Super adsorbent - based remediation and on-site flow injection analysis determeniation of arsenic ions in gold mining site

Arsenic is a mineral which is abundant in gold mining sites. It is a toxic substance which needs to be removed. Thus, this research investigated the problem of extremely high arsenic (As) concentration in effluent (water and slurry) from Selinsing gold mine site, Pahang, Malaysia and developed an effective operational remedial method using an adsorbent material (Ecomel). In this research, a new method for measuring As(III) and As(V), which exist in the contaminated soil and liquid effluents was developed using flow injection analysis (FIA) system, while the total As was analyzed using atomic fluorescence spectrometry (AFS) for the remediating samples. By using the FIA method, the As speciation detection limit of (S/N = 3) for both As(III) and As(V) were found to be 5 μg/L with standard deviation 2.2 (n = 20). It also showed a wide dynamic range coefficient of detection (R2) of 0.999 for As(III) and 0.9989 for As(V). This portable analytical method was successfully applied for the determination of As speciation in the effluent collected from Selinsing gold mine site without further treatment. For the characterizations of slurry and adsorbent materials (Ecomel), X-ray diffraction (XRD), X-ray fluorescence (XRF), energy-dispersive X-ray spectroscopy (EDX), Field Emission Scanning Electron Microscopy (FESEM), Focus Ion Beam–Scanning Electron Microscope (FIB-SEM), Inductively Coupled Plasma Optical Emission Spectrophotometer (ICPOES), Elemental Analyzer (EA) and Brunauer–Emmett– Teller (BET) were used. In the case of liquid effluent from the tailing dam, the pH and cyanide concentrations were measured at 11.5 and 204 mg/L, respectively. However, the batch experiments clearly proved that As leaching from the slurry (contact time: 24 h, stirring speed: 200 rpm, and S:L ratio 1:5) was extremely higher at pH 11.5 compared to pH 2.5 and were measured to be 8,720 and 1,010 μg/L, respectively. The major contributors to the exceedingly elevated levels of As concentration in liquid effluents were attributed to alkaline pH, high cyanide and silicate concentration, as well as high oxidation environment. The batch experiments on Ecomel revealed that maximum adsorption capacity determined at initial pH 2.5 from the Langmuir-Freundlich isotherm model was found to be 704.7 and 122.7 mg/g for As(III) and As(V), respectively. These results indicated that Ecomel has high adsorbent efficiency, cost-effective and is suitable for in-situ and ex-situ remediation of highly concentrated As(III) and As(V) toxicants in aqueous solutions. For As standard solution with initial pH 2.5 and concentration of As at 1 mg/L, it was observed that 0.3125 g/L of Ecomel with 2 h contact time can adequately remove 97.0% of As(V) and 98.1% of As(III), respectively. As a conclusion, results from AFS showed that the treatment of As using Ecomel at initial pH 2.5 was the most proficient for remediation of liquid effluent and slurry

Synthesis and characterization of Cu(OH)2-NWs-PVA-AC Nano-composite and its use as an efficient adsorbent for removal of methylene blue

The present study focused on the synthesis of copper hydroxide nanowires decorated on activated carbon (Cu(OH)2-NWs-PVA-AC). The obtained Cu(OH)2-NWs-PVA-AC Nano-composite was distinguished by XRD, SEM, EDX, BET, FTIR and XPS respectively. Besides, different variables such as solution pH, and initial dye concentration, contact time, and temperature were performed on the adsorption efficiency of MB in a small batch reactor. Further, the experimental results are analyzed by various kinetic models via PFO, PSO, intra-particle diffusion and Elovich models, and the results revealed that among the kinetic models, PSO shows more suitability. In addition, different adsorption isotherms were applied to the obtained experimental data and found that Langmuir–Freundlich and Langmuir isotherm were best fits with the maximum adsorption capacity of 139.9 and 107.6 mg/g, respectively. The Nano-composite has outstanding MB removal efficiency of 94–98.5% with a span of 10 min. and decent adsorption of about 98.5% at a pH of 10. Thermodynamic constants like Gibbs free energy, entropy, and enthalpy were analyzed from the temperature reliance. The results reveal the adsorption processes are spontaneous and exothermic in nature. The high negative value of ?G° (- 44.11 to - 48.86 kJ/mol) and a low negative value of ?H° (- 28.96 kJ/mol) show the feasibility and exothermic nature of the adsorption process. The synthesized dye was found to be an efficient adsorbent for the potential removal of cationic dye (methylene blue) from wastewater within a short time

Synthesis of copper oxide nanowires-activated carbon (AC@CuO-NWs) and applied for removal methylene blue from aqueous solution: kinetics, isotherms, and thermodynamics

