Modified Activated Carbon for Copper Ion Removal from Aqueous Solution

Because of increasing environmental awareness, it is becoming more important to remove harmful elements from water solutions. This study used activated carbon (AC) derived from waste wood-based panels as the base material, oxidized with nitric acid (OAC), and grafted with iminodiacetic acid (IDA-OAC) to improve the adsorption capacity and affinity for metals. The characterization of AC, OAC, and IDA-OAC was conducted via FTIR, SEM, N2 adsorption and desorption analysis, elemental analysis, Boehm titration, and point of zero charge (PZC). The instrument studies proved the modified increasing of the functional groups of the adsorbents. Moreover, batch and column experiments were conducted to evaluate the ability of the three adsorbents to remove copper ions from aqueous solution. In batch sorption, IDA-OAC had the highest adsorption capacity (84.51 mg/g) compared to OAC (54.74 mg/g) and AC (24.86 mg/g) at pH 5. The breakthrough point (Ct/Ci = 0.05) of copper ions for IDA-OAC occurred much later than AC in the column experiment (AC = 19 BV, IDA-OAC = 52 BV). The Langmuir isotherm and pseudo-second-model kinetics modeling could better fit with the data obtained from the batch sorption of AC, OAC, and IDA-OAC. The significant capacity and reusability of IDA-OAC displayed high applicability for water treatment.

Nitrogen Fertiliser Immobilisation and Uptake in the Rhizospheres of Wheat and Canola

Immobilisation of fertiliser nitrogen (N) by soil microorganisms can reduce N availability to crops, decreasing growth and yield. To date, few studies have focussed on the effect of different plant species on immobilisation of fertiliser N. Canola (Brassica napus) is known to influence the soil microbiome and increase mineral N in soil for future crops compared with cereals. We tested the hypothesis that canola can reduce immobilisation of fertiliser N by influencing the composition of the rhizosphere microbiome. To investigate this, we conducted a glasshouse soil column experiment comparing N fertiliser uptake between canola and wheat (Triticum aestivium) and partitioning of fertiliser N between plants and microorganisms. Plants were grown in soil to which high C:N ratio wheat residues and 15N-labelled urea fertiliser were applied. There was no difference between wheat and canola in fertiliser N uptake despite differences in fungal community composition and the carbon metabolising enzyme alpha-glucosidase in the rhizosphere. Canola obtained more soil-derived N than wheat. There was no significant difference in the rhizosphere bacterial communities present between wheat and canola and unplanted controls. Our results highlight the capacity of canola to increase mineralisation of soil N compared with wheat although the study could not describe the microbial community which facilitated this increase.

Methods to Improve nZVI Adsorbance on Silicates Surface for Nitrate Reduction

<p>Efforts to remove excess nitrate in the groundwater typically involves expensive ion-exchange membranes or slow reacting bio-reactors. Nano-sized zero valent iron (nZVI) has been used successfully to reduce nitrate into ammonia in various sites in USA and Europe. However, nZVI has a number of major setbacks associated with it, namely the tendency to agglomerate due to magnetic properties, and the possible toxicity due to the nano-sized material. To circumvent these two setbacks, nZVI could be adsorbed onto solid support. In this research, geothermal sediment microsilicate 600 (Misi) was utilised as a support. Initial results suggested that Misi has potential as a support for nZVI, however modifications were required to improve the adsorbance of nZVI onto Misi surface. Calcination, activation, acid wash and iron oxyhydroxide coating were used as surface modifications for Misi. It was found that the two most important modifications for nZVI adsorption was calcination at either 400 or 600 °C and acid washing in 5.6 M HCl. Equipped with this knowledge, other silica and silicates were also used to adsorb nZVI. For pure silica surfaces, 3-APTES and 3-TPTMS ligands and pore enlarging methods of calcination of porogen and salt wash were also used. nZVI was not able to be fully adsorbed on pure silica surfaces. Four other silicates were examined: Rice husk ash, Western Australia silica fume, Mt Piper fly ash, and precipitated aluminium silicate. Of these, only Western Australia silica fume and precipitated aluminium silicate showed potential as nZVI support. Based on the SEM-EDS XRD data of all the silica and silicates, it could be tentatively concluded that nZVI requires an aluminium silicate surface for successful adsorption. Aluminium silicate surfaces typically has an exchangeable cation present, and this cation might play a part in nZVI adsorption. The nZVI/Misi surface was then utilised to reduce nitrate. It was discovered that even though activation and FeOOH did not play a part in nZVI adsorption onto Misi surface, these two steps were important in reduction of nitrate, as the presence of activation and FeOOH increase the reduction of nitrate significantly within 60 minutes. The Misi-supported nZVI were also shown to be more stable in dispersion, and less agglomerated as shown in a sand column experiment.</p>

