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Uranium biosorption was investigated using the bio-adsorbent of Plantain leaves. First, the bio-adsorbent structure was characterized using BET, SEM, and FTIR. The effective parameters pH, initial uranium concentration, bio-adsorbent dose, and the temperature were investigated using a central composite design (CCD). Experimental data were analyzed using Design Expert 12.0.3.0 software. According to the obtained results, the pH value of 4, initial metal ion concentration of 10 mg L−1, the bio-adsorbent dose of 0.297 g, and the temperature of 25 °C were proven for maximum biosorption efficiency of U(VI) ions from aqueous solutions. The contact time was investigated to understand the type of kinetics of the reaction. The maximum biosorption efficiency was 90 min. The optimal biosorption efficiency was 92.69%. The Freundlich isotherm and pseudo-second-order models were the best isotherms and kinetic models fitted with the results of the studied bio-adsorbent, respectively.

The current study presents a simple and scalable method for the synthesis of (aminomethyl)phosphonic acid-functionalized graphene oxide (AMPA-GO) adsorbent. The chemical structure of the new material was disclosed by different instrumental analyses (e.g. FTIR, Raman, XPS, AFM, TEM, XRD, CHN, and UV), and two pertinent mechanisms namely nucleophilic substitution and condensation were suggested for its formation. Adsorption experiments revealed that both AMPA-GO and plain GO have a high affinity toward Th(IV) ions, but the AMPA-GO is superior in terms of adsorption capacity, rate of adsorption, selectivity, pH effect, etc. Indeed, the AMPA-GO can uptake Th(IV) nearly instantaneously, and coexisting Na+ions have no effect on its adsorption. Thanks to Langmuir isotherm, the maximum adsorption capacities of the GO and AMPA-GO were obtained 151.06 and 178.67 mg g−1, respectively. Interestingly, GO and AMPA-GO both showed a higher preference for thorium over uranium so that the average “Kd(Th)/Kd(U)” for them was 52 and 44, respectively. This data suggests that chromatographic separation of thorium and uranium is feasible by these adsorbents.

A continuous bulk liquid membrane technique “three-phase flow layered bulk liquid membrane (TPFLBLM)” is proposed. Aspects related to TPFLBLM were studied in thorium removal by D2EHPA as the carrier. The mass transfer coefficients were determined and experimental correlations were developed to determine the local mass transfer coefficients. The results showed that the thorium transport increases with increase in the membrane and acceptor phases flow rates. Based on the developed correlations, more than 90% Th(IV) transfer is achieved after 30 min of the TPFLBLM system continuous operation with a surface-to-volume ratio of 375 containing 600 mL acceptor phase, 42.5 mL organic phase, and 30 mL donor phase circulating with the flow rates of 300, 274 and 78 mL min−1, respectively.

The performance of the hollow fiber renewal liquid membrane (HFRLM) in the continuous and recycling modes for the extraction of uranium(VI) from the acidic sulfate solution has been investigated. Alamine 336 diluted in kerosene was used as a carrier in liquid membrane (LM) phase. In the batch experiments, the effects of sulfuric acid, extractant and uranium(VI) concentration were studied and the optimum concentration of the donor and LM phases were determined 0.15 mol L−1and 0.0125 mol L−1, respectively. Various parameters affecting the HFRLM performance including the lumen and shell side flow rate, organic/aqueous volume ratio, acceptor phase type and concentration of carrier and acceptor phase were studied. The mass transfer flux increases with increasing the lumen side flow rates and the shell side flow rate did not have any significant effect. The uranium transfer flux increases with increasing O/A ratio, acceptor and Alamine 336 concentration, and reaches a maximum value at 1/20, 0.5 mol L−1and 0.0125 mol L−1, respectively. Further increase in these parameters result in uranium transfer decrement. The results show that liquid membrane phase is a rate-controlling step. Among the investigated acceptor phases, 0.5 mol L−1NH4Cl result in 60.35% uranium(VI) recovery in the recycling mode.

Strontium (Sr) and Cesium (Cs) are two important nuclear fission products which are present in the radioactive wastewater resulting from nuclear power plants. They should be treated by considering environmental and economic aspects. In this study, artificial neural network (ANN) was implemented to evaluate the optimal experimental conditions in continuous electrodeionization method in order to achieve the highest removal percentage of Sr and Ce from aqueous solutions. Three control factors at three levels were tested in experiments for Sr and Cs: Feed concentration (10, 50 and 100 mg/L), flow rate (2.5, 3.75 and 5 mL/min) and voltage (5, 7.5 and 10 V). The obtained data from the experiments were used to train two ANNs. The three control factors were utilized as the inputs of ANNs and two quality responses were used as the outputs, separately (each ANN for one quality response). After training the ANNs, 1024 different control factor levels with various quality responses were predicted and finally the optimum control factor levels were obtained. Results demonstrated that the optimum levels of the control factors for maximum removing of Sr (97.6%) had an applied voltage of 10 V, a flow rate of 2.5 mL/min and a feed concentration of 10 mg/L. As for Cs (67.8%) they were 10 V, 2.55 mL/min and 50 mg/L, respectively.