Application of Zirconium/PVA Modified Flat-Sheet PVDF Membrane for the Removal of Phosphate from Aqueous Solution

Removal of phosphorus by modified bentonite:polyvinylidene fluoride membrane-study of adsorption performance and mechanism

Enhanced phosphorus management, geared towards sustainability, is imperative due to its indispensability for all life forms and its close association with water bodies' eutrophication, primarily stemming from anthropogenic activities. In response to this concern, innovative technologies rooted in the circular economy are emerging, to remove and recover this vital nutrient to global food production. This research undertakes an evaluation of the dead-end filtration performance of a mixed matrix membrane composed of modified bentonite (MB) and polyvinylidene fluoride (PVDF) for efficient phosphorus removal from water media. The MB:PVDF membrane exhibited higher permeability and surface roughness compared to the pristine membrane, showcasing an adsorption capacity (Q) of 23.2 mgP·m-2. Increasing the adsorbent concentration resulted in a higher removal capacity (from 16.9 to 23.2 mgP·m-2) and increased solution flux (from 0.5 to 16.5 L·m-2·h-1) through the membrane. The initial phosphorus concentration demonstrates a positive correlation with the adsorption capacity of the material, while the system pressure positively influences the observed flux. Conversely, the presence of humic acid exerts an adverse impact on both factors. Additionally, the primary mechanism involved in the adsorption process is identified as the formation of inner-sphere complexes.

Egg White-Mediated Fabrication of Mg/Al-LDH-Hard Biochar Composite for Phosphate Adsorption

Phosphorus is one of the main causes of water eutrophication. Hard biochar is considered a promising phosphate adsorbent, but its application is limited by its textural properties and low adsorption capacity. Here, an adhesion approach in a mixed suspension containing egg white is proposed for preparing the hybrid material of Mg/Al-layered double hydroxide (LDH) and almond shell biochar (ASB), named L-AE or L-A (with or without egg white). Several techniques, including XRD, SEM/EDS, FTIR and N2 adsorption/desorption, were used to characterize the structure and adsorption behavior of the modified adsorbents. The filament-like material contained nitrogen elements at a noticed level, indicating that egg white was the crosslinker that mediated the formation of the L-AE hybrid material. The L-AE had a higher phosphate adsorption rate with a higher equilibrium adsorption capacity than the L-A. The saturation phosphate adsorption capacity of L-AE was nearly three times higher than that of L-A. Furthermore, the number of surface groups and the density of the positively charged surface sites follow the ASB < L-A < L-AE order, which is consistent with their phosphate adsorption performance. The study may offer an efficient approach to improving hard biochar’s adsorption performance in wastewater treatment.

Evaluation of phosphate adsorption by porous strong base anion exchangers having hydroxyethyl substituents: kinetics, equilibrium, and thermodynamics

Phosphate anions are recognized as the main responsible for the eutrophication of surface waters. In this work, two strong base anion exchangers having either N,N-dimethyl 2-hydroxyethylammonium (SBAEx.2M) or N,N-diethyl 2-hydroxyethylammonium (SBAEx.2E) functional groups, as highly efficient sorbents in the removal of phosphate anions, are presented. The influence of the main parameters (pH, contact time, initial concentration of phosphate, temperature) on the adsorption performances was investigated in batch mode. Modeling the kinetics data by Lagergren, Ho and McKay, and Elovich kinetic models indicated chemisorption as the main mechanism of sorption. The sorption at equilibrium was modeled with Langmuir, Freundlich, Sips, Dubinin-Radushkevich, and Temkin isotherm models. The experimental isotherms were the best fitted by Langmuir and Sips isotherms, the maximum sorption capacity for phosphate anions being 233.88 mg g^-1 SBAEx.2M and 223.5 mg g^-1 SBAEx.2E, at pH 3, and 23 °C. Adsorption of phosphate anions in competitive conditions showed that the interference with co-existing anions was low in the case of Cl^- ions and much higher with SO₄^2- ions, the ion exchange having an important contribution in the adsorption process. The adsorption was spontaneous and endothermic, the degree of spontaneity increasing with the increase of temperature. The high level of reusability, the adsorption capacity decreasing with only ~ 7% in the case of SBAEx.2E and with ~ 9% in the case of SBAEx.2M, after five sorption/desorption cycles, recommends these SBAEx as promising adsorbents for phosphate removal.

Cytotoxic aquatic pollutants and their removal by nanocomposite-based sorbents

Water is an extremely essential compound for human life and, hence, accessing drinking water is very important all over the world. Nowadays, due to the urbanization and industrialization, several noxious pollutants are discharged into water. Water pollution by various cytotoxic contaminants, e.g. heavy metal ions, drugs, pesticides, dyes, residues a drastic public health issue for human beings; hence, this topic has been receiving much attention for the specific approaches and technologies to remove hazardous contaminants from water and wastewater. In the current review, the cytotoxicity of different sorts of aquatic pollutants for mammalian is presented. In addition, we will overview the recent advances in various nanocomposite-based adsorbents and different approaches of pollutants removal from water/wastewater with several examples to provide a backdrop for future research.

