Removal Of Phosphate In Wastewater Research Articles

Preparation of an activated adsorbent from water treatment plant sludge for phosphate removal from wastewater: optimization, characterization, isotherm, and kinetics studies

Abstract Purifying water for diverse uses is vital, but concerns lie with the sustainability and accessibility of purification materials. As such, this study converted readily available water treatment plant sludge (WTPS) into activated adsorbent for phosphate removal in wastewater. WTPS was activated via thermal activation at 300 °C temperature and chemical activation processes of 3 M acid concentration, 4 h activation time, and 75 °C activation temperature, and then characterized using Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared, elemental analyzer, and differential scanning calorimetry. SEM and BET analyses revealed a highly porous adsorbent (279.2 m2/g) for efficient adsorption. On top of the activation process, preliminary experiments and numerical optimization using response surface methodology (RSM) were designed and conducted. Through optimizing conditions, it was found that 70 min of contact time, pH 3, 3 g/L adsorbent dose, and 30 mg/L initial phosphate concentration as optimal, yielding 83% removal efficiency. Furthermore, adsorption kinetics and isotherm models were examined and the second-order kinetics and Langmuir isotherm models indicated best fit. Notably, the activated sludge could be regenerated for three cycles before efficiency dropped below 70%. Thus, activated WTPS presents a promising, sustainable, and readily available adsorbent for phosphate removal in wastewater treatment.

Achieved advanced wastewater phosphate removal via improved ionic interference resistance in a migration-electric-field assisted electrocoagulation (MEAEC) system with modified-biochar pseudocapacitor electrode

The capacitive deionization-assisted electrocoagulation system has promising application potential in advanced phosphate removal of its low electricity consumption and sacrificial anode material. Phosphate removal in wastewater is crucial since excess phosphate might lead to eutrophication. However, the complex ion composition in raw wastewater can influence the effective phosphate removal by competing with the precipitable metal ions during electrocoagulation. In this study, a novel migration electric-field assisted electrocoagulation (MEAEC) with an assisted capacitive electrode made of N-doped and Fe-La co-modified biochar (LFNB) to achieve specific phosphate electro-adsorption for effective advanced phosphate removal. The LFNB-MEAEC achieved ultrahigh phosphate removal with the effluent of 0.1 mg/L in synthetic and raw municipal wastewater and met the first Grade A standard of total phosphate in the discharge standard of pollutants for municipal wastewater treatment plant (DSPMWTP) in China. The commonly observed coexisting ions in wastewater and a pH range of 2–12 did not significantly fluctuate the phosphate removal of LFNB-MEAEC. Cyclic voltammetry and charging-discharging tests confirmed the high phosphate affinity and excellent durability of LFNB in ion-interference circumstances. The MEAEC assisted with selective-adsorption capacitive electrodes and provided an effective and practical method for advanced phosphate removal from low-phosphorus-contaminated wastewater. The MEAEC with a selective-adsorbed capacitive electrode improved phosphate removal by 21 % (from 74 ± 1.7% to 95 ± 1.0%), reduced the energy consumption by 65.7% (0.012 kWh m−3-wastewater), and saved the sacrificial anode material by 67.5% (from 200 to 65 g m−3-wastewater) than those of MEAEC without phosphate-selective electrode in the same period (Sacrificial anode working time 200 s).

The adsorption behavior and mechanism for arsenate by lanthanum-loaded biochar with different modification methods

