Esterification for butyl butyrate formation using Candida cylindracea lipase produced from palm oil mill effluent supplemented medium

The ability of Candida cylindracea lipase produced using palm oil mill effluent (POME) as a basal medium to catalyze the esterification reaction for butyl butyrate formation was investigated. Butyric acid and n-butanol were used as substrates at different molar ratios. Different conversion yields were observed according to the affinity of the produced lipase toward the substrates. The n-butanol to butyric acid molar ratio of 8 and lipase concentration of 75 U/mg gave the highest butyl butyrate formation of 63.33% based on the statistical optimization using face centered central composite design (FCCCD) after 12 h reaction. The esterification potential of the POME based lipase when compared with the commercial lipase from the same strain using the optimum levels was found to show a similar pattern. It can be concluded therefore that the produced lipase possesses appropriate characteristics to be used as a biocatalyst in the esterification reactions for butyl butyrate formation.     

Applications of Fenton oxidation processes for decontamination of palm oil mill effluent: A review

Oil palm agro-industry is a major revenue earner for Malaysia with the country being one of the major producers of crude palm oil (CPO) and oil palm products. Its growth has, however, led to massive water consumption and high generation of highly polluting palm oil mill effluent (POME). The inadequacies of ponding system adopted by most palm oil mills (POMs) for the treatment of POME to alleviate environmental and public health concerns are quite alarming. Fenton advanced oxidation technologies are a current research area providing viable alternatives for POME treatment, recovery and managing high demand for water. Its major setback is the generation of a large amount of unwanted sludge of iron (III) complexes thus increasing the costs of sludge management, treatment, and disposal. The salient and promising features of this technique for industrial applications motivate researchers to find ways to overcome its inherent drawbacks. This brief review aimed at discussing and evaluating the performances of the various Fenton oxidation processes, including homogeneous, heterogeneous, photo-Fenton, electro-Fenton, sono-Fenton etc., for POME treatment. Discussions on the future direction of these Fenton processes points towards the utilization of abundant magnetically separable heterogeneous composites as catalysts with high stability, activity, recyclability, and cost-effectiveness for decontamination of POME and other agro-industrial effluents from recalcitrant organic pollutants. The low deployment of such composite catalyst coupled with scarce literature on POME treatment in this regard offers a vast opportunity for research exploration.     

Paper mill sludge-soil mixture: kinetic and thermodynamic tests of cadmium and lead sorption capability

Paper mill sludge (characterized by 29.0% of organic substances such as cellulose, lignin and tannins and 71.0% of inorganic substances such as kaolinite and carbonates) was studied in a mixture with soil in order to evaluate its effects on soil capability for retaining heavy metals. Attention was focused on cadmium and lead sorption and two parameters were investigated, the contact time of paper mill sludge-soil mixture and the paper mill sludge-soil ratio in the mixture. Results showed that paper mill sludge and soil interact to form ‘new’ sorbing sites. Taking into account sorption results of lead, the retention of which by soil is substantially increased by sludge addition, can highlight this modification. Also, the amount of sorbed cadmium was increased by sludge addition.     

Adsorption of cadmium ions from aqueous solutions using nano-montmorillonite: kinetics,isotherm and mechanism evaluations

With increasing industrial development, heavy metal pollution, e.g., cadmium (Cd) pollution, is increasingly serious in soil and water environments. This study investigated the sorption performance of nano-montmorillonite (NMMT) for Cd ions. Adsorption experiments were carried out to examine the effects of the initial metal ion concentration (22.4–224 mg/L), pH (2.5–7.5), contact time (2–180 min) and temperature (15–40 °C). A simulated acid rain solution was prepared to study the desorption of Cd adsorbed on NMMT. After the adsorption or desorption process, the supernatant was analyzed using a flame atomic absorption spectrometry method. The Cd removal rate increased as the pH and contact time increased but decreased as the initial metal ion concentration increased. The maximum adsorption capacity was estimated to be 17.61 mg/g at a Cd²⁺ concentration of 22.4 mg/L. The sorption process can be described by both the Langmuir and Freundlich models, and the kinetic studies revealed that the pseudo-second-order model fit the experimental data. The Cd desorption rate when exposed to simulated acid rain was less than 1%. NMMT possesses a good adsorption capacity for Cd ions. Additionally, ion exchange was the main adsorption mechanism, but some precipitation or surface adsorption also occurred.     

