The competitive adsorption of organic pollutants—phenol, aniline and n-heptane—from biologically treated coking wastewater on powdered activated carbon (PAC) was studied. Firstly, batch adsorption experiments of coking wastewater were conducted to investigate the effect of pH and temperature on their adsorption. Results showed that long-chain alkanes, benzoic, halogenated and phenolic compounds were adsorbed well under acidic condition, while amines were adsorbed well under alkaline condition; maximum co-adsorption amount of all kinds of organic compounds occurred at around pH 5. Then, Lagergren kinetic model and pseudo-second-order kinetic model were used to describe the adsorption process of phenol and aniline on PAC. The data were fitted very well with pseudo-second-order kinetics, and the adsorption capacity decreased with an increase in temperature, belonging to Freundlich multi-layer physical adsorption. The adsorption speed and capacity of phenol were superior to aniline in unitary and binary solution. The adsorption amount of n-heptane decreased by 26.6 % from ternary competitive absorption system of phenol, aniline and n-heptane compared with that in unitary solutions, which showed that phenol and aniline caused spatial adsorption steric hindrance to n-heptane.

Metaldehyde is a selective molluscicide used in the agricultural and residential sector to control slugs and snails for a wide variety of crops. In recent years, some water companies have started monitoring drinking water supply catchments for presence of this compound, with positive and concern results. Conventional techniques are yet to achieve complete efficient and feasible removal of metaldehyde. The aim of this study was to measure the efficiency of nano-sized zinc oxide/laponite composites (NZnC) in the effective removal of metaldehyde (influent concentration of 500 μg dm⁻³) through the interaction of photocatalysis. Reaction time, pH of sample solution and NZnC mass were tested against each other using a rotatable central composite design method of experimentation. Statistical tests showed that linear effects of time, quadratic/linear effects of NZnC mass and the interaction of pH and NZnC mass proved to be the most significant variables for degrading metaldehyde. Optimal values of each variable for the highest removal efficiency were achieved, being pH equal to 10.4 and NZnC mass added equal to 28 g. The rate of reaction was then predicted by non-linear regression of four models. The best fit was provided by the modified first-order with residual kinetic model, with the apparent degradation coefficient k equal to 0.0363 min⁻¹ and the lowest remaining metaldehyde concentration observed among all runs was 278.7 μg dm⁻³. NZnC has shown to be a prominent nanotechnology for metaldehyde removal.

This study aimed to evaluate the efficacy of using the byproduct of Moringa oleifera Lam. seeds as an adsorbent for removal of cadmium (Cd) from contaminated water. The material characterization was performed by scanning electron microscopy, infrared spectroscopy, and point of zero charge. The effects of the adsorbent mass, solution pH, contact time, and temperature were evaluated. In the preliminary studies, the mass of adsorbent (200–1200 mg) and pH conditions (5.0, 6.0, and 7.0) were varied. The time studies were performed at 20–180 min and the temperature studies at the range of 25–65 °C. The optimal conditions of adsorption obtained were 400 mg of adsorbent mass, 7.0 pH, and 160 min contact time with the adsorbent. The isotherms of adsorption were linearized according to Langmuir, Freundlich, and Dubinin–Radushkevich (D-R) models. The results showed better fit by the Freundlich and D-R models for Cd adsorption, describing a multilayer adsorption and, according to the value of the sorption energy (E), it has chemical nature. The maximum capacity of adsorption (Q ₘ) obtained was 7.864 mg g⁻¹. For a comparative study, the activated carbon (P.A.) was used applying the same optimal conditions used in the adsorption isotherms and desorption process for the biosorbent, obtaining a Q ₘ as 32.884 mg g⁻¹. The average desorption percentage showed that adsorbents have strong interaction with the metal. Based on these results, it was concluded that the biosorbent was effective in remediation of solutions containing Cd and thus the use of this alternative material is a viable option, since it has low cost and it is a byproduct which has not undergone previous treatment.

