Kaolinite clay obtained from Longyan, Chinawas investigated to remove heavymetal ions fromwastewater. Thus,the present study includes the adsorption of Pb (II), Cd (II), Ni (II) and Cu (II) in aqueous solution on kaolinite clay through the process of adsorption under various conditions (with variable concentration ofmetal ion, amount of clay, pH and mixing time). Increasing pH favours the removal of metal ions till they are precipitated as the insoluble hydroxides. The uptake is rapid with maximumadsorption being observed within 30 min for Pb (II), Cd (II), Ni (II) and Cu (II). In addition, the results obtained fromadsorption isothermindicated that these data can be better fittedwith the Freundlich equation than the Langmuir equation. Furthermore, the XRD patterns confirmed that this kaolinite clay sample ismainly a mixture of kaolinite and illite clays. The SEMimages of samples showed irregular surface morphology. Finally, this kaolinite clay was used for removing metal ions fromrealwastewater such as Pb (II), where its concentration was reduced from 160.00 to 8.00mg/L.

Bentonite-supported nanoscale zero-valentiron (B-nZVI) was synthesized using liquidphase reduction. The orthogonal method was used to evaluate the factors impacting Cr(VI) removal and this showed that the initial concentration of Cr(VI), pH, temperature, and B-nZVI loading were all importance factors. Characterization with scanning electron microscopy (SEM) validated the hypothesis that the presence of bentonite led to a decrease in aggregation of iron nanoparticles and a corresponding increase in the specific surface area (SSA) of the iron particles. B-nZVI with a 50% bentonite mass fraction had a SSA of 39.94m2/g, while the SSA of nZVI and bentonite was 54.04 and 6.03 m2/g, respectively. X-ray diffraction (XRD) confirmed the existence of Fe0 before the reaction and the presence of Fe (II), Fe(III) and Cr(III) after the reaction. Batch experiments revealed that the removal of Cr (VI) using B-nZVI was consistent with pseudo first-order reaction kinetics. Finally, B-nZVI was used to remediate electroplating wastewater with removal efficiencies for Cr, Pb and Cu > 90%. Reuse of B-nZVI after washing with ethylenediaminetetraacetic acid (EDTA) solution was possible but the capacity of B-nZVI for Cr(VI) removal decreased by approximately 70%.

In this study, organobentonites were prepared by modification of bentonite with various cationic surfactants, and were used to remove As(V) and As(III) from aqueous solution. The results showed that the adsorption capacities of bentonite modified with octadecyl benzyl dimethyl ammonium (SMB3) were 0.288 mg/g for As(V) and 0.102 mg/g for As(III), which were much higher compared to 0.043 and 0.036 mg/g of un-modified bentonite (UB). The adsorption kinetics were fitted well with the pseudosecond-order model with rate constants of 46.7×10−3 g/mg h for As(V) and 3.1×10−3 g/mg h for As(III), respectively. The maximum adsorption capacity of As(V) derived from the Langmuir equation reached as high as 1.48 mg/g, while the maximum adsorption capacity of As(III) was 0.82 mg/g. The adsorption of As(V) and As(III) was strongly dependent on solution pH. Addition of anions did not impact on As(III) adsorption, while they clearly suppressed adsorption of As(V). In addition, this study also showed that desorbed rates were 74.61% for As(V) and 30.32% for As(III), respectively, after regeneration of SMB3 in 0.1M HCl solution. Furthermore, in order to interpret the proposed absorption mechanism, both SMB3 andUBwere extensively characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses.

phase liquid chromatography with UV detection is of limited applicability in the separation and identification of carboxylic acids because of the column's poor separation efficiency and the non-selective nature of the UV detector. To address this issue, RP-LC with electrospray ionization mass spectrometry has been explored for the confirmation and determination of carboxylic acids in plant root exudates, with ESI-MS providing structural information, high selectivity, and high sensitivity. The separation of 10 carboxylic acids (pyruvic, lactic, malonic, maleic, fumaric, succinic, malic, tartaric, trans-aconitic, and citric acid) was performed on a C18 column using an eluent containing 0.1% (v/v) acetic acid within 10 min, where the acidic eluent not only suppressed the ionization of the carboxylic acids to be retained on the column, but was also compatible with ESI-MS detection. In addition, an additional standard was used to overcome the matrix effect. The results showed that peak areas correlated linearly with the concentration of carboxylic acids over the range 0.05-10mg/L. The detection limits of target acids (signal-to-noise S/N ratio of 3) ranged from 20 to 30lg/L. Finally, the proposed method was used for the confirmation and determination of low-molecular-weight carboxylic acids in plant root exudates, and provided a simple analytical procedure, including sample processing, fast separation, and high specificity and sensitivity.