Bioremediation strategies of palm oil mill effluent and landfill leachate using microalgae cultivation: An approach contributing towards environmental sustainability

Palm oil mill effluent (POME) is defined as the wastewater that contains high concentrations of organics, nutrients and oil and grease generated from the production process of palm oil. Therefore, proper discharge and management of POME is important to avoid deleterious impact on the environment. In fact, solid waste generation is a precursor for its disposal issues as most of the solid waste generated in developing nations is dumped into landfills. This has led to the threat posed by the generation of landfill leachate (LL). LL is a complex dark coloured liquid consisting of organic matter, inorganic substances, trace elements and xenobiotics. Hence, it is essential to effectively treat the landfill leachate before discharging it to avoid contamination of soil, surface & groundwater bodies. Conventional treatment methods comprises of physical, biological and chemical treatment, however, microalgal-based treatment could also be incorporated. Furthermore, with the benefits offered by microalgae in valorisation, the application of microalgae in POME and leachate treatment as well as biofuel production, is considerably viable. This paper provides an acumen of the microalgae-based treatment of POME and LL, integrated with biofuel production in a systematic and critical manner. The pollutants assimilation from wastewater and CO₂ biosequestration are discussed for environmental protection. Cultivation systems for wastewater treatment with simultaneous biomass production and its valorisation, are summarised. The study aims to provide insight to industrial stakeholders on economically viable and environmentally sustainable treatment of wastewaters using microalgae, and eventually contributing to the circular bioeconomy and environmental sustainability.     

Removal of Cd(II), Cu(II), and Pb(II) by adsorption onto natural clay: a kinetic and thermodynamic study

In this work, we study the elimination of three bivalent metal ions (Cd²⁺, Cu²⁺, and Pb²⁺) by adsorption onto natural illitic clay (AM) collected from Marrakech region in Morocco. The characterization of the adsorbent was carried out by X-ray fluorescence, Fourier transform infrared spectroscopy and X-ray diffraction. The influence of physicochemical parameters on the clay adsorption capacity for ions Cd²⁺, Cu²⁺, and Pb²⁺, namely the adsorbent dose, the contact time, the initial pH imposed on the aqueous solution, the initial concentration of the metal solution and the temperature, was studied. The adsorption process is evaluated by different kinetic models such as the pseudo-first-order, pseudo-second-order, and Elovich. The adsorption mechanism was determined by the use of adsorption isotherms such as Langmuir, Freundlich, and Temkin models. Experiments have shown that heavy metals adsorption kinetics onto clay follows the same order, the pseudo-second order. The isotherms of adsorption of metal cations by AM clay are satisfactorily described by the Langmuir model and the maximum adsorption capacities obtained from the natural clay, using the Langmuir isotherm model equation, are 5.25, 13.41, and 15.90 mg/g, respectively for Cd(II), Cu(II), and Pb(II) ions. Adsorption of heavy metals on clay is a spontaneous and endothermic process characterized by a disorder of the medium. The values of ΔH are greater than 40 kJ/mol, which means that the interactions between clay and heavy metals are chemical in nature.     