Improvement of Ultrafiltration for Treatment of Phosphorus-Containing Water by a Lanthanum-Modified Aminated Polyacrylonitrile Membrane

Phosphorus contamination in fresh water has posed a great risk to aquatic ecosystems and human health due to extensive eutrophication. In this paper, we are reporting a lanthanum (La)-modified aminated polyacrylonitrile (PAN) adsorptive membrane for effective decontamination of phosphorus from the simulated water. The PAN membrane was first aminated to introduce the amine group as an active site for La and then followed by the in situ precipitation of La particles. The kinetics study showed that the rapid adsorption occurred within the initial 4 h with the equilibrium established at 8 h. The membrane worked well in the acidic pH region, with optimal pH 4 and 5 without and with the pH control, respectively. The maximum adsorption capacities were 50 and 44.64 mg/g at pH 5 and 7, respectively. The adsorption of phosphorus was not affected by the existence of commonly existing anions except fluorides in water. In the filtration study, it was observed that the removal of phosphorus remained the optimum, although the operating pressure was increased from 1 to 3 bar. The modified membrane was able to treat 0.32 L of a 10 mg/L phosphate solution to meet the maximum allowable limit of 0.15 mg/L for the trade effluent. The mechanism study revealed that the removal was primarily associated with the ion exchange between a phosphorus ion and a hydroxyl group from the La particles.

Effect of precipitation pH and coexisting magnesium ion on phosphate adsorption onto hydrous zirconium oxide

To understand the effect of precipitation pH and coexisting Mg²⁺ on phosphate adsorption onto zirconium oxide (ZrO₂), ZrO₂ particles precipitated at pH 5.3, 7.1 and 10.5, i.e., ZrO₂(5.3), ZrO₂(7.1) and ZrO₂(10.5), respectively were prepared and characterized, then their adsorption performance and mechanism in the absence and presence of Mg²⁺ were comparatively investigated in this study. The results showed that the Elovich, pseudo-second-order and Langmuir isotherm models correlated with the experimental data well. The adsorption mechanism involved the complexation between phosphate and zirconium. Coexisting Mg²⁺ slightly inhibited the adsorption of phosphate on ZrO₂(5.3), including the adsorption capacity and rate, but coexisting Mg²⁺ greatly increased the adsorption capacity and rate for ZrO₂(7.1) and ZrO₂(10.5). The enhanced adsorption of phosphate on ZrO₂(7.1) and ZrO₂(10.5) in the presence of Mg²⁺ was mainly due to the formation of Mg²⁺-HPO₄^2- ion pair (MgHPO₄⁰) in the solution and then the adsorption of MgHPO₄⁰ on the adsorbent surface, forming the phosphate-bridged ternary complex Zr(OPO₃H)Mg. In the absence of Mg²⁺, the maximum phosphate adsorption capacity at pH 7 calculated from the Langmuir isotherm model decreased in the order of ZrO₂(7.1) (67.3 mg/g) > ZrO₂(5.3) (53.6 mg/g) ≈ ZrO₂(10.5) (53.1 mg/g), but it followed the order of ZrO₂(7.1) (97.0 mg/g) > ZrO₂(10.5) (79.7 mg/g) > ZrO₂(5.3) (51.3 mg/g) in the presence of Mg²⁺. The results of this work suggest that ZrO₂(7.1) is more suitable for use as an adsorbent for the effective removal of phosphate from municipal wastewater than ZrO₂(5.3) and ZrO₂(10.5), because Mg²⁺ is generally present in this wastewater.

Development of novel polysulfone membranes with embedded zirconium sulfate-surfactant micelle mesostructure for phosphate recovery from water through membrane filtration

We prepared novel membranes that could adsorb phosphate from water through membrane filtration for use in a phosphate recovery system. Zirconium sulfate surfactant micelle mesostructure (ZS), which was the phosphate adsorbent, was embedded in a polysulfone matrix and flat sheet ultrafiltration membranes were made by nonsolvent induced phase separation. Scanning electron microscopy showed that the ZS particles existed on both the top surface and in the internal surface of the membrane. Increases in ZS content led to greater pure water flux because of increases in the surface porosity ratio. The amount of phosphate adsorbed on the membrane made from the polymer solution containing 10.5 wt% ZS was 0.071 mg P/cm² (64.8 mg P/g-ZS) during filtration of 50 mg P/L synthetic phosphate solution. The membrane could be repeatedly used for phosphate recovery after regeneration by filtration of 0.1 M NaOH solution to desorb the phosphate. We applied the membrane to treat the effluent from an anaerobic membrane bioreactor as a real sample and successfully recovered phosphate.