Anionic Polyacrylamide Research Articles

Concentration effects of calcium ion on polyacrylamide fouling of ion-exchange membrane in electrodialysis treatment of flue gas desulfurization wastewater

Residual anion polyacrylamide (APAM) and fluctuating calcium ion (Ca2+) in flue gas desulfurization wastewater after pretreatment could result in ion-exchange membrane fouling during electrodialysis process. Concentration effects of Ca2+ on APAM fouling were systematically investigated and the mechanisms were illustrated. Results of desalination performance indicated that Ca2+ alleviated APAM fouling and the mitigating effect increased firstly and then declined, obtaining the mildest fouling phenomenon in the presence of 1.0 mM Ca2+. Zeta potential and particle radius of APAM in the feed solutions increased as Ca2+ changed the charge balance of APAM molecules and complexed with them. Morphology and chemical structure analysis concluded that APAM molecules were adsorbed on the membrane surface and the fouled layer changed with increasing Ca2+ concentration, from dense layer to reticular structure and then to sophisticated multilayer structure. Calculation of interfacial free energy based on Extended Derjaguin-Landau-Verwey-Overbeek theory confirmed that electrostatic interaction dominated the membrane fouling process. Concentration effects of Ca2+ were more remarkable on membrane-APAM attraction and APAM-APAM repulsion at 0.0–1.0 and 1.0–10.0 mM, respectively. The results contribute to establishing comprehensive understanding of the concentration effects of Ca2+ on polymer fouling of membranes and provide new insights into cleaning process optimization.

Synthesis of antibacterial polyaluminium silicate sulfate /sepiolitenano composite coagulant for oilfield sewage treatment

The utilization of a large amount of anionic polyacrylamide (APAM) and sodium alkyl benzene sulfonate can induce the emulsified oil to acquire a stable emulsified colloid system in polymer flooding oily wastewater. However, for the traditional inorganic coagulants, such as polyaluminum, polyiron, etc., a relatively large number of bacteria will breed after oily sewage is treated for a specific period of time. Along these lines, in work, a new type of antibacterial polymeric aluminum silicate sulfate/sepiolite coagulant (PASS-H) was synthesized by using grafting hydrophobic antibacterial monomers in combination with coagulants composed of sepiolite as the base material for improving oily sewage purification. The structure and the surface morphology of the copolymer were systematically characterized, indicating that PASS-H was successfully synthesized. In addition, the coagulation performance of the polyaluminum silicate sulfate (PASS), modified sepiolite, and PASS-H during the treatment of polymer-containing oily wastewater was compared. In the coagulation experiments, PASS-H exhibited excellent turbidity, oil removal, and antibacterial properties. At 60 mg/L, the turbidity, oil removal rate, Zeta potentialand maximum floc size were 98%, 95%, 1.59 mv, and 26 μm, respectively. The mechanism of coagulation was thoroughly investigated based on the order of dosing, the tested water pH, Zeta potential, floc size, and the impact of the floc morphology on the coagulation. The coagulation behavior of the separate addition of the modified sepiolite and PASS was weaker than that induced by the one-time addition of PASS-H. Moreover, the enhanced charge neutralization, bridging adsorption, sweeping, and adsorption played a synergistic role in reducing the total amount of PASS-H and improving the coagulation ability. The introduction of antimicrobial monomers in PASS-H can also effectively inhibit the regeneration of sulfate-reducing bacteria (SRB) in the water. Finally, the residual turbidity and oil removal rate of the different coagulants were statistically analyzed. The extracted results have practical significance for both cost reduction and efficiency increase in large-scale applications.

Aerobic degradation of anionic polyacrylamide in oil sands tailings: Impact factor, degradation effect, and mechanism