Lanthanum (La)-loaded biochar (BC) was considered as an efficient adsorbent for phosphate removal in wastewater. Arsenate has a similar chemical structure to phosphate, however, performance and mechanisms of arsenate adsorption onto La-doped biochar are less studied and remain unclear. In this study, La-modified biochar (BC) was prepared using two dinstinct methods: pyrolysis of LaNO3-doped rice husk (pre-pyrolysis modification, referred to as La-BC) and pyrolysis of LaNO3-doped rice husk biochar (post-pyrolysis modification, referred to as BC-La). Isotherm experiments showed that the maximum arsenate adsorption content onto La-BC and BC-La was similar, respectively of 21.3 mg g−1 and 16.5 mg g−1 at pH = 5. Combined results of SEM-EDS, FTIR, and XPS analyzing revealed that La oxides and hydroxides loaded on BC played a vital role in arsenate adsorption. Electrostatic attraction and ligand exchange were considered as key mechanisms for arsenate adsorption. Compared to La-BC, the results revealed that La oxides/hydroxides exhibited more crystalline structures on BC-La. Moreover, the BC-La displayed more efficient adsorption capabilities over a wider pH range (pH 4–10) than La-BC. The XPS O1s spectra analysis confirmed the formation of different inner-sphere complexes on La-BC and BC-La. Results of this study revealed mechanisms of arsenate adsorption onto La-modified biochar, and highlighted that the adsorption behavior of arsenate onto La-modified biochar could be significantly influenced by modification methods.

Enhanced removal of phosphate by electrogenerated iron combined with mechanically activated calcite

Fe electrocoagulation is efficient for the removal of phosphate with low energy consumption, whereas suffers from the high concentrations of the total dissolved Fe (TDFe) in the effluent. In this study, mechanically activated calcite was used to combine with the electrogenerated Fe to improve the removal efficiency of phosphate and reduce the concentrations of TDFe. The removal efficiency of phosphate (initial concentration 1.0 mg/L) in 30 min was significantly increased (88 %) by mechanically activated calcite combined with electrogenerated Fe method, compared with mechanically activated calcite method (43 %) and electrogenerated Fe method (53 %) separately. The concentration of TDFe in the effluent reduced from 4.9 mg/L with electrogenerated Fe method to 0.2 ∼ 0.5 mg/L with mechanically activated calcite combined with the electrogenerated Fe method. The mechanically activated calcite combined with electrogenerated Fe method was confirmed by the efficient removal of phosphate in the biological treatment effluent from a municipal wastewater treatment plant reached a removal efficiency of approximately 100 % (reduced from 1.33 mg/L to 0.006 mg/L) and in the rainfall runoff from a fertilizer enterprise reached a removal efficiency of 98 % (reduced from 3.86 mg/L to 0.075 mg/L). The removal mechanism was proposed. The Fe-P polymer was formed in the dissolved phase. The mechanical activation improved the solubility of calcite and provided dissolved Ca2+, as well as increased the surface area of calcite and provided more adsorption sites. Therefore, the mechanical activation promoted the adsorption of the Fe-P polymer onto the surface of the mechanically activated calcite. This study provided an efficient method for the removal of phosphate in wastewater and simultaneously reducing the concentrations of TDFe in the effluent.

Low temperature synthesis of nitrogen-rich biomass for high-performance removal of phosphate

Eutrophication in water bodies provokes the exploit of efficient tactics for phosphate removal from wastewaters. Herein, biowaste oil-tea shell (OTS) was adopted as a precursor. Through a facile two-step dipping method of nitric acid (HNO3) and polyethyleneimine (PEI), the functionalized OTS (denoted as NP-OTS) was prepared and applied for the efficient removal of phosphate in wastewater. Characterization using XRD, FTIR, SEM and XPS showed that the as-obtained NP-OTS were mainly cellulose with abundant N-containing groups. The effect of solution pH, adsorption dosage, contact time, initial concentration, and co-existing ions were systemically investigated. As a result, the adsorption behavior of phosphate on NP-OTS was in best pertinence with pseudo-second-order kinetic model and Langmuir model, and the thermodynamics results suggested that the adsorption of the phosphate is spontaneous. The maximum uptake capacity of NP-OTS was 125.24 mg/g estimated by Langmuir model, which was about 4.4-fold higher than the pristine oil-tea shell (28.32 mg/g), and over 1.4-fold higher than either the HNO3 modified OTS (65.19 mg/g) or the PEI decorated OTS (83.94 mg/g) at 25 °C. The phosphate adsorbed NP-OTS was also easy to regenerate within five stable cycles. Furthermore, electrostatic adsorption and hydrogen bonding were revealed as the underlying adsorption mechanism. This work paves a new way for the high-value utilization of biowaste and the removal of phosphate in acid wastewater.