Adsorption of fluoroquinolone antibiotics using sludge-derived biochar made of various wastewater sludges was investigated. The sludge-derived biochar had relatively large Brunauer–Emmet–Teller specific surface areas that were beyond 110.0 m² g⁻¹ except the biochar made from the sludge collected from traditional sludge drying bed. The mesopore capacity was more than 57 % of the total pore capacity of all sludge-derived biochar except that made from the sludge dried through traditional sludge drying bed technique. High adsorption capacity of sludge-derived biochar was observed with a highest adsorption capacity of 19.80 ± 0.40 mg g⁻¹. High correlation between the adsorption capacity of sludge-derived biochar and the volatile content in the sludge source was observed. The Freundlich model (r ² values were in the range of 0.961–0.998) yielded the best fit with the experimental data of all the produced biochar. Fluoroquinolone antibiotics were readily adsorbed onto sludge-derived biochar. These findings suggest a new approach for the pollution control of fluoroquinolone antibiotics using low-cost sludge-derived biochar.

The evaluation of the contribution of natural sources to PM₁₀ and PM₂.₅ concentrations is a priority especially for the countries of European south strongly influenced by Saharan dust transport events. Daily PM₂.₅ concentrations and composition were monitored at an urban site at 14 m above ground level, at the National Technical University of Athens campus from February to December 2010. The typical dust constituents Si, Al, Fe, K, Ca, Mg, and Ti were determined by wavelength dispersive X-ray fluorescence spectrometry (WDXRF). Sulfur, a tracer of anthropogenic origin and major constituent of PM₂.₅, was determined by both WDXRF and ionic chromatography. The contribution of dust and sulfates in PM₂.₅ was calculated from the analytical determinations. An annual mean of 20 μg/m³ was calculated from the mean daily PM₂.₅ concentrations data. Twenty-two per cent of daily concentrations of PM₂.₅ reached or exceeded the EU annual target concentration of 25 μg/m³. The exceedances occurred during 13 short periods of 1–4 days. Back-trajectory analysis was performed for these periods in order to identify the air masses origin. From these periods, ten periods were associated to Saharan dust transport events. The most intense dust transport event occurred between February 17th and 20th and was responsible for the highest recorded PM₂.₅ concentration of 100 μg/m³ where the dust contribution in PM₂.₅ reached 96 %. The other dust transport events were less intense and corresponded to less pronounced enhancements of PM₂.₅ concentrations, and their contribution ranged from 15 to 39 % in PM₂.₅ concentrations. Air masses originated from northwest Africa while the influence of central Sahara was quite smaller.

Radionuclide and heavy metal contamination influences the composition and diversity of bacterial communities, thus adversely affecting their ecological role in impacted environments. Bacterial communities from uranium and heavy metal-contaminated soil environments and mine waste piles were analyzed using 16S rRNA gene retrieval. A total of 498 clones were selected, and their 16S rDNA amplicons were analyzed by restriction fragment length polymorphism, which suggested a total of 220 different phylotypes. The phylogenetic analysis revealed Proteobacteria, Acidobacteria, and Bacteroidetes as the most common bacterial taxa for the three sites of interest. Around 20-30 % of the 16S rDNA sequences derived from soil environments were identified as Proteobacteria, which increased up to 76 % (mostly Gammaproteobacteria) in bacterial communities inhabiting the mine waste pile. Acidobacteria, known to be common soil inhabitants, dominated in less contaminated environments, while Bacteroidetes were more abundant in highly contaminated environments regardless of the type of substratum (soil or excavated gravel material). Some of the sequences affiliated with Verrucomicrobia, Actinobacteria, Chloroflexi, Planctomycetes, and Candidate division OP10 were site specific. The relationship between the level of contamination and the rate of bacterial diversity was not linear; however, the bacterial diversity was generally higher in soil environments than in the mine waste pile. It was concluded that the diversity of the bacterial communities sampled was influenced by both the degree of uranium and heavy metal contamination and the site-specific conditions. © 2013 Springer Science+Business Media Dordrecht.