An investigation was carried out to study the degradation of anionic polyacrylamide (A-PAM) under different temperature and microorganism conditions as well as to assess its effects on water chemistry and toxicity in oil sands tailings. The maximum removal efficiency of A-PAM was 41.0 % in tailings water with augmented microorganisms at 20 °C. No acrylamide (AMD) monomer was released during the A-PAM degradation, while residual AMD, from the manufacturing process to make A-PAM, was completely removed within 4 weeks. Both temperature and microorganisms showed significant effects (p < 0.05) on the degradation of A-PAM and residual AMD. Gel permeation chromatography (GPC) and Fourier transform infrared (FT-IR) analyses showed that biodegradation could be the active pathway for A-PAM degradation in oil sands tailings. These analyses also indicated that macromolecular A-PAM was degraded into lower molecular weight organic compounds. No remarkable changes of the total concentration of naphthenic acids (NAs) were observed in A-PAM treated tailings water. However, low concentrations of fatty acids (<2.5 mg/L), which fit the NAs formula, were detected in pure polymer solution, indicating that A-PAM degradation would not affect the total concentration of NAs in tailings water but affect their distribution. Our results also showed that total organic carbon (TOC) and chemical oxygen demand (COD) could be used as indicators of A-PAM degradation in tailings water due to their strong linear correlations (R2 > 0.90). Only slight increases in zeta potential and pH were found during A-PAM degradation. Limited effect on acute toxicity and no genotoxicity were found in A-PAM treated tailings water. Furthermore, the results suggest that A-PAM undergoes hydrolysis of amide groups by amidase enzymes, releasing ammonia and smaller molecules like organic acids. This research provides valuable information regarding the stability and impacts of A-PAM and thus will be beneficial for the management of oil sands tailings in long period of time.

Preparation of starch-acrylic acid-carboxymethyl cellulose copolymer and its flocculation performance towards methylene blue

Flocculants synthesized from biopolymers show the virtues of low cost, excellent efficiency and environmental friendliness. In this study, starch-acrylic acid-carboxymethyl cellulose (SAC) tertiary anionic copolymers were prepared by graft copolymerization. The optimal synthesis process was determined as raw material ratio of 1:3:1, acrylic acid neutralization degree of 70%, initiator dosage of 1.0 wt%, reaction temperature of 75 °C and reaction time of 5 h according to the flocculation performance towards methylene blue simulated waste water. Results demonstrated that the decolorization ratio of methylene blue (100 mg/L) could be up to 81.3% at the SAC dosage of 350 mg/L. The SAC achieved rapid flocculation kinetics and excellent color removal over a broad range of pH, ambient temperature and ionic strength. Furthermore, the operation cost of SAC is only one-fourth of industrial anionic polyacrylamide. The prepared SAC flocculant is promising for industrial dye wastewater treatment owing to its green raw materials, high efficiency and low operation cost.

Desert silty sand modified by anionic PAM and ordinary portland cement: Microfabric reinforcement and durability

The modification of desert silty sands has been a great challenge due to its relative uniform particle dimension and non-cohesion. This paper presents a study on utilizing a new additive, anionic polyacrylamide (PAM) with ordinary Portland cement (OPC) to modify the desert silty sand. Unconfined compression strength (UCS) tests were conducted to investigate the strength and durability (resistance to cyclic wet-dry and freeze–thaw damage) of modified sands at the maximum dry density; the scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) spectroscopy tests were carried out for microstructural analysis. Results reveal that the PAM fraction has a significant influence on the mechanical performance of the modified desert silty sand, and a threshold PAM dosage exists, beyond which adding excessive PAM will inhibit the strength and durability further. The microstructural analysis reveals that the physical stick-up of the PAM-to-sand particles leads to the formation of the spatial cobweb-like reticular structure. The Ca2+ cation released by OPC served as a cationic bridge, which in turn enhance the PAM adsorption efficiency. However, excessive PAM would play a negative role, chiefly because of the excessive accumulation between the hydrated production and sand particles. This study indicates that the combination of cement and PAM has the virtues of both cement-stabilized and PAM microfabric-reinforced sand. This binary PAM–OPC modification approach plays a more efficient role if a rational PAM incorporation (0.1–0.3 % in this study) is selected.

Printing Ink Wastewater Treatment Using Hydrodynamic Cavitation and Coagulants/Flocculants

