Phosphorus Adsorption Capacity Research Articles

Modification of sludge-based biochar and its application to phosphorus adsorption from aqueous solution

Sludge-based biochar was first modified for the adsorption of phosphorus from aqueous solution. This study is to modify sludge-based biochar (SBC) via peroxidation with nitric acid and impregnation with ferrous ions to obtain a high adsorption capacity for phosphorus (P). The P adsorption capacity of the modified sludge biochar (M-SBC) was increased to 9.79 mg/g, a value almost 40 times higher than that of the original biochar. Among the adsorption parameters studied, pH was found to be particularly important to P adsorption. After modification, the point of zero charge of the M-SBC occurred at pH 6. The isotherms of P adsorption on M-SBC obeyed the Freundlich equation. An analysis of the adsorption thermodynamics indicated that the process of P adsorption on M-SBC was spontaneous and endothermic, increased the degree of disorder, and involved chemisorption. The main mechanisms of P adsorption were surface precipitation and electrostatic attraction.

Experiment on Recovery of Phosphorus from Aqueous Solution by Calcium Doped Fe3O4

Adsorption is an economical and effective method for recovering phosphate from wastewater. In order to improve the adsorption capacity of Fe3O4 for phosphate and for easy separation from water under the action of an external magnetic field, CaO2 was used in this study as an oxidant to partially oxidize Fe2+. A phosphorus recovery adsorbent, Ca doped Fe3O4 (CMIO), was prepared and was characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and vibrating sample magnetometer (VSM) techniques. The results showed that CMIO had a Ca2+ doped Fe3O4 crystal structure with a saturation magnetization of 38.82 emu·g-1, which was easily separated from water by using an external magnetic field. The phosphorus adsorption capacity of the CMIO decreased with an increase of pH value. When pH=2 and T=25℃, the maximum adsorption capacity was 24.10 mg·g-1, which is almost five times the adsorption capacity of pure Fe3O4. The phosphorus adsorption of CMIO was in accord with the Langmuir isotherm adsorption model, and the adsorption process followed the pseudo-second order kinetic model. The complexation of phosphate occurred on the inner surface of the CMIO to form a ≡Fe-Ca-P ternary complex, which can adsorb phosphorus. Compared with other anions in the aqueous solution, CMIO had good adsorption selectivity to PO43-, and the adsorbed PO43- could be desorbed by NaOH solution.The quality loss of the CMIO was less than 4% once, and multiple recycling was possible.

Application of Cold Region Regenerable Biomass in Phosphorus Adsorption in Reclaimed Water

In order to enhance the using efficiency of the adsorbent and decrease production costs, reclaimed saturation Lanthanum modified pine needles (LH pine needles) have been studied as a possible solution. Pine needles gathered from the woods of Northeast China area were used as raw material for generating LH pine needles by alkali-isopropanol treatment and chemical precipitation. To explore the utilization of LH pine needles as a recycling adsorbent in wastewater treatment plants (WWTPs) and laboratory water distribution. Results show that removal effective of phosphorus (P) by LH pine needles in low concentration reclaimed water of WWTPs was 41% and up to more than 92% in its adding standard. In the wide pH range, LH pine has an effective adsorption capacity for phosphorus; pH can also interfere with the adsorption capacity of LH pine as there is a negative correlation between them. The adsorption of phosphorus by LH pine needles is divided into three stages with a pH ranging from 3~11. Ligand exchange reaction, electrostatic reaction and Lewis acid reaction are PO43− adsorption mechanism. The analysis of the recycling efficiency of LH pine needles proved that LH pine needles have good regeneration performance. After being eluted by NaOH regeneration agent for more than 10 times, the adsorption efficiency of phosphorus can still be stable at over 90% in seven cycles.