Methods to Improve nZVI Adsorbance on Silicates Surface for Nitrate Reduction

<p>Efforts to remove excess nitrate in the groundwater typically involves expensive ion-exchange membranes or slow reacting bio-reactors. Nano-sized zero valent iron (nZVI) has been used successfully to reduce nitrate into ammonia in various sites in USA and Europe. However, nZVI has a number of major setbacks associated with it, namely the tendency to agglomerate due to magnetic properties, and the possible toxicity due to the nano-sized material. To circumvent these two setbacks, nZVI could be adsorbed onto solid support. In this research, geothermal sediment microsilicate 600 (Misi) was utilised as a support. Initial results suggested that Misi has potential as a support for nZVI, however modifications were required to improve the adsorbance of nZVI onto Misi surface. Calcination, activation, acid wash and iron oxyhydroxide coating were used as surface modifications for Misi. It was found that the two most important modifications for nZVI adsorption was calcination at either 400 or 600 °C and acid washing in 5.6 M HCl. Equipped with this knowledge, other silica and silicates were also used to adsorb nZVI. For pure silica surfaces, 3-APTES and 3-TPTMS ligands and pore enlarging methods of calcination of porogen and salt wash were also used. nZVI was not able to be fully adsorbed on pure silica surfaces. Four other silicates were examined: Rice husk ash, Western Australia silica fume, Mt Piper fly ash, and precipitated aluminium silicate. Of these, only Western Australia silica fume and precipitated aluminium silicate showed potential as nZVI support. Based on the SEM-EDS XRD data of all the silica and silicates, it could be tentatively concluded that nZVI requires an aluminium silicate surface for successful adsorption. Aluminium silicate surfaces typically has an exchangeable cation present, and this cation might play a part in nZVI adsorption. The nZVI/Misi surface was then utilised to reduce nitrate. It was discovered that even though activation and FeOOH did not play a part in nZVI adsorption onto Misi surface, these two steps were important in reduction of nitrate, as the presence of activation and FeOOH increase the reduction of nitrate significantly within 60 minutes. The Misi-supported nZVI were also shown to be more stable in dispersion, and less agglomerated as shown in a sand column experiment.</p>

Heavy metals removal from landfill leachate by coagulation/flocculation process combined with continuous adsorption using eggshell waste materials

The use of agricultural waste materials to remove heavy metals from wastewater is attractive due to its simplicity and economic efficiency. In this study, the applicability of calcined eggshell waste materials (CES) for heavy metals removal from real wastewater were examined via transport column experiment preceded by coagulation/flocculation process.A column packed with granular activated carbon (GAC) is operated in parallel to CES column to evaluate the adsorptive attributes of CES. The findings are assessed from another set of column experiment consisting of sand followed by CES column to evaluate the effect of particulate matter on CES performance toward heavy metals removal. In coagulation experiment, alum addition at an optimum dose (3.0 g/L) reduced the total suspended solids (TSS) by 80%, whereas the Fe, Pb, Zn, Cu, Ni, and Cr were reduced by 80, 77, 76, 73, 56, and 49% respectively. Under the current applied hydrodynamic conditions, using sand column before CES column improved the removal efficiencies of Fe, Pb, Cu, Zn, Ni, and Cr from 50–92%, 55–93%, 60–87%, 53–76%, 45–65%, and 41–60% respectively. The whole results illustrate that CES can be competitive to GAC for heavy metals removal from landfill leachate, mainly if applied after PM removal by sand filtration.