Precipitation of Orthophosphate in a Wastewater Treatment Plant

Different individually applied commercial salts at different concentrations are generally used to precipitate contaminants in wastewater. In this study, we developed a treatment complementary to the lagoon system of a wastewater treatment plant by adding a combination of trivalent metal salts to chemically precipitate phosphate contaminants. Laboratory tests were conducted to determine the most efficient treatment for the removal of phosphate in wastewater by analyzing orthophosphate using the ascorbic acid method. Three trivalent metal salts—iron (III) sulfate, aluminum (III) sulfate, and iron (III) chloride—were combined with each other at three different concentrations, obtaining an experimental design involving 27 treatments replicated three times each. Analysis of variance (ANOVA) with Tukey’s test revealed the treatment for which the highest percentage of orthophosphate removal (99.04%) was obtained. Finally, the selected treatment was implemented for field evaluation over three weeks, obtaining an average removal of 93.13%.

Strong Immobilization of Phosphate in Wastewater onto the Surface of MgO-Modified Industrial Hemp-Stem-Driven Biochar by Flowerlike Crystallization

Removal of phosphate in wastewater is significant and available to control eutrophication and adsorption is one of the most promising treatment methods. In this work, MgO-modified industrial hemp s...

Phosphate Removal in Wastewater by Adsorption on Calcium Carbonate and Calcium Oxide from Eggshell

Phosphate Removal in Wastewater by Adsorption on Calcium Carbonate and Calcium Oxide from Eggshell

Phosphorus removal from wastewater by ionic exchange using a surface-modified Al alloy filter

In this study, a cost-effective and eco-friendly route for removal of phosphate in wastewater was demonstrated using an Al alloy foam filter with a mesoporous aluminum hydroxide (Al(OH3) film. The mesoporous Al(OH)3 film on which the ion exchange and adsorption of phosphate occur was generated using a simple alkali surface modification process. For higher phosphate removal by the surface-modified Al alloy foam filter, the number of filters was increased up to 20, which achieved 90% phosphate removal within a very short contact time. As a recycling process, a second alkali surface modification was applied to the used filter after phosphate adsorption. It clearly indicated that the used filter can be recycled via a second alkali surface modification due to the ion exchange mechanism. It was shown that an alkali surface-modified Al alloy foam filter is a powerful candidate for phosphate removal in water treatment facilities.

Nitrogen and phosphate mass balance in a sub-surface flow constructed wetland for treating municipal wastewater

This paper reports on the feasibility of using sub-surface horizontal flow constructed wetlands to treat municipal wastewater in Hong Kong. Two different hydraulic retention times (10-day and 5-day) and different types of treatments (with and without vegetation) were investigated. Better performance in the planted treatments was obtained in both hydraulic retention time treatments. Nutrients were better removed in treatments with plants (DOC 68% and 72%; NH 4-N 92% and 95%; TKN 65% and 62%; PO 4-P 79% and 72%; TP 67% and 52% for 10-day HRT; 5-day HRT treatments). In the unplanted treatments, negative values were achieved in the removal of phosphate in wastewater and the presence of plants could further polish the wastewater so phosphate concentrations decreased in the planted treatments. The effluent concentrations in the planted treatments meet the Inland Water A effluent standard, and they can be used in recreation park in Hong Kong (1 mg L −1 of NO x; 15 mg L −1 of NH 3; 1 mg L −1 of TP).

Removal of phosphate from water by a highly selective La(III)-chelex resin

A new polymer ligand exchanger (PLE) has been developed for the removal of phosphate in wastewater. This PLE, consisting of lanthanum(III) bound to chelex-100 resin, was prepared by passing LaCl 3 solution through a column of chelex-100. Uptake of phosphate from water by this La-chelex resin was investigated in the column mode. The La-chelex resin was able to remove phosphate efficiently from water, and the uptake of phosphate was not affected by the presence of large amounts of anions (0.1 M) such as chloride and sulfate. The La-chelex resin was also able to efficiently remove phosphate from seawater to <0.1 mg-P l −1, and regenerated for reuse by removing the sorbed phosphate by eluting with 6 M HCl.