Phosphorus and Nitrogen Adsorption Capacities of Biochars Derived from Feedstocks at Different Pyrolysis Temperatures

This study investigates the P and NO3− adsorption capacities of different biochars made from plant waste including rice straw (RSB), Phragmites communis (PCB), sawdust (SDB), and egg shell (ESB) exposed to a range of pyrolysis temperatures (300, 500 and 700 °C). Results indicate that the effect of pyrolysis temperature on the physiochemical properties of biochar varied with feedstock material. Biochars derived from plant waste had limited adsorption or even released P and NO3−, but adsorption of P capacity could be improved by adjusting pyrolysis temperature. The maximum adsorption of P on RSB700, PCB300, and SDB300, produced at pyrolysis temperature of 700, 300 and 300 °C, was 5.41, 7.75 and 3.86 mg g−1, respectively. ESB can absorb both P and NO3−, and its adsorption capacity increased with an increase in pyrolysis temperature. The maximum NO3− and P adsorption for ESB700 was 1.43 and 6.08 mg g−1, respectively. The less negative charge and higher surface area of ESB enabled higher NO3− and P adsorption capacity. The P adsorption process on RSB, PCB, SDB and ESB, and the NO3− adsorption process on ESB were endothermic reactions. However, the NO3− adsorption process on RSB, PCB and SDB was exothermic. The study demonstrates that the use of egg shell biochar may be an effective way to remove, through adsorption, P and NO3− from wastewater.

Utilization of coal fly and bottom ash pellet for phosphorus adsorption: Sustainable management and evaluation

Recycling of coal combustion solids can have several environmental benefits. The objective of this study was to evaluate a sustainable approach to recycle coal fly ash and bottom ash as pelletized-adsorbents for dissolved phosphorus (P). Sodium Dodecyl Sulfate (SDS), a foaming agent, was added to enhance the phosphorus adsorption capacity of fly ash pellets (FAP) and bottom ash pellets (BAP) during the pellet fabrication. Ten types of fly ash pellets and bottom ash pellets with varying Sodium Dodecyl Sulfate proportions (FAP-0/BAP-0: 0% SDS; FAP-1/BAP-1: 2% SDS; FAP-2/BAP-2: 4% SDS; FAP-3/BAP-3: 6% SDS; FAP-4/BAP-4: 8% SDS by weight) were manufactured with a high temperature (700℃) modification process. The results indicated that the bottom ash pellet was more suitable adsorbent than fly ash pellet due to the better phosphorus adsorption capacity and lower heavy metal leaching. After the addition of Sodium Dodecyl Sulfate, the volumetric porosity of fly ash pellets and bottom ash pellets increased by 45.5%–163.6%, 52.9%–76.5%, respectively. However, higher Sodium Dodecyl Sulfate fraction did not result in better pellet phosphorus removal, since FAP-2 and BAP-3 resulted in the highest phosphorus removal among the pellets tested in this study. The results from X-ray diffraction demonstrated that Calcium and Silica were the major phases in the pellets. This study provides a feasible approach to reuse fly ash and bottom ash as effective pelletized-adsorbents for water quality improvement. These pellets can be applied in edge-of-field and in-stream treatment to control P loss from the agricultural area.

Assessment of nutrient removal and microbial population dynamics in a non-aerated vertical baffled flow constructed wetland for contaminated water treatment with composite biochar addition

A novel composite biochar (NCB) was produced from the pyrolysis of co-fermentation products of sewage sludge, food wastes and rice straw, and exhibited higher nitrogen and phosphorus adsorption capacity due to the larger surface area (14.7 m2 g−1) and higher Ca content (51753.7 mg kg−1) than single rice straw biochar. The addition of NCB was then investigated in a non-aerated vertical baffled flow constructed wetland (VBFCW) for contaminated water treatment. The VBFCW with NCB addition significantly improved CODMn, NH4+-N, TN and TP removal efficiencies of 83.3 ± 5.3%, 95.9 ± 3.4%, 28.0 ± 4.0% and 59.5 ± 11.8%, respectively, at a hydraulic retention time (HRT) of 3 d. In addition, the TN and TP removal rates at a decreased HRT of 2 d were much higher than those at an HRT of 3 d without NCB addition. The presence of NCB in the VBFCW system enhanced nutrient adsorption and improved the enrichment of bacteria for organic and nitrogen removal mainly including the genera Bacillus and Lactococcus.