Raw printing ink wastewater (PIW) was treated with various inorganic coagulants and organic flocculants (anionic and cationic polyacrylamides). These processes were also examined as post treatment step following hydrodynamic cavitation. Treatment effectiveness was assessed through color, chemical oxygen demand (COD) and total suspended solids (TSS) removal. The addition of 4500 mg L−1 polyaluminum chloride coagulant in undiluted PIW (COD: 17000 mg L−1) resulted in 99% color removal, 96% COD and TSS removal, after settling for 2 h. The addition of 10 mg L−1 of anionic polyacrylamides in the sample reduced settling time to only 5 min, with concomitant 96–98% removal efficiency. The addition of a 4 min hydrodynamic cavitation pretreatment step reduced coagulant addition by 33%, for the treatment of undiluted PIW (with 10 mg L−1 anionic polyacrylamide), while removals were ranged between 96 and 98%. Economic analysis for the undiluted PIW showed that costs were reduced by ca. 20% with the hydrodynamic cavitation pretreatment step. Moreover, sludge characterization showed the presence of maghemite, aluminum chloride and potassium aluminum silicate. Finally, toxicity tests revealed a significant attenuation of the toxic potential of undiluted PIW, thus indicating the enhanced efficiency of the proposed combined process (hydrodynamic cavitation and coagulation/flocculation).

Interaction between PAM and kaolinite (0 0 1) surface in aqueous solution, insights from DFT and MD simulations

Molecular dynamics (MD) simulations and density functional theory (DFT) calculations were performed to investigate the adsorption of cationic polyacrylamide (CPAM), nonionic polyacrylamide (NPAM), and anionic polyacrylamide (APAM) on the kaolinite (001) surface. DFT calculations revealed that O atoms are the active sites for the amide group and anionic group, while the active sites of the cationic group are O atoms and the quaternary ammonium group. The adsorption behaviors have been studied in terms of relative concentration distribution, interaction energy, number density, and self-diffusion coefficient. MD simulations indicated that the order of the adsorption strength and bridging performance is CPAM > NPAM > APAM. However, NPAM is easier to form hydrogen bonds with the atoms on the kaolinite (001) surface compared with CPAM and APAM. Moreover, the electrostatic interaction is the main driving force for the adsorption of the three polyacrylamides on the kaolinite (001) surface. Analysis of the dynamic properties of water indicated that the effect of polyacrylamide adsorption on the wettability of the kaolinite (001) surface showed identical trends as adsorption strength. The simulation results are in good agreement with the experimental data.

Competitive adsorption of Cu2+, Pb2+, Cd2+, and Zn2+ onto water treatment residuals: implications for mobility in stormwater bioretention systems.

The lack of knowledge regarding competitive adsorption of heavy metal ions onto water treatment residuals has been hindering their reuse as a medium in stormwater bioretention systems. Competitive adsorption of copper(II), lead(II), cadmium(II), and zinc(II) onto polyaluminium chloride and anionic polyacrylamide water treatment residuals (PAC-APAM WTRs) was evaluated with different pH, temperature, initial concentration, and time. The competitive adsorption removal increased with the increase of pH and temperature. The analysis of the ratios of maximum adsorption capacity of a heavy metal ionic species in a multi-component system to that in a mono-component system (Qmix/Qmono) demonstrated that the coexisting ion had a negative effect on the adsorption of a metal ionic species. The Langmuir model provided a better fit, indicating that the adsorption could be a monolayer adsorption process. The modified Langmuir isotherm studies showed that the affinity order in the multi-component systems was Cu2+>Pb2+>Cd2+>Zn2+. The pseudo-second-order model better described the adsorption kinetics implying that the competitive adsorption behavior could be interpreted by diffusion-based mechanisms. This study contributed to a better understanding the mobility of those frequently occurring heavy metal ions in stormwater runoff in the PAC-APAM WTRs media layer of stormwater bioretention systems.

Publisher Correction: Transport Behavior of Cu2+ Under Binary and Multi-Component Systems in the Columns of Polyaluminium Chloride and Anionic Polyacrylamide Water Treatment Residuals: Implication for Reuse in Stormwater Bioretention Systems

Publisher Correction: Transport Behavior of Cu2+ Under Binary and Multi-Component Systems in the Columns of Polyaluminium Chloride and Anionic Polyacrylamide Water Treatment Residuals: Implication for Reuse in Stormwater Bioretention Systems

Effect of polyaluminium silicate sulphate with different alkyl chain lengths on oily sewage in oil fields