In the present study, we focused on the synthesis of copper oxide nanowires decorated on activated carbon (AC@CuO-NWs) for the removal of methylene blue (MB) from aqueous solutions. The AC@CuO-NWs nanocomposite is synthesized via simple precipitation method and characterized by using various techniques which includes scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), and X-rays diffraction analysis (XRD). XRD results confirmed the monoclinic structure of CuO-NWs with the average crystalline size ~ 17.48 nm. The SEM images indicated the wire-like structure and EDX analysis confirms the CuO nanomaterial. The SEM image shows that nanowires are agglomerated to form like flower shape. The batch adsorption experiments were optimized using various parameters such as pH, contact time, initial dye concentration, kinetic and isotherm studies. The results showed that the adsorption processes were well fitted with the PSO model. The adsorption equilibrium experimental data fitted to the Langmuir models with a maximum adsorption capacity of 141.73 mg/g at 328 K. The thermodynamics results reveal that the adsorption processes are spontaneous and endothermic in nature. The high negative value of ΔG° and a low value of ΔH° show the feasibility with physisorption and endothermic nature of the adsorption process. The acquire results indicating that AC@CuO-NWs based nanocomposite is having the high MB adsorption capacity in short equilibrium period and good substitute as the low-cost adsorbent in wastewater treatment. The synthesis of AC@CuO-NWs nanocomposite material is simple, easy and scale-up that might be efficiently used in water treatment technologies

Adsorption of acid blue 25 from aqueous solution using zeolite and surfactant modified zeolite

In the present study, we have demonstrated the Indonesian natural zeolite and modified zeolite was used to remove the acid blue 25 (AB25) from wastewater. The adsorption capacity of AB25 on zeolite and modified zeolite (zeolite-CTAB) were investigated by various batch adsorption experiments. The modification effect on the surface of zeolite was analyzed using Fourier transforms infrared spectra, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray fluorescence, and X-ray diffraction, respectively. The maximum removal of AB25 was obtained under acidic conditions at pH 2. The kinetic experimental results imply that the adsorption of AB25 onto these adsorbents well followed the second-order kinetic model. The maximum adsorption capacity of 64.2 mg/g was found in Zeolite at 30°C and 112.44 mg/g for zeolite-CTAB at 60°C. The results revealed that the adsorption of AB25 onto zeolite-CTAB fitted better to Langmuir model and Zeolite fitted better with Freundlich model. The AB25 adsorption on zeolite-CTAB increases with an increasing temperature indicates that the preferential adsorption may occur at a higher temperature. The positive value of ∆H° in zeolite-CTAB material thermodynamic parameters indicates that the process was an endothermic process. These results indicate that zeolite-CTAB has high adsorbent efficiency and it is promising adsorbents for removing the dye AB25

Indonesian kaolin supported nZVI (IK-nZVI) used for the an efficient removal of Pb(II) from aqueous solutions: kinetics, thermodynamics and mechanism

A remarkably efficient Indonesian Kaolin (IK) supported nano zerovalent iron composite (IK-nZVI) has been synthesized, and subjected to the elimination Pb(II) from the wastewater. The results were authenticate the nZVI nanoparticles have a chain shape and establish as separable nanospheres with an average size (29.95 nm) on the surface of IK. The FTIR spectra demonstrate the presence of Al-O as well as Si-O bonds. XRD results demonstrate the presence of zerovalent iron. SEM confirmed less agglomeration of Fe(0) nanoparticles which improves the mechanical strength. The weak signals of Fe and O confirm the establishment of zerovalent iron in nanocomposite. TEM demonstrates that the nanocomposite has a chain like structure. Pb(II)percentage removal was improved by rise in the IK-nZVI amount which results in rising the adsorption site. The nanocomposite had on optimum Pb(II) sorption at pH range of 4.5–6.5. The amount adsorbent increasing with the Pb(II) removal percentage was decreased. Kinetics study demonstrated that Pb(II) sorption was accomplished through more than one processes. IK was proved active support to progress the dispersion, and steadiness of IK-nZVI nanocomposite. The sorption processes pollutant was estimated through the kinetics models, and different sorption isotherm equations like Langmuir (LM), Langmuir-Freundlich (L-F), and Freundlich (FL) isotherms. The IK-nZVI typically accompanies outstanding Pb(II) removal efficiency of 98% and 96.05% with a span of 5 and 10 min for low and high concentrations, respectively. Significantly, the results reveal the maximum adsorption capability of the IK-nZVI is 192.0 mg/g. The thermodynamic study shown endothermic and spontaneous adsorption onto the IK-nZVI surface. Specifically, the IK-nZVI nanocomposite possesses key advantages in terms of simple method, nature friendly, cost-effectiveness, and decent adsorption efficiency for the potential elimination of toxic metal ion (Pb(II)) in the aqueous phase