Analysis of Transport and Transformation Characteristics Between Dissolved Phosphorus and Particulate Phosphorus in Water of the Three Gorges Reservoir

To understand the difference between transport coefficients of water runoff, sand discharge, and phosphorus flux in each subsection of a river, a judgement method for analyzing the characteristics of phosphorus transport and transformation in water of rivers was established in this study. Based on the measured data of water runoff, sand discharge, and phosphorus fraction concentrations in the water of the Three Gorges Reservoir (TGR) in January and July 2015, characteristics of phosphorus transport and transformation in the water were analyzed by using the conceptual method. The results showed that the predominant phosphorus fraction in water of the TGR was total dissolved phosphorus (TDP), which accounted for 51%-96% of total phosphorus in water. The TDP flux relative to runoff in the TGR decreased in January 2015 That was caused by the adsorption of TDP by suspended particles in the dry season. In contrast, TDP flux showed additive effect relative to water runoff in July 2015 due to exogenous water inputs with high TDP concentrations in the wet season. Both sand and total particulate phosphorus (TPP) presence in the water showed obvious sediment and retention characteristics during the two periods. The TPP flux presented an additive effect relative to sand discharge, meaning that the major transformation direction of phosphorus fractions was from TDP to TPP. The subsection between Qingxichang and Wanzhou was the main retention area of water, sand, and phosphorus in the TGR, which can be associated with the enhancement of phosphorus adsorption capacity caused by particle size reduction of suspended particles in the subsection.

Phosphorus removal mechanisms from domestic wastewater by membrane capacitive deionization and system optimization for enhanced phosphate removal

Membrane capacitive deionization (MCDI) is an emerging technology for effective removal of charged pollutants from the water sources including domestic wastewater. In this work, a lab-scale MCDI system was employed to investigate its feasibility for effective phosphorus removal from domestic wastewater. The effect of phosphate equilibrium reactions on the ion sorption behaviour was studied in sodium phosphate buffer solution at typical pH range maintained in a real domestic raw wastewater effluent (between 6.5 and 8.5). The results demonstrated that phosphate equilibrium system has positive impact on the degree of inorganic phosphorus (P) adsorption capacity in aqueous solution. In addition, the ion selectivity of P over other co-existing anions (Cl-, SO42-) were experimentally studied using a synthetic wastewater solution. And it was found that the preferential electrosorption sequence of the competitive anions is: Cl-> SO42- > P, while the initial ion concentration order in the synthetic feed solution is: Cl- 1.90 mM> P (0.40 mM)> SO42- (0.32 mM). The experiments with diverse operating conditions revealed that the optimal adsorption of inorganic phosphorus over chloride and sulphate can be achieved in some extent with slower flow rates and higher applied potentials (less than 1.23 V).

Efecto del uso del suelo en las formas y disponibilidad de fósforo de un Andisol de la Meseta P’urhépecha, Michoacán.

Andisols are distinguished by a high phosphorus (P) adsorption capacity, which is a restrictive factor for plant growth. This study, it was hypothesized that the availability of P in the different forms extracted sequentially, would vary according to the land use, and its exchange would depend on its chemical characteristics. For this purpose, sequential extraction and isotopic dilution techniques were utilized to measure the effect of land use systems and corresponding P fertilizer inputs on size of inorganic and organic P forms and their lability. An Andisol sample from a field site with a long history of P amendments and another sample from a contiguous forested area under natural vegetation were treated with applied KH232PO4. The soil samples were sequentially extracted for P fractions after 49 days (d) of incubation. Recovery of 32P in each P form was evaluated. The recovery of 32P in all soil P fractions exhibited that 32P had undergone exchange with the native P. The exchange reaction occurred mainly in the Pi fractions. Resin-Pi, Bic-Pi and NaOH-Pi were increased by P fertilization, with the greater level occurring for NaOH-Pi. The highest increase of the 32P recovered in the NaOH0.1-Pi fraction of the P-fertilized Andisol shows that the added P changed into this form stays highly exchangeable and contributes P fertility to this soil type. The recalcitrant inorganic fractions contained almost no exchangeable P. In contrast, in native soil with no P input, more than 20% of the 32P was recovered in Bic-Po and NaOH-Po forms 49 d after the labeled P was added. The change in soil P fraction was associated with soil type and P addition. Nonetheless, the applied P persisting in the fraction can be exchangeable with solution P and, hence, can be plant-available.