When the amount of anionic polyacrylamide (APAM) and petroleum sulphonate in polymer-flooding oily sewage increases, a stable emulsification system forms. This makes the treatment of oily sewage increasingly difficult. To better develop high-efficiency coagulants from scratch, this study first determined the structure and carbon number of petroleum sulphonate using 1H NMR and 13C NMR spectroscopy. Then, hydrophobic monomers with different chain lengths were copolymerised with aluminium salts to prepare inorganic polymer coagulants with different hydrophobic association abilities. Three novel coagulants were successfully prepared, as verified by FTIR and hydrodynamic radius detection, and their coagulation mechanism and performance in oily sewage were investigated and compared with (polyaluminium silicate sulphate) PASSi. The particle size and morphology of flocs after the addition of coagulant were detected by laser particle size analysis and scanning electron microscopy. The structure-activity relationship between emulsifiers and coagulants with different chain lengths was studied via the second virial coefficient A2. Polyaluminium silicate sulphate-hexadecyltrimethoxy (PASSi-C16) was determined to have the best coagulation effect by turbidity, oil removal rate and Zeta potential detection. This may have been due to PASSi-C16 containing a similar lipophilic group to the carbon chain structure of petroleum sulphonate, which could easily destroy the emulsion layer. These results provide insights into methods to improve the hydrophobic association capacity and for the targeted use of associative coagulants in large-scale applications.

Effect of surfactant and flocculant on low-rank coal slime filtration: From filter cake characteristics point of view

Filter aids are widely used in low-rank coal (LRC) slime filtration. However, their impact on filter cake characteristics is still unclear. In this paper, the effect of anionic polyacrylamide (APAM) and cetyltrimethylammonium bromide (CTAB) on the filter cake characteristics was investigated using Darcy’s filtration theory and low-field nuclear magnetic resonance (L-F NMR). The slime and filtrate property change was determined by contact angle, XPS, FBRM, Zeta potential and surface tension measurements. The results showed that the filter aid improved slime filtration rate and reduced filter cake moisture. The filter aid effect of APAM was better than that of CTAB. CTAB significantly improved the slime surface hydrophobicity with the contact angle increasing to 90.5°, and reduced the filtrate surface tension to 35.26 mN/m. However, APAM decreased the absolute value of slime Zeta potential by 7.48 mV, and increased the slime floc size by about 7–9 µm. Both CTAB and APAM can reduce the filtration resistance, but the effect of APAM was better than that of CTAB, because APAM greatly improved the filter cake permeability. L-F NMR results showed that CTAB increased the filter cake porosity only by 2.65%, while APAM significantly improved the filter cake porosity by 11.65%, especially the mesopore porosity of cake, which increased by 10.48%. It was indicated that CTAB reduced the filtration resistance by “lubricating” the pore wall of the filter cake, while APAM improved the filter cake porosity and permeability by weakening the electrostatic repulsion between slime particles and promoting floc formation through aggregation effect. This research provided a new perspective to reveal the mechanism of LRC slime filtration.

Study of the coagulation-flocculation treatment of flowback water from shale gas hydraulic fracturing by using combination of dithiocarbamate compound-polyacrylamide

In this paper, a dithiocarbamate-type flocculant DTC-TETA was prepared by using triethylenetetramine as the material and combination of DTC-TETA and polyacrylamide was used for the coagulation-flocculation of flowback water from shale gas hydraulic fracturing (FWSG). The coagulation-flocculation process was optimized by using turbidity as index and the recommended process was as follows: DTC-TETA dosage 200 mg/L, anionic polyacrylamide AN905 dosage 1 mg/L, flocculation stirring speed 200 rpm, flocculation stirring time 3 min and settlement time 5 min. The turbidity of FWSG can be reduced to be 13 NTU from the initial turbidity of more than 2000 NTU under the recommended process. The performance of DTC-TETA was much better than that of polyaluminum chloride and the Fe2+ in FWSG also can be removed. The function mechanism of DTC-TETA was investigated through the studies of zeta potential change of suspended solids and structural characteristics of flocs. The results confirmed that the flocs were developed by the network formed by the coordination reaction between DTC-TETA and Fe2+, which can filter out suspended solids. This study signifies that both suspended solids and Fe2+ ion can be removed by using DTC-TETA as flocculant, which is a new choice for the FWSG treatment.

