Preparation of Graphene Oxide Composites and Assessment of Their Adsorption Properties for Lanthanum (III)

In this study, graphene oxide (GO) was prepared using the improved Hummers’ method, and GO was carboxylated and modified into hydroxylated graphene oxide (GOH). Diatomaceous earth (DE), which exhibits stable chemical properties, a large specific surface area, and high porosity, as well as chitosan/magnetic chitosan, was loaded by solution blending. Subsequently, carboxylated graphene oxide/diatomite/chitosan (GOH/DCS) and carboxylated graphene oxide/diatomite/magnetic chitosan (GOH/DMCS) composites were prepared through simple solid–liquid separation. The results showed that the modified GOH/DCS and GOH/DMCS composites could be used to remove lanthanum La(III)), which is a rare earth element. Different factors, such as initial solution concentration, pH of the solution, adsorbent dosage, adsorption contact time, and adsorption reaction temperature, on adsorption, were studied, and the adsorption mechanism was explored. An adsorption–desorption recycling experiment was also used to evaluate the recycling performance of the composite material. The results show that at the initial solution concentration of 50 mg·g−1, pH = 8.0, 3 g·L−1 adsorbent dosage, reaction temperature of 45 °C, and adsorption time of 50 min, the adsorption effect is the best. The adsorption process is more in line with the pseudo-second-order kinetic model and Langmuir model, and the internal diffusion is not the only controlling effect. The adsorption process is an endothermic and spontaneous chemical adsorption process. The maximum adsorption capacity of GOH/DMCS for La(III) at 308K is 302.51 mg/g through model simulation. After four adsorption–desorption cycles, the adsorption capacity of the GOH/DMCS composite for La(III) initially exceeded 74%. So, GOH/DMCS can be used as a reusable and efficient adsorbent.

Immobilization of Lead and Nickel Ions from Polluted Yam Peels Biomass Using Cement-Based Solidification/Stabilization Technique

Nowadays, biomass has been employed to prepare biosorbents for heavy metals uptake; however, further disposal of polluted material has limited its application. In this work, nickel and lead removal was performed using yam peels and the resulting polluted biomass was mixed with concrete to produce bricks. The biomass was characterized by FT-IR analysis for testing functional groups diversification before and after adsorption process. The effect of adsorbent dosage, temperature, and initial solution concentration was evaluated to select suitable values of these parameters. Adsorption results were adjusted to kinetic and isotherm models to determine adsorption mechanism. Desorption experiments were also performed to determine the appropriate desorbing agent as well as its concentration. Immobilization technique of cement-based solidification/stabilization was applied and the polluted biomass was incorporated to concrete bricks at 5 and 10%. Mechanical resistance and leaching tests were carried out to analyze the suitability of heavy metals immobilization. The suitable values for dosage, temperature, and initial solution concentration were 0.5 g/L, 40°C and 100 ppm, respectively. The kinetic model that best fitted experimental results was pseudo-second order indicating a dominant physicochemical interaction between the two phases. The highest desorption yields were found in 52.47 and 74.84% for nickel and lead ions. The concrete bricks exhibited compression resistance above 5 MPa and all the leachate reported concentrations below the environmental limit. These results suggested that nickel and lead immobilization using concrete bricks is a good alternative to meet disposal problems of contaminated biomass.

Removal of nitrate using activated carbon-based electrodes for capacitive deionization

The removal performance of nitrate using capacitive deionization (CDI) of activated carbon (AC)-based electrodes were studied. The AC electrode was prepared and the effect of cell voltage, flow rate and initial solution concentration on ion removal were investigated. Furthermore, the AC was modified with phosphoric acid (ACP) and the surface structure of AC and ACP were analyzed. The results showed that the specific surface area of AC increased by 10.71% after the modification. The mesopore ratio and micropore ratio increased by 14.69% and 24.06%, respectively. The optimal conditions of AC electrode was a voltage of 1.4 V and flow rate of 20 mL/min while the ACP electrode was a voltage of 1.4 V and flow rate of 10 mL/min. The electrosorption capacity of ACP electrode was improved and the unit of electrosorption load was high to 19.28 mg/L. For the AC or ACP electrode, the nitrate removal efficiency decreases with the increase in the initial feed solutions, but the unit electrosorption load gradually increased with the improvement of initial feed solutions' concentration and the ACP electrode was superior to the AC electrode. Therefore, the ACP electrode would be suitable for the application of CDI on the nitrate removal.

