Search

Solid waste landfill (SWL) is known as a major pollution source contaminating air, water sources, and soil environment. The main hazard of SWL is leachate including high organic matter and nutrients. Recently, sulphate radical-based advanced oxidation processes (SR-AOPs) based on persulphate (PS) have been applied as a useful method for removal of chemical oxygen demand (COD) and ammonia from landfill leachate (LL). The removal efficiency of the SR-AOPs depends on effective parameters such as pH, oxidant dosage, catalyst dosage, temperature, reaction time, and so forth. Among SR-AOPs, thermal persulphate oxidation (TPO) seems to be promising for removal of both COD and ammonia; however, the high amount of energy cost is regarded as a major drawback. The drawbacks and future challenges for the use of SR-AOPs for LL have been discussed, and some strategies such as using coupled mechanisms of SR-AOPs have been proposed to tackle the common difficulties. Finally, the performance of SR-AOPs for treatment of LL has been compared with hydroxyl radical processes. [ABSTRACT FROM AUTHOR]

In this study, regeneration of DCF-spent activated carbon by microwave (MW) activated persulphate (PS), (MW+PS) and PS alone was investigated. The regeneration processes were optimised to achieve high adsorptive capacity with low operating cost, simultaneously. Optimisation was carried out with Taguchi L9 experimental design. Optimum conditions determined for (MW+PS) process were found as PS dose of 0.3 g, MW power of 406 W, the regeneration time of 8 min and pH of 7, while the optimum conditions determined for PS processes were found as PS dose of 1.5 g PS, the regeneration time of 15 min and pH of 9. At optimum conditions, an adsorptive capacity of 9.8 mg DCF/g GAC with an operating cost of 0.020 €/g GAC and an adsorptive capacity of 5.0 mg DCF/g GAC with an operating cost of 0.077 €/g GAC were found for (MW+PS) and PS processes, respectively. ANOVA analysis found that the most effective parameter to the responses for both regeneration processes was the PS dose, and its effect was 43.5% and 72.5% for (MW+PS) and PS processes, respectively. The regenerated GAC after at least 6 regeneration cycles was found to have a capacity above the adsorptive capacity of the raw GAC. [ABSTRACT FROM AUTHOR]

In this work, uranium(VI) sorption from aqueous sulphate medium using tri-n-octylamine impregnated Siplite LX-16 resin has been investigated using batch experiments. The sorption parameters including aqueous pH, initial U(VI) concentration, aqueous solution volume to impregnated resin weight (v/w) ratio, contact time and the sorption temperature have been studied. The experimental data have been examined by both equilibrium isotherms and kinetic sorption models. It was found that, the sorption process of U(VI) onto the working resin follows both Langmuir and Freundlich isotherms and quite agrees with the pseudo-second order and intraparticle diffusion models. [ABSTRACT FROM AUTHOR]

The sorption characteristics of uranium onto a strongly basic anion exchanger, Purolite A400, were investigated. The characteristics of Purolite A400, before and after sorption of uranium, were determined using scanning electron microscopy (SEM) and energetic-dispersive X-ray (EDX). The influence of the different parameters, which may affect the process of uranium sorption process, had been tracked. Specifically, impacts of initial uranium concentration, pH, contact time and temperature, on uranium removal, were studied. In addition, the sorption kinetics and equilibrium parameters were assessed. At the optimum conditions, the adsorption capacity of uranium was found to be nearly 117.6 mg/g. The kinetics and isotherm studies could show that the uranium sorption onto Purolite A400 is following the models of pseudo-second-order and Langmuir isotherm respectively. The thermodynamic parameters had indicated that the adsorption of uranium is an exothermic and spontaneous process. The detected results of uranium sorption could reveal that Purolite A400 is a suitable material for pre-concentration of uranium (VI) species from sulfate leach liquor. [ABSTRACT FROM AUTHOR]

Acid mine drainage (AMD) causes serious environmental issues once present in the food chain directly affects human health due to its high acidity, the presence of heavy metals and sulphate compounds. For this reason, the constant search for new technologies for the treatment of AMD is becoming increasingly necessary. This review aims to highlight the characteristics and damage caused by AMD and the main treatment approaches. With special emphasis on anaerobic bioreactors containing sulphate-reducing bacteria (SRB) as a sustainable and economical alternative for the treatment of this type of effluent, due to the ability of microorganisms to use toxic metals in their metabolism, besides generating alkalinity in the environment and neutralising acidic compounds. SRB metabolise the electron donor and the sulphate ion, generating hydrogen sulphide and carbonic acid. In this way, future perspectives and major advances involving the treatment of this wastewater through microorganisms were addressed. [ABSTRACT FROM AUTHOR]