Cactus Cladode Juice as Bioflocculant in the Flocculation-Thickening Process for Phosphate Washing Plant: A Comparative Study with Anionic Polyacrylamide

In the phosphate industry, the thickening process is vital to increasing the solid slurry concentration and to recovering water that is as clear as possible. The performance of the thickening process depends mainly on the coagulation–flocculation effect. The thickening process is based on flocculant agents to concentrate particles: flotation and washing plant rejects as large flocs, which accelerate their sedimentation velocity. The phosphate industry worldwide uses synthetical flocculants such as polyacrylamides. These flocculants are non-biodegradable, limiting the process efficiency regarding cost and harmful effects on the environment. This study proposes cactus cladodes juice as an eco-friendly alternative to industrial flocculants. The particle size of the phosphate samples ranges from 0 μm to 160 μm, with a solid concentration of 8%. This bioflocculant allowed for an increase in sedimentation velocity of 95% compared with the case without flocculant. The optimal amount of cactus bioflocculant for decanting 1 tonne of phosphate pulp at pH 7–8 is 1.12 kg. Special attention is paid to understanding the flocculation mechanism. The results of the physicochemical characterization show that the flocculant biopolymers have similar characteristics to anionic polyacrylamide. This work indicates the promising application of the cactus juice bioflocculant in phosphate washing plants.

Molecular dynamics studies of hematite surfaces with PAM, HPAM and metasilicate

In the search to improve the obtaining of iron ore, different additives have been proposed to improve this activity. A deeper study is necessary to understand the affinities of different additives on iron ore and thus be able to search for or synthesize new additives according to the desired objective. In this work, the affinities of the iron mineral represented by the hematite crystal on the neutral 001 surfaces at pH ~9 are studied by molecular dynamics methods, in the presence of waters with low salinity and high salinity. The additives to be studied are a sodium metasilicate dispersant, a neutral polyacrylamide (PAM) flocculant, and 25% anionic polyacrylamide (HPAM). The study considered the calculation of the minimum distance between the surface and the additives. The results show that the affinity of the metasilicate is high with the surface. In the case of PAM polymers, their adsorption decreased as the number of salts increased. In the case of HPAM, the adsorption is greater than in PAM and improved with the addition of salts. This indicates that hematite is a surface with a high local charge density that attracts charged groups such as metasilicates and HPAM. the neutral PAM polymer is adsorbed but to a lesser extent due to its neutrality. The presence of salts indicates that there is competition for adsorption on hematite with respect to PAM, but that the salt is beneficial to HPAM due to the formation of cationic bridges. These results will help in the search for additives for the concentration or dispersion of iron ore.

Biodegradation of anionic polyacrylamide by manganese peroxidase: docking, virtual mutation based on affinity, QM/MM calculation and molecular dynamics simulation.

Manganese peroxidase (Mn P) is capable of effectively degrading anionic polyacrylamide (HPAM). However, the interaction of Mn P with HPAM at molecular level is lacking until now. Here, the HPAM model compounds, HPAM-2, HPAM-3, HPAM-4, and HPAM-5, were selected to reveal their binding mechanisms with Mn P. The results showed that the most suitable substrate for Mn P was HPAM-5, and the main reason for MnP-HPAM-5 with maximal affinity was strong hydrogen bond. LYS96 was the important key residue in all complexes, and the number of key residue was largest in MnP-HPAM-5. The optimal THR27ILE mutant may enhance the affinity of Mn P to HPAM-4. The stability of Mn P binding to HPAM-4 was the optimal. These results were helpful in designing highly efficient Mn P against HPAM to protect the ecological environment.

Microfiltration pretreatment of polymer-flooding produced wastewater before desalination: Role of Ca2+ and Mg2+ in membrane fouling

To better control membrane fouling during microfiltration pretreatment of polymer-flooding produced wastewater (PFPW) before desalination, an accurate elaboration of the fouling mechanisms of anionic polyacrylamide (APAM) in high-salinity environments is vital. Herein, the effects of divalent cations (Ca2+ and Mg2+) on APAM-induced membrane fouling were comprehensively investigated. Both Ca2+ and Mg2+ aggravated membrane fouling. The pseudo-stable flux decreased from 0.38/0.38 to 0.35/0.32, 0.28/0.25, 0.23/0.20, and 0.19/0.15 as the ionic strength of Ca2+/Mg2+ increased from 0 to 1000, 2000, 5000, and 10,000 mg/L. Results of fouling resistances, morphology images of fouled membranes, and extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory supported this. In comparison with hydrated Mg2+, the charge density of hydrated Ca2+ is larger, which provides more efficient electrostatic screening. Moreover, Ca2+ can coordinate with APAM carboxylate to form APAM-Ca2+ complexes with a regular porous structure. Consequently, under identical ionic concentration, APAM-Ca2+ could provide weaker osmotic pressure. Accordingly, lower fouling resistances, rejection rates, and higher flux recovery rates were achieved in the case of Ca2+. This study distinguishes the roles of Ca2+ and Mg2+ in microfiltration membrane fouling by polymeric organics, which will be targeted to guide the efficient microfiltration process of PFPW before advanced desalination.

