increase in indoor OC, PN, and PM2.5 between 6:00 and 9:00 a.m., probably from cooking. The contributions of primary and secondary OC (SOA) to measured outdoor OC were estimated from collected OC and EC concentrations using EC as a tracer of primary combustion-generated OC (i.e., "EC tracer method"). The study average outdoor SOA accounted for 40% of outdoor particulate OC (40-45% in the summer and 32-40% in the winter). Air exchange rates (hr(-1)) and infiltration factors (Finf; dimensionless) at each site were also determined. Estimated Finf and measured particle concentrations were then used in a single compartment mass balance model to assess the contributions of indoor and/or outdoor sources to measured indoor OC, EC, PM2.5, and PN. The average percentage contributions of indoor SOA of outdoor origin to measured indoor OC were approximately 35% (during G1P1 and G1P2) and approximately 45% (for G2P1 and G2P2). On average, 36% (G2P1) to 44% (G1P1) of measured indoor OC was composed of outdoor-generated primary OC.     

Separation and determination of trace levels of aromatic amines by HPLC

Aromatic amines were analysed by normal phase and reverse phase high performance liquid chromatography employing silica gel and octadecyl silane (ODS) columns, respectively. A number of mobile phases were used. The results obtained on silica gel column were compared with those achieved on reverse phase column. Excellent results were obtained on ODS and shoulder peaks were eliminated when a mixture of methyl alcohol and sodium perchlorate was used as mobile phase.     

Application of catastrophe loss modelling to promote property insurance in developing countries

Many mega cities in developing countries are exposed to the sources of natural catastrophes, particularly seismic activity. A high level of seismic hazard in some of these places, coupled with a relatively high degree of vulnerability within the built environment, can result in dire human and economic consequences. This paper contains examples of such potentially disruptive factors in relation to Tehran, Iran. It presents preliminary seismic loss estimates for residential buildings in a pilot area of northern Tehran. The paper briefly investigates the effectiveness of risk management measures and loss compensation mechanisms before assessing the feasibility of an insurance‐based risk transfer instrument for managing potential seismic losses among residential buildings in Tehran. It goes on to suggest how probabilistic catastrophe loss modelling can help local insurers to manage their portfolios and facilitate risk sharing among insurance companies and households. Finally, the paper addresses the question of how catastrophe loss modelling can help to strengthen the penetration of property insurance in developing countries.