DOPO-Modified Cellulose Microsphere: Preparation and Application for Selective Adsorption U(VI) under Acidic Solutions

Effective radioactive wastewater disposal is of great significance to the wide use of nuclear energy. In this work, 4, 4ˊ-[1, 4-phenyl-bis (9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-yl) dimethyneimino)] diphenol (t-DOPO) was used to modify microcrystalline cellulose microsphere (t-DOPOR) to further enhance it affinity toward U(VI) through radiation method. The t-DOPOR were characterized for structural, morphological, and thermal properties by FTIR, SEM and TGA, which prove that t-DOPO is successfully modified on cellulose. Combination the advantage of cellulose and t-DOPO, t-DOPOR possessed abundant functional group (-OH, -NH and P=O), and exhibited extremely strong affinity toward U(VI) with a maximum adsorption capacity of 51.51 mg/g at pH 3. Particularly, A large distribution, KdU, up to 2.54×104 mL g−1 is found, implying extremely strong affinity toward U(VI) than Ln(III) (La(III), Eu(III), Dy(III), Yb(III)) at the binary system. Dynamic column experiment confirmed that t-DOPOR could separate selectively U(VI) in column experiment. In addition, even in the simulated groundwater trace amount of U(VI) was also eliminated efficiently by t-DOPOR. Lastly, the adsorption mechanism elaborated by XPS analysis was inner-sphere surface complexation between U(VI) and -OH, -NH and P=O groups of t-DOPOR. Overall, the synthesized t-DOPOR may be utilized as a promising adsorbent for separation and remediation of U(VI) from wastewater.

Impact of temperature on the leaching of sulphate, Co, Fe, Mn, Ni and Zn from the Ballangen tailings deposit, Norway: a laboratory column experiment

Temperature is an important factor affecting the leaching of contaminants from waste deposits, especially in the Nordic region where temperature change is more drastic than other areas. In this study, the impact of temperature variation in the leaching of sulphate, Co, Fe, Mn, Ni and Zn from the Ballangen tailings deposit, northern Norway, was investigated using a column leaching experiment. Unoxidized tailings were fed into four columns, which were subsequently put into four wine fridges set at 5, 10, 14 and 18 °C, respectively. The columns were filled with 600 ml of deionized water from the top every second week. Leachate was collected at the bottom and tested for pH, conductivity and concentrations of , Co, Fe, Mn, Ni and Zn. The saturation index for ferrihydrite and the activity of Fe2+ in the leachate were calculated with PHREEQC. The results showed that the conductivity and leachate concentrations of , Co, Fe, Mn and Ni were highest at 14 and 18 °C, and lowest at 5 °C, which showed high tailings oxidation and subsequent leaching of contaminants at higher temperatures. X-ray photoelectron spectroscopic (XPS) analysis of the residual material confirmed the oxidation of sulphides and leaching of many elements. Ferrihydrite was supersaturated in the leachate from the 14 and 18 °C columns, which showed the oxidation of pyrrhotite and olivine and the precipitation of ferrihydrite. The cumulative mass of Zn leached out was highest at 10 °C, which might be the threshold temperature for the leaching of Zn.