Bacterial strains isolated from oil refining wastewater sludge (Fuzhou, China) were used to biodegrade naphthalene in cultured medium. Bacillus fusiformis (BFN) strain was identified using 16S rDNA gene sequence analysis. Optimal conditions for the biodegradation of naphthalene included: temperature of 30℃, pH 7.0, 0.2% inoculum size and a C/N ratio of 1.0. Under these conditions and initial naphthalene concentration of 50mg/L, more than 99.1% was removed within 96h. Of those factors influencing the biodegradation of naphthalene, salinity and inoculum concentration were of greatest importance. Furthermore, the biodegradation kinetics of naphthalene corresponded with the first-order rate model. Degradation metabolites identified using GC-MS, included o-phthalic acid and benzoic acid, suggesting possible metabolic pathways. Finally, given these metabolites are water-soluble and non-toxic, the findings suggest a potential bioremediation role of Bacillus fusiformis (BFN) in the removal of naphthalene from wastewaters.

Nanoscale zero-valent iron (nZVI) used to remediate contaminated groundwater is limited due its lack of durability and mechanical strength. To address these issues, synthesized kaolin supported nanoscale zerovalent iron (K-nZVI) was used to remove Pb (II) ion from aqueous solution. This study has demonstrated that synthesized K-nZVI was efficient in removing Pb (II) from aqueous solution containing 500mgL−1 of Pb (II), where 90.1% of Pb (II) was removed within 60 min using 5g L−1 of K-nZVI having a nZVI mass fraction of 20% at pH 5-6. Ni (II) and Cd (II), as co-existent ions, were also removed by the synthesized KnZVI. This however had little effect on the removal of Pb (II) from solution. The synthesized K-nZVI could be reused more than 5 times when applied to remove Pb (II) from solution with concentrations of 50mgL−1. Additionally, synthesized K-nZVI was efficient in removing Pb (II) (98.8%) and total Cr (99.8%) from an electroplating wastewater, indicating that the synthesized nZVI is a potential remediation material when used for the treatment of electroplating wastewater containing metal ions.

Bentonite-supported nanoscale zero-valent iron (B-nZVI) was synthesized using liquidphase reduction. The orthogonal method was used to evaluate the factors impacting Cr (VI) removal and this showed that the initial concentration of Cr (VI), pH, temperature, and B-nZVI loading were all importance factors. Characterization with scanning electron microscopy (SEM) validated the hypothesis that the presence of bentonite led to a decrease in aggregation of iron nanoparticles and a corresponding increase in the specific surface area (SSA) of the iron particles. B-nZVI with a 50% bentonite mass fraction had a SSA of 39. 94m2/g, while the SSA of nZVI and bentonite was 54. 04 and 6. 03 m2/g, respectively. X-ray diffraction (XRD) confirmed the existence of Fe0 before the reaction and the presence of Fe (II), Fe (III) and Cr (III) after the reaction. Batch experiments revealed that the removal of Cr (VI) using B-nZVI was consistent with pseudo first-order reaction kinetics. Finally, B-nZVI was used to remediate electroplating wastewater with removal efficiencies for Cr, Pb and Cu>90%. Reuse of B-nZVI after washing with ethylenediaminetetraacetic acid (EDTA) solution was possible but the capacity of B-nZVI for Cr (VI) removal decreased by approximately 70%.

Adsorption of cationic methylene blue and anionic orange II onto unmodified and surfactant-modified zeolites was studied using a batch equilibration method. The effects of equilibrium time, solution pH, and sorption temperature were examined. The results suggested that 2% sodium dodecyl benzenesulfonate (SDBS)- and 3% sodium dodecyl sulfate (SDS)-modified zeolites had higher adsorption capacities for methylene blue than the unmodified zeolite, while 2% cetylpyridinium bromide hexadecyl (CPB)- and 2% hexadecylammonium bromide (HDTMA)-modified zeolites were the best adsorbents for orange II. The adsorption conditions were optimized, and the mechanisms of adsorption are briefly discussed.

A dried Azolla filiculoides (A. filiculoides ) biomass was used to remove Basic Orange (BO) dye from aqueous solution using batch experiments. The kinetic results demonstrated that the biosorption of BO onto the dried A. filiculoides was well described by the seudo-second-order kinetic model. The maximum biosorption capacity for BO was 833.33mg/g based on the Langmuir equation at a temperature of 303 K, a solution pH of 7.0, a biosorbent dosage of 5g/L and a contact time of 4h. From the D-R isotherm equation, mean free energy was calculated to be 8.69 kJ/mol at 303K, suggesting that the biosorption of BO onto the dried A. filiculoide involved chemisorption. The thermodynamic values, including ΔG, ΔH and ΔS obtained from the calculation, suggest that the biosorption of BO on the dried A. filiculoides biomass is feasible, spontaneous and endothermic under the experimental conditions in this study. Fourier transform infrared (FT-IR) spectroscopy was used to examine functional groups that may participate in the interaction between BO and dried A. filiculoides biomass. Results showed that the amino, carboxyl, and hydroxyl groups may be responsible for the biosorption of BO on the biomass.