Imperata cylindrica leaf was used as raw material to prepare two different adsorbents through chemical modification by using sulfuric acid and phosphoric acid. These two adsorbents, sulfuric acid-modified I. cylindrica leaf-based adsorbent (SIC) and phosphoric acid-modified I. cylindrica leaf-based adsorbent (PIC), were used to adsorb nickel ions (Ni²⁺) from aqueous solutions. The I. cylindrica leaf-based adsorbent and modified I. cylindrica leaf-based adsorbents were characterized by Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). Different operational parameters such as initial solution pH, adsorbent size, adsorbent dosage, initial Ni²⁺ ion concentration, and temperature were studied. The adsorption isotherm and the adsorption kinetics were studied systematically. Based on the FT-IR spectrum before and after adsorption of Ni²⁺ ions, the adsorption mechanism involved both ion exchange and complexation between Ni²⁺ ions and functional groups on the surface of adsorbents. There was no sulfur and phosphorus detected in the aqueous solutions after adsorption. Therefore, SIC and PIC are effective in adsorbing Ni²⁺ ions and will not cause secondary pollution to the environment.

In this study, arsenate removal by apricot stone-based activated carbon (IAC) modified with iron (oxy-hydr)oxides was carried out. For this purpose, hybrid adsorbents based on Fe²⁺-loaded activated carbon (IAC–Fe(II)) and Fe³⁺-loaded activated carbon (IAC–Fe(III)) were synthesized by precipitation method. A three-level, three-factor Box–Behnken experimental design combined with response surface methodology (RSM) was employed to find the optimum combination of process parameters for maximizing the As(V) adsorption capacity of activated carbon-based iron-containing hybrid adsorbent. Three important operation parameters, namely, initial pH of solution (3.0–7.0), temperature (25–65 °C), and initial As(V) concentration (0.5–8.5 mg L⁻¹), were chosen as the independent variables, while the As(V) adsorption capacities of hybrid adsorbents were designated as dependent variables. Lack of fit test showed that the quadratic model provided the best fit to experimental data for both adsorbents with the highest coefficients of determination (R ²), adjusted R ², and p-values for lack of fit. The standardized effects of the independent variables and their interactions were tested by analysis of variance and Pareto chart. The model F-values (F IAC–Fₑ₍II₎=330.39 and F IAC–Fₑ₍III₎=36.19) and R ² values (R ² IAC–Fₑ₍II₎=0.9977 and R ² IAC–Fₑ₍III₎=0.9789) of second-order polynomial regression equations indicated the significance of the regression models. Optimum process conditions for As(V) adsorption onto IAC–Fe(II) were 63.68 °C, pH 3.10, and 8.4 mg L⁻¹ initial arsenic concentration, while 25.22 °C, pH 3.07, and 8.28 mg L⁻¹ initial As(V) concentration were found to be optimum conditions for IAC–Fe(III).

Quality of the essential commodity, water, is being compromised by contaminants originating from anthropogenic sources, industrial activities, agriculture, etc. Water scarcity and severe droughts in many regions of the world also represent a significant challenge to availability of this resource. Domestic rainwater harvesting, which involves collection and storage of water from rooftops and diverse surfaces, is successfully implemented worldwide as a sustainable water supplement. This review focuses on chemical and microbial qualities of domestic rainwater harvesting, with a particular focus on sources of chemical pollution and major pathogens associated with the water source. Incidences of disease linked to consumption and utilization of harvested rainwater are also discussed. In addition, various procedures and methods used for disinfection and treatment of harvested rainwater, such as implementation of filter systems (activated carbon, slow sand filtration, etc.), heat treatment, and chlorination, among others, are also presented.

We investigated the influence of immobilization of bacterial cells and photocatalytic material TiO2 on the degradation of phenol by conducting batch microcosm studies consisting of suspended, immobilized cells and immobilized TiO2 at various initial phenol concentrations (50-1,000 mg L-1). Results showed that both suspended and immobilized cells were concentration-dependent, exhibiting the increasing degradation rate with the concentration of up to 500 mg L-1 above which it declined. The degradation rate of 0.39-3.47 mg L-1 h-1 by suspended cells was comparable with those of the literature. Comparison of the degradation rates between suspended, immobilized cells and immobilized TiO2 revealed that immobilized cells achieved the highest degradation rate followed by immobilized TiO2 and suspended cells due to the toxicity of phenol at the high concentration of 1,000 mg L-1. This indicates that immobilization of bacterial cells or photocatalytic materials can serve a better alternative to offer the higher degradation efficiency at high phenol concentrations. © 2013 Springer Science+Business Media Dordrecht.