Study on spatial-temporal distribution of different forms of phosphorus in wetland sediments

As an important factor for controlling phosphorus adsorption and release in wetland system, the forms of phosphorus in sediment has a decisive effect on phosphorus retention and release. Four different wetland systems were selected to study the phosphorus status and its environmental effects in wetland sediment. Phosphorus forms in sediments were related to aquatic plant characteristics. In the Vallisneria Linn. wetland system, the content of Ca-P of sediment was higher than the other systems because of its higher pH of the water. The maximum phosphorus adsorption capacity is 766.82-840.27 mg/kg. The content of Ca-P and TP have very good correlation with Smax. When the phosphorus concentration in the water is lower than 0.1mg/L, the surface sediment is no longer a “sink” of phosphorus but a “source” of phosphorus. The changes of TP in four wetland sediments basically follow a similar trend. The phosphorus content in the sediment decreased during the growth period of aquatic plants, and the wetland sediment as the phosphorus “source” provided the biomass for the growth of the aquatic plants. In autumn and winter, phosphorus in plants is released into wetland again with the decay of plants, resulting in the increase of phosphorus content in sediment.

Adsorption of phosphorus by using magnetic Mg-Al-, Zn-Al- and Mg-Fe-layered double hydroxides: comparison studies and adsorption mechanism.

Mg-Al, Zn-Al and Mg-Fe magnetic layered double hydroxide (LDH) adsorbents were synthesized. The adsorption effect and influencing factors of these adsorbents were explored, and the adsorption mechanism of phosphorus was studied with advanced instruments. The results showed that the best adsorption performance was observed when the molar ratio of metals was 3 for the magnetic LDH adsorbents, and the maximum adsorption amount for phosphorus was 74.8, 80.8 and 67.8mg/g for Mg-Al, Zn-Al and Mg-Fe LDHs, respectively. Pseudo-second-order kinetics could be used to describe the adsorption process of phosphorus onto the magnetic LDHs. The adsorption of phosphorus onto the magnetic LDHs was an exothermic process. Lower temperatures were favourable for adsorption, and the adsorption of phosphorus onto the magnetic LDHs was a spontaneous process. When the solid-liquid ratios were 0.10g/L, 0.10g/L and 0.05g/L for Mg-Al, Zn-Al and Mg-Fe magnetic LDHs, respectively, the highest adsorption amount of phosphorus was achieved for each magnetic LDH. The maximum adsorption amount was observed at pH values of 6.0-8.0. The inhibitory effect of HCO3- on the adsorption capacity of phosphorus onto the magnetic LDHs was the strongest at a higher HCO3- concentration level. The relative content of -OH significantly reduced after adsorption of phosphorus by the FTIR analysis, which indicated that the mechanism of phosphorus removal was mainly through the exchange between hydroxyl on the adsorbent surface and phosphorus in water. XPS studies showed that oxygen provided electrons during the adsorption of phosphorus.

Samples disturbance overestimates phosphorus adsorption capacity in soils under long-term application of pig slurry

ABSTRACTGrinding soil for analysis causes the destruction of aggregates and may expose adsorption sites that would not be available for adsorption in the soil with preserved structure. The study aimed to evaluate the adsorption of P in three soils with and without preserved structure, submitted to pig slurry (PS) application for a long time. Three soils (Acrisol, Ferralssol and Nitisol) with contrasting textures and P contents, with and without PS were selected and samples were collected with and without preserved structure in the 0–10 and 10–20 cm layers. The undisturbed soil columns were submitted to continuous flow, for 10–24 h, of 300 mg L−1 P solution and, at regular intervals, aliquots of the resulting solution were collected and the P content was determined. These data were adjusted exponential models to estimate the maximum adsorption of P. The maximum capacity of P adsorption of the soils were 1.4 to 14 times higher in the milled soil samples, making it clear that the destruction of the soil structure, and consequently the porosity and the preferential paths of percolation of the liquids in the soil leads to an overestimation of the soil capacity to adsorb the P applied to the surface.