The Degradation of Organophosphorous Pesticide Wastewater by Sonophotocatalytic Oxidation Technology

Organophosphosphous pesticides wastewater was degradated by sonophotocatalytic oxidation technology,and some factors affecting sonophotocatalytic oxidation reaction were studied in details such as different degradation modes,the time of degradationinitial solution concentration initial pH valuethe amount of catalyst and the effect of Fenton,etc.In the end the optimal conditons were determined.The conclusion we drawed was that the optimal time of degradation was 100min initial solution concentration was 100mg/Lthe amount of catalyst AgBr/TiO2 was 0.6g,moreover the adding of Fenton could greatly enhance the degradation rate.

Degradating Organophosphosphous Pesticides Wastewater by Sonophotocatalytic Oxidation Technology

Organophosphosphous pesticides wastewater was degradated by sonophotocatalytic oxidation technology,and some factors affecting sonophotocatalytic oxidation reaction were studied in details such as different degradation modes,the time of degradation、initial solution concentration 、initial pH value、the amount of catalyst and the effect of Fenton,etc.In the end the optimal conditons were determined.The conclusion we drawed was that the optimal time of degradation was 100min 、initial solution concentration was 100mg／L、initial pH value was 7、the amount of catalyst was 0.6g,moreover the adding of Fenton could greatly enhance the degradation rate.

Ammonium Removal from Aqueous Solutions Using an Ammonium Ion-Exchange Material, the Equilibrium Study

This article investigates the removal of ammonium from aqueous solutions using the ammonium ion-exchange material prepared by the modified kaolin. Batch tests were performed under a range of conditions to assess the effect of initial solution concentration, contact time and solution PH on the performance and capacity of the media for this application. The findings show that increasing initial solution concentration and contact time provide the best performance at an optimum PH of between 6 and 7 and the maximum ammonium adsorption capacity reaches at 79mgNH4+g-1 under the experimental conditions studied. Five isotherm models were used to describe the isotherm data. Three-parameter isotherm models (Redlich–Peterson and Langmuir–Freundlich) prove a better fit than two-parameter isotherm models (Langmuir, Freundlich and Temkin). These results indicate that the ammonium ion-exchange material is a promising material for cost-effective removal of ammonium from wastewater.

Effects of NaCl and Na2SO4 on Growth and Solute Composition of Highbush Blueberry (Vaccinium corymbosum)

Hardwood cuttings from the field-grown blueberry cultivar Blue Crop were grown in nutrient solution with added NaCl(0-200 mol m-3) or Na2S04 (0-50 mol m-3). After 5 weeks' growth, leaf fresh weight was greater on either salt than on no salt, and was maximal at 20 mol m-3 NaCl or 25 mol m-3 Na2SO4. Leaf dry weight increased in proportion to external salinity for both salts. Leaf damage was severe at concentrations greater than 75 mol m-3 NaCl or 50 mol m-3 Na2SO4. In the presence of NaCl, Na+ and Cl- concentrations in the leaves were 3-4 times greater than initial solution concentration. Growth in the presence of NaCl was accompanied by loss of K+ in leaves (from 94 to 36 μmol g FW-1), stems (from 48 to 20 μmol g FW-1) and roots (from 88 to 12 μmol g FW-1). In the presence of Na2SO4, leaf Na+ concentration increased to 2-3 times greater than initial solution concentration. Na+ uptake and loss of K+ were less in plants grown on Na2SO4 than on NaCl solutions containing equimolar concentrations of sodium. In Na2SO4 solutions, SO42- in stems and roots accumulated approximately to initial external concentration. SO42- concentration in leaves was 1.5-2.0 greater than initial external levels. In plants grown in 20-50 mol m-3 NaCl, non-significant slight increases in the foliar concentrations of glycinebetaine, choline and proline were measured (maximum total of 8 μmol g FW-1 for all metabolites). However, sucrose (2-fold), glucose (3-fold), fructose (4-fold), sorbitol (4-fold) and malate (7-fold) concentrations were significantly enhanced. The total increase in concentration of all measured sugars was approximately 100 μmol g FW-1, while malate concentrations increased by approximately 15 μmol g FW-1. Our data suggest that blueberries are poor Na+ and Cl- excluders and appear to accumulate these ions in leaves. Although growth is enhanced initially on the levels of salt tested, and accumulation of ions and sugars is presumably sufficient for osmotic adjustment, leaf damage eventually occurs. This is probably due to the toxic effects of accumulated Na+ and Cl- in leaves and/or to the severe reduction of K+ levels.