Transport Behavior of Cu2+ Under Binary and Multi-Component Systems in the Columns of Polyaluminium Chloride and Anionic Polyacrylamide Water Treatment Residuals: Implication for Reuse in Stormwater Bioretention Systems

Transport Behavior of Cu2+ Under Binary and Multi-Component Systems in the Columns of Polyaluminium Chloride and Anionic Polyacrylamide Water Treatment Residuals: Implication for Reuse in Stormwater Bioretention Systems

Effect of polyacrylamide on the workability and interlayer interface properties of 3D printed cementitious materials

Weak interlayer interface is a major drawback of three-dimensional (3D) printed cementitious materials technology. In this paper, the effect of anionic polyacrylamide (APAM) with different dosages on the workability, interlayer interface properties (i.e., interlayer durability, shear bond strength) and interface microstructure of 3D printed cement mortar were studied. The relationship between the workability regulated by APAM and the interlayer interface properties was analyzed. The results showed that the interlayer interface properties of printed artifacts had a good correlation with the workability of fresh cement pastes. With the increase of APAM content, the plastic viscosity and structural build-up rate of cement paste improved. Meanwhile, the interface microstructure defects increased, and the porosity became higher, hence resulting in the decline of the interlayer durability and shear bond strength. In addition, the introduction of APAM can improve the cohesiveness and layer stacking performance of 3D printed cement mortar.

Hydration, mechanical properties, and microstructural characteristics of cement pastes with different ionic polyacrylamides: A comparative study

Polyacrylamides (PAMs) have been widely used as chemical admixtures to modify the workability of cement-based materials. However, polymers possess variable molecular characteristics that have different effects on the macro- and micro-properties of cement, which need to be further explored. In this study, three different ionic PAMs, namely anionic PAM (APAM), cationic PAM (CPAM), and nonionic PAM (NPAM), were applied to investigate their effects on the hydration and mechanical properties of Portland cement. Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) tests were carried out to reveal the evolution of cement phase compositions. The results indicate that APAM significantly delays the cement hydration, increases the cement drying shrinkage, and reduces the cement strength development. However, CPAM and NPAM promote total heat release from the cement. CPAM and NPAM have minor effects on the cement drying shrinkage and strength development compared with APAM. Phase composition analysis reveals that APAM inhibits the dissolution of C3S and promotes the formation of Ca(OH)2 after 1 d. In contrast, CPAM and NPAM mainly enhance the dissolution of C3S before 4 h.

Preparation of humic acid-bentonite polymer composite: A heavy metal ion adsorbent

Adsorbents for wastewater treatment have evolved from scientific adsorbents to natural adsorbents. In this study, a humic acid-bentonite polymer (HBP) composite comprising humic acid, bentonite, and anionic polyacrylamide was integrated into an anionic polyacrylamide (aPAM) polymer matrix as an adsorbent pellet with N, N-methylene-bis-acrylamide (MBA), sodium tetraborate pentahydrate and chromium chloride is used as a novel adsorbent to remove Ni2+, Cd2+ and Pb2+ ions from aqueous solution. Sorption of these ions onto HBP is studied as a function of pH, adsorbent dosage, initial metal ion concentration, humic acid, and bentonite properties to evaluate adsorption efficiency. The results showed that adsorption sharply depends on pH, metal ion concentration, and contact time, but is complemented by humic acid and bentonite properties. The adsorption increased from 8% to 94.7% in the first 30 min at respective pH values of 5.6 and 9 for (Ni2+, Cd2+, and Pb2+). The HBP sorption power decreased with increasing adsorbent dosage, while the adsorption efficiency increased in ascending order for the cations Pb2+, Ni2+ and Cd2+ with efficiencies up to 94.7%, 90.9%, and 90.2%. The experimental data for Ni2+, Pb2+ adsorption fits the Langmuir isotherm, while that for Cd2+ adsorption fits the Freundlich isotherm. HBP showed modest adsorption performance at low and high concentrations, this is attributed in large part to the humic acid and bentonite properties that affect HBP's unique performance.