Phosphate dsorption from aqueous solution by mesoporous adsorbent Fe-SBA-15

The excessive amount of phosphorus (P) in water could lead to environment pollution such as eutrophication. Thus, an effective and economical way of removing phosphorus must to be developed. In this study, Fe-SBA-15 was synthesized to investigate the adsorption capacity of phosphorus. The structure and morphology of Fe-SBA-15 were tested by scanning electronic microscopy and transmission electron microscope. According to the experiments, the 30%Fe-SBA-15 exhibited the best phosphorus removal efficiency among different percentages of Fe. The influence of time, adsorbent dose, initial phosphorus concentration, pH and comparative ion were tested in this study. The adsorption rate of phosphorus increases with the increase of adsorption dose. The influence of comparative ion followed the order SO42-> NO3->Cl-. The optimistic pH for adsorption was 3.2. The adsorption of phosphorus onto Fe-SBA-15 reached equilibrium in about 80 minutes. The results demonstrated that Fe-SBA-15 is a potential candidate for removing phosphorus from contaminated water.

Nitrogen and Phosphorous Adsorption Characteristics of Suspended Solids Input into a Drinking Water Reservoir via Typhoon Heavy Rainfall

During typhoon "Mujigae" in October 2015, water samples and surface sediments were collected from Gaozhou Reservoir, a drinking water reservoir, for simulation and analysis of the kinetics of suspended solids adsorption to nitrogen and phosphorus and the adsorption isotherms of suspended solids with different particle sizes and different concentrations. The results showed no obvious nitrogen adsorption of suspended solids of Gaozhou Reservoir. However, the adsorption effect to phosphorus by suspended solids was significant and the equilibrium time of phosphorus adsorption was 10 hours. The adsorption capacity of phosphorus increased with the decrease of sediment particle size when particle sizes were less than 0.25 mm, whereas it increased with the increase of suspended solids concentration when the concentration was in the range of 0.2-2.0 kg·m-3. The adsorption isotherm of suspended solids to phosphorus conformed to the Langmuir and Freundlich models, and the maximum adsorption capacity increased with the decrease of suspended solids particle sizes, which increased with the increase of suspended solids concentrations. The maximum adsorption capacity of suspended solids to phosphorus was 0.073-1.776 mg·g-1. These results indicated that the increase of suspended solids concentration due to the heavy rainfall of the typhoon promoted the adsorption of suspended solids to phosphorus, which reduced eutrophication in Gaozhou Reservoir.

A hierarchical porous adsorbent of nano-α-Fe2O3/Fe3O4 on bamboo biochar (HPA-Fe/C-B) for the removal of phosphate from water

A novel and magnetic hierarchical porous adsorbent functionalized by coating α-Fe2O3/Fe3O4 on bamboo biochar (HPA-Fe/C-B) is prepared and tested for the removal of phosphorus from aqueous solutions. The effect of phosphorus (P) concentration, temperature, pH, adsorbent grain size, adsorbent dosage, and contact time on phosphorus adsorption is investigated. Results show that by increasing the initial concentration from 2 to 10 mg-P/L, the phosphorus adsorption capacity of HPA-Fe/C-B (dg 0.11 mm and contact time 12 h) increases from 0.20 to 2.46, 2.64, and 2.81 mg-P/g and the phosphorus removal is reduced from 99.2 to 49.2 wt%, 99.4–52.8 wt% and 98.8–55.4 wt%, at temperature of 25, 35, and 45 °C, respectively. The phosphorus adsorption capacity of the unpulverized HPA-Fe/C-B (dg 1.59 mm) is from 0.18 to 0.66 mg-P/g in the concentration range of 2–10 mg-P/L, respectively, which is in the same order of magnitude as that of pulverized HPA-Fe/C-B or nano-size iron adsorbents reported in the literature. Kinetic and equilibrium adsorption results fitted well by the intra-particle diffusion and the Langmuir adsorption isotherm, respectively.