Root and shoot growth of spring wheat (Triticum aestivum L.) are differently affected by increasing subsoil biopore density when grown under different subsoil moisture

A column experiment with five different pore densities (0, 1, 2, 3, and 4 pores column−1) and two varying moisture regimes (comparatively dry and comparatively moist regime) in the subsoil part of the columns was established. In each pore, Lumbricus terrestris was introduced for 28 days before sowing wheat plants. After 40 days of plant growth, watering was stopped to induce progressive topsoil drying. Parameters describing the shoot hydration, mineral uptake, and aboveground biomass were quantified. Root biomass and root length densities (RLD) were measured separately for six soil layers. Under dry subsoil conditions, plants grown under increasing biopore density showed an increase of the RLD and an improved shoot hydration but the aboveground biomass was unaffected. Since RLD but not root biomass was enhanced, it is assumed that roots were able to explore a larger volume of soil with the same amount of root biomass. Thereby, subsoil water likely was used more efficiently leading to an improved hydration. Under moist subsoil conditions, plants grown with increasing biopore density revealed enhanced shoot biomasses and nutrient uptake while the belowground biomass was unaffected. The improved nutrient uptake can be ascribed to, first, the higher subsoil water availability favoring mass flow driven nutrient uptake, and second, to direct and indirect effects of earthworms on the availability of soil nutrients. It is concluded that high biopore abundancies have the potential to improve not only the belowground but also the aboveground biomass. This, however, largely depends on subsoil moisture.

Reduction of Lead and Antimony Ions from the Crystal Glass Wastewaters Utilising Adsorption

The presented research examined five adsorbents, i.e., zeolite 4A, a mixture of three zeolites (4A, 13X, and ZSM-5), natural zeolite (tuff), activated carbon, and peat, and their potential capability for removal of exceeded ions of lead (Pb), antimony (Sb), sulphates (SO42−), and fluorides (F−) from real wastewater generated in the crystal glass industry, which was previously treated in-situ by flocculation, with the aim to attain the statutory values for discharge into watercourses or possible recycling. The screening experiment evidenced that the tuff was the most suitable adsorbent for the reduction of Pb (93.8%) and F− (98.1%). It also lowered wastewater’s pH sufficiently from 9.6 to 7.8, although it was less appropriate for the reduction of Sb (66.7%) as compared to activated carbon (96.7%) or peat (99.9%). By adjusting the pH of the initial wastewater to pH 5, its adsorption capacity even enlarged. Results from the tuff-filled column experiment revealed reduction of Pb up to 97%, Sb up to 80%, and F− up to 96%, depending on the velocity flow, and thus it could be used for post-treatment (and recycling) of wastewaters from the crystal glass industry. Moreover, the system showed an explicit buffering capacity, but negligible reduction of the SO42−.

Adsorption Behaviors and Mechanisms of Cu2+, Zn2+ and Pb2+ by Magnetically Modified Lignite

In order to solve the problems of high content of Cu2+, Zn2+ and Pb2+ in acid mine wastewater (AMD), and limited adsorption capacity of lignite, the lignite was used as raw material to prepare magnetically modified lignite (MML), and adsorption performance of lignite and MML on Cu2+, Zn2+ and Pb2+ was investigated by static beaker experiment and dynamic continuous column experiment. At the same time, the adsorption mechanism was revealed by means of scanning electron microscopy (SEM), X-ray diffractometer (XRD) and Fourier transform infrared spectrometer (FTIR). The results showed that the adsorption processes of lignite and MML on heavy metal ions were more consistent with the Langmuir model, obeying the quasi first-order model and quasi second-order model, respectively. In addition, the intraparticle diffusion model indicated that the adsorption processes were jointly controlled by multiple adsorption stages. The dynamic continuous column experiments showed that the average removal rates of Cu2+, Zn2+ and Pb2+ were 78.00%, 76.97% and 78.65% for lignite and 82.83%, 81.57% and 83.50% for MML, respectively. Compared with lignite, the adsorption effect of MML was better. From SEM, XRD and FTIR tests, it can be seen that the magnetic modification process successfully loads Fe3O4 onto the surface of lignite, making the surface morphology rougher, and the adsorption process of MML on Cu2+, Zn2+ and Pb2+ is related to the O-H stretching vibration of carboxylic acid ions and Fe-O stretching vibration of Fe3O4 particles.