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This study used excess sludge from a sewage treatment plant as raw material to extract humic acid (HA) and explore the ability of HA to adsorb Pb2+ from a solution. The effects of the adsorbent amount, solution pH, and co-existing cations on the adsorption process were investigated. The study showed that the humic acid derived from sludge (S-HA) surface had a loose, clustered texture. The S-HA surface contained many oxygen-containing functional groups, such as carboxyl groups, alcohol hydroxyl groups, and phenolic hydroxyl groups. The presence of co-existing cations, such as Na+, NH4+ and Ca2+, in the solution was not conducive to the adsorption of Pb2+ by S-HA. As the solution pH increased, the adsorption of Pb2+ by S-HA gradually increased. The process by which S-HA adsorbed Pb2+ conformed to a pseudo-second order kinetic model. Additionally, the overall adsorption rate was controlled by liquid membrane diffusion and intra-particle diffusion. The adsorption isotherm followed the Langmuir model, and the S-HA had a maximum adsorption capacity of 27.59 mg/g at 25 °C. The adsorption dynamics and thermodynamics results showed that the adsorption of Pb2+ by S-HA occurred via both physical adsorption and chemical adsorption processes.

For continuous and efficient oil/water separation and adsorption of dyes, coconut shell powder was grafted onto the surface of quartz sand by dip-coating method to make coconut shell powder-covered quartz sand filter media (CSQS) with superhydrophilic and underwater superoleophobic properties and superoleophilic and underoil highly hydrophobic properties. The contact angles of the underwater oil and underoil water with CSQS were more than 151.2&deg, and 134.2&deg, respectively. A continuous oil/water separation device was designed. The separation device filled with CSQS can separate oil/water mixture (whether heavy or light oil) into water and oil at the same time with a separation efficiency of above 99.92%. The filter layer can be recovered through reverse extrusion even after lyophobic liquid penetrated the filter layer, hence, the separation efficiency of the filter layer was still above 99.99% for diesel and water mixture. Simultaneously, CSQS can effectively adsorb methylene blue with the highest removal rate as 98.94%. CSQS can maintain stable wettability under harsh environment conditions. This paper provides a new idea on continuous and efficient oil/water separation and simultaneous dye adsorption.

Deep bed filtration is commonly used to remove oil from oily wastewater. The wettability of the filter media greatly influences the oil removal efficiency. A filter with a strong hydrophobicity and oleophilicity results in a higher oil removal efficiency. To improve the hydrophobicity and oleophilicity, ZnO nanoparticles and octadecyltrichlorosilane (OTS) were coated on quartz sand filter media. SEM, FTIR and XPS were used to study the morphology and chemical composition of the filters, and adsorption capacity and oil removal efficiency experiments were performed to assess the oil removal performance. The results show that the OTS molecules are grafted onto the surface of the quartz sand filter through chemical bonding, and the OTS/ZnO-coated quartz sand filter is superhydrophobic and oleophilic, with a water contact angle of 154.1° and an oil contact angle of 0°. The OTS/ZnO-coated quartz sand filter has very high mechanical stability and acid resistance. The oily wastewater treatment performance is greatly improved after application of the OTS/ZnO coating, and the superhydrophobic quartz sand filter media can potentially be used to filter oily wastewater and achieve high oil removal efficiency.

A water-soluble macromolecule flocculant was developed for the removal and recovery of Co(II) from water samples. The flocculant, called dithiocarboxyl polyethyleneimine (DTPEI), has the functions of chelation, precipitation, and flocculation for Co(II). The effects of settling time, hydraulic conditions, initial Co(II) concentration, pH value, coexisting common compounds, and turbidity on the removal of Co(II) by DTPEI were investigated through flocculation tests. DTPEI could effectively remove Co(II) for different initial concentrations of Co(II) in water samples, and the settling velocity of the flocs formed between DTPEI and Co(II) was very rapid. Because pH value may affect the Co(II) species, the protonation of the functional groups on DTPEI molecular chains, and the surface charge of the flocs, the removal rate of Co(II) would increase by raising pH from 2.0 to 7.8. The maximum removal rate of Co(II) reached 100% at pH 3.0–7.8. The presence of common compounds (KCl, NaCl, CaCl2, MgCl2, NaNO3, and Na2SO4) in water samples had less impact on the Co(II) removal. Furthermore, when the turbidity coexisted in the water samples containing Co(II), Co(II) and turbidity were simultaneously removed by DTPEI because of the adsorption bridging effect and the sweep function. The maximum removal rate of turbidity could reach 99.8%. However, the existence of turbidity inhibited the Co(II) removal due to the consumption of DTPEI for turbidity. Cobalt could be recovered from the flocs of DTPEI–Co by using acid solutions because DTPEI–Co may be decomposed in high-concentration acid solutions. The recovery of cobalt was 77.1% in 2.0 mol/L of HNO3 solution for soaking 72 h. The results of FTIR spectra indicate that the chelating reaction occurred between Co(II) and C( S) SH and NH2 on DTPEI molecular chains to form the DTPEI–Co flocs.

School of Environmental and Municipal Engineering, Lanzhou Jiaotong University, Lanzhou, Gansu, 730070, P. R. China E-mail : 36935112@qq.com Fax : 86-931-49560177 Manuscript received online 12 october 2016, accepted 13 December 2016 To precisely and accurately measure wettabilities by capillary rise, an improved expression for this rise that incorporates hydrostatic effects was theoretically derived. Ceramic sand was tested by measuring the weight of liquid in a packed bed of deionized water and cyclohexane. Excellent agreement between the lipophilic to hydrophilic ratio (LHR) values calculated from our improved expression and those obtained by the equilibrium method was observed, validating our expression and confirming the suitability of the experimental method for small particles. Therefore, it should be possible to accurately measure the wettability of small particles as well as that of porous materials.

In order to increase the oily wastewater treatment performance, the hydrophobicity of quartz sand filter medium was improved by surface modification using 3-aminopropyltriethoxy silane coupling agent (KH550). The interfacial interactions between quartz sand surface and KH550 as well as the wettability of quartz sand filter before and after surface modified were studied. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses showed that the silane coupling agent molecular binds strongly to quartz sand surface. Scanning electronic microscopy (SEM) observation showed that a thin layer was formed on the surface of modified quartz sand. Wettability study confirmed that the hydrophobicity of surface modified quartz sand was extremely increased than original quartz sand. The results indicate that the silane coupling agent play an important role in improving the hydrophobicity of quartz sand filter, and the oily wastewater treatment performance is greatly improved after surface modified.

Generally, increasing the hydrophobicity of filter media leads to enhanced oil removal by filtration. In this study, the hydrophobicity of quartz sand filter media was increased by modifying the particles with titanate and silane coupling agents (DN101 and KH550) by dry processing. The results show that the quartz sand particle surfaces were uniformly covered with the coupling agents after surface modification, and many fine particles were observed. The optimised parameters for the surface modification procedure were a DN101:KH550 ratio of 1:2, total coupling agent amount of 1.0 wt%, reaction temperature of 60 °C and reaction time of 50 min. Under these conditions, the water contact angle on the filter media surface increased from 40.1° to 82.9°, and the effluent oil concentration decreased from 4.74 mg/L for the unmodified filter media to 2.99 mg/L for the modified filter media when the influent oil concentration was 17.3 mg/L. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy results show that DN101 and KH550 formed chemical bonds with the quartz sand surface groups, resulting in the formation of a uniform, stable coating on the surface.