Effect of Preparation Methods on Phosphate Adsorption by Iron-Titanium Binary Oxide: Coprecipitation and Physical Mixing

To investigate the effect of preparation methods on surface characteristics and adsorption properties of the formed metal composite oxides, two kinds of iron-titanium binary oxides were synthesized by a coprecipitation method or a physical mixing method and were denoted as CFe-Ti and MFe-Ti, respectively. The prepared CFe-Ti and MFe-Ti were systematically characterized using SEM, XRD, BET, and FTIR techniques. Their phosphate adsorption behaviors were also studied via batch adsorption experiments. Compared with pure FeOOH and TiO2, CFe-Ti exhibited a looser nanostructure with more pore and surface hydroxyls. Moreover, the CFe-Ti had a high maximal phosphorus adsorption capacity of 40.6 mg·g-1, which is about 1.5 times and 2.4 times as high as that of pure FeOOH (27.2 mg·g-1) and TiO2 (16.7 mg·g-1), respectively. This suggests that an obvious synergistic effect is present in the CFe-Ti system. However, the morphology and structure of MFe-Ti were not significantly different from those of pure FeOOH and TiO2. The maximal adsorption capacity of MFe-Ti was 22.7 mg·g-1, which is obviously lower than that of CFe-Ti and even lower than that of pure FeOOH. Evidently, there is no synergistic effect in the MFe-Ti system. In addition, phosphate adsorption mechanisms at the surface of CFe-Ti and MFe-Ti were the same as those of their component oxides, and chemical adsorption occurred at the surface of the oxides through the formation of inner-sphere complexes. Therefore, the surface characteristics and adsorption properties of the metal composite oxides were closely related to their preparation methods. The coprecipitation method was a simpler and more economical way than the physical mixing method to fabricate a highly effective iron-titanium binary oxide for phosphate adsorption.

Mineralogy and Maximum Phosphorus Adsorption Capacity in Soybean Development

The low natural fertility of tropical soils and the mineralogy almost dominated by iron and aluminum oxides limit the availability of phosphorus (P) to the plants, causing negative impacts on soybean yield. Objective was to evaluate the effect of phosphate fertilization on soils with different maximum phosphorus adsorption capacities (PAC) in soybean development. The experiment was carried out under greenhouse conditions, using Red-yellow Latosol (RYL) and a Typic Hapludalf (TH) soil as substrate. The analyses were performed by a completely randomized experimental design in a 5 × 2 factorial arrangement with three replications. The treatments consisted of 5 doses of P applied, corresponding to 0, 1, 6, 12, and 24% of PAC of each soil. In the soil, the mineralogy of the clay fraction (hematite, goethite, gibbsite and kaolinite) and crystallographic attributes were characterized. In the plant, we evaluated growth and pod production. The PAC of the soils ranged from 220 to 650 mg dm-3 with higher value in the RYL associated to clayey oxidic mineralogy and texture in relation to the TH of kaolinite origin and sandy texture, where the higher energy of adsorption observed was to TH. Phosphorus application from 16 to 21% of PAC, independently of the soil, promotes the same pattern of response with improvements in soybean development evidenced by increases in P content in plant tissue, plant height, root volume and aerial dry mass.

Influencing Factors for Phosphorus Removal by Modified Bio-ceramic Substrates Coated with ZnAl-LDHs Synthesized by Different Modification Conditions

Under different pH conditions, the hydrothermal and co-precipitation method was used to synthesize layered double hydroxides (LDHs) coated on bio-ceramic substrates with three different Zn2+/Al3+ molar ratios. Applying the original and six kinds of modified bio-ceramic substrates coated with ZnAl-LDHs (bio-ceramic/ZnAl-LDHs) in simulated vertical-flow constructed wetlands, experiments for phosphorus removal and isothermal adsorption were conducted to analyze the mechanism and effect of each synthesis factor. The results showed that ZnAl-LDHs (pH=11) had a more obvious effect on phosphorus removal, especially for bio-ceramic/ZnAl-LDHs (pH=11, 1:1), whose average removal rates of TP, TDP and SRP were enhanced over 70%. Its maximum adsorption capacity for phosphorus was three times higher than that of the original bio-ceramic. Both pH and Zn2+/Al3+ molar ratio affected the configuration and coating properties of bio-ceramic/ZnAl-LDHs at the time of synthesis, and pH was the main synthesis factor for phosphorus removal efficiency of bio-ceramic/ZnAl-LDHs. Through reasonable regulation of pH and Zn2+/Al3+ molar ratio when bio-ceramic/ZnAl-LDHs was synthesized, the phosphorus removal efficiency could be improved effectively.

Characterizing the correlation between dephosphorization and solution pH in a calcined water treatment plant sludge.

This study focused on characterizing the correlation between the dephosphorization process of calcined water treatment plant sludge (C-WTPS) and the solution initial pH in batch experiments. The specific aim was to illustrate the effect of different initial pH on the adsorption and desorption of phosphorous in C-WTPS. In addition, the effects of solution initial pH on the release of ammonia nitrogen and total organic carbon (TOC) from C-WTPS and the change of pH after adsorption were also investigated. The results demonstrated that the initial pH significantly influenced the adsorption of phosphorus on C-WTPS. When initial pH was increased from 3 to 10, the phosphorous absorption capacity reduced by 76.5%. Especially, when the initial pH reached to 11, the phosphorus adsorption capacity became a negative value, indicating that C-WTPS released phosphorus into the solution. The addition of C-WTPS to the solution had little impact on the initial pH of the solution. The absorbed phosphorous on C-WTPS was relatively stable in the pH range of 3 to 10. Nevertheless, when the solution pH was higher than 11, it can be easily released into the solution. Furthermore, by comparison with WTPS, C-WTPS released less ammonia nitrogen and TOC into the solution and adsorbed more phosphorus from the solution in the experimental pH range. Therefore, C-WTPS is more suitable to serve as a cost-effective sorbent for phosphorus removal.

Efficiency of waste clinker ash and iron oxide tailings for phosphorus removal from tertiary wastewater: Batch studies

Abstract Phosphorus removal from wastewater using waste materials as novel adsorbents has been gaining attention. This work exploits and compares phosphorus adsorption capacities of iron oxide tailings and clinker ash waste from the copper–nickel mine (BCL LTD) in Botswana. The surface heterogeneity of the media was investigated using scanning electron microscope, which revealed a highly porous structure of clinker ash as compared to iron oxide tailings. The chemical and mineralogical composition was determined using the X-ray Fluorescence and X-ray Diffractometer respectively. The adsorption kinetics, equilibrium isotherms and regeneration potential of the media were investigated through batch experiments at room temperature using real wastewater. XRF results revealed 25.1% of iron oxide in tailings and 5.3% for clinker ash. The concentrations of aluminium oxide were 5.4% and 11.7% for tailings and clinker ash respectively. Small amounts of phosphorus were present in both media before the experiment and there was an increase of phosphorus in used tailings whereas in clinker ash there was a reduction of phosphorus suggesting retention of phosphorus by tailings and desorption by clinker ash. Pseudo second order model best described the kinetics of adsorption onto both media with R2 values of 0.99 for both media compared to pseudo first values of 0.98 and 0.96 for tailings and clinker ash respectively, suggesting that chemisorption was the dominant force. Intra-particle diffusion model revealed that intra-particle diffusion was not the solely rate controlling mechanism but other mechanisms such as mass transfer were involved as well. The equilibrium data for both iron oxide tailings and clinker ash were best described by Langmuir model, which suggested a monolayer adsorption process with homogeneous distribution of energies. The batch results (Langmuir) indicate that iron oxide tailings have a higher phosphorus removal capacity (1.29 mg P g−1 media) than clinker ash (0.29 mg P g−1 media). The iron oxide tailings demonstrated high regeneration potential with 87%, 81% and 56% phosphorus removed during first, second and third cycle compared to 24%, 5% and 0.6% shown by clinker ash. This study demonstrated that these two mine wastes have capabilities to remove phosphorus, with iron oxide tailings having more potential than clinker ash. Iron oxide tailings is a better phosphorus adsorbent, thus it could be utilised in improving the quality of wastewaters as well as providing a waste disposal option for the mine.