The use of starch‐modified magnetic Fe0 nanoparticles for naphthalene adsorption from water samples: Adsorption isotherm,kinetic and thermodynamic studies

This study was aimed at investigating the effectiveness of starch‐modified magnetic nanoparticles for the removal of naphthalene, which is a polycyclic aromatic hydrocarbon present in the majority of water sediments, from water resources. Magnetic Fe⁰ nanoparticles have recently been considered because of their high efficiency for contaminant removal. In the present study, Fe⁰ nanoparticles were synthesized using sulfate method and starch was used as a stabilizer. The size of the Fe⁰ nanoparticles was measured as approximately 45 nm using X‐ray diffraction and scanning electron microscopy analyses. The removal efficiency of naphthalene from water using the nanoparticles was evaluated based on various factors including the viscosity of naphthalene dissolved in water, and operation factors such as nanoparticle dosage, contact time, initial naphthalene concentration and pH in non‐continuous reactors were optimized. The results revealed that the starch‐modified nanoparticles have high efficiency for removal of dissolved naphthalene from aqueous solution. Under the optimum conditions, more than 99% of naphthalene at a pH of 5.0 with nanoparticle dosage of 0.05 g was removed from aqueous solution in 5 min. The equilibrium adsorption data were interpreted in terms of Langmuir, Freundlich and Temkin isotherm models and the goodness of fit was inspected using linear regression analysis. Our results indicated that the Langmuir model with maximum adsorption capacity was best fitted, suggesting monolayer adsorption. Moreover, it was found that the adsorption process followed the pseudo‐second‐order kinetic model. In addition, a thermodynamic study indicated that the adsorption process of naphthalene from aqueous solution by the starch‐modified nanoparticles was spontaneous and exothermic.     

Utilization of agro-resources by radiation treatment -production of animal feed and mushroom from oil palm wastes

The production of animal feeds and mushrooms from oil palm cellulosic wasres by radiation and fermentation has been investigated in order to utilize the agro-resources and to reduce the smoke pollution. The process is as follows: decontamination of microorganisms in fermentation media of empty fruit bunch of oil palm (EFB) by irradiation, inoculation of useful fungi, and subsequently production of proteins and edible mushrooms. The dose of 25 kGy was required for the sterilization of contaminating bacteria whereas the dose of 10 kGy was enough to eliminate the fungi. Among many kinds of fungi tested, C. cinereus and P. sajor-caju were selected as the most suitable microorganism for the fermentation of EFB. The protein content of the product increased to 13 % and the crude fiber content decreased to 20% after 30 days of incubation with C. cinereus at 30°C in solid state fermentation. P. sajor-caju was suitable for the mushroom production on EFB with rice bran.     

On the Adsorption of Some Catechol Derivatives from Aqueous Solutions onto Activated Carbon Cloth: Equilibrium and Kinetic Studies

The removal of some of pollutants including catechol, 3-methylcatechol, 3-methoxycatechol, and 2,3-dihydroxybenzoic acid by adsorption onto activated carbon cloth (ACC) at 35.0 ± 0.1°C was investigated. The equilibrium experimental data were fitted to Langmuir, Freundlich, Temkin, Langmuir-Freundlich, and Redlich-Peterson isotherms. Also the kinetic experimental data were fitted to the pseudo-first-order and pseudo-second-order kinetic models. It was found that the pseudo-second-order model describes the kinetic of adsorption better than the other one. By comparing the obtained results with the previously reported data, it can be concluded that ACC is a high efficient adsorbent for removal of phenolic compounds from aqueous solutions.     

Sawdust for the Removal of Heavy Metals from Water: A Review

The threat of the accumulation of heavy metals in wastewater is increasing, due to their abilities to inflict damage to human health, especially in the past decade. The world’s environmental agencies are trying to issue several regulations that allow the management and control of random disposals of heavy metals. Scientific studies have heavily focused on finding suitable materials and techniques for the purification of wastewaters, but most solutions have been rejected due to cost-related issues. Several potential materials for this objective have been found and have been compared to determine the most suitable material for the purification process. Sawdust, among all the materials investigated, shows high potential and very promising results. Sawdust has been shown to have a good structure suitable for water purification processes. Parameters affecting the adsorption mechanism of heavy metals into sawdust have been studied and it has been shown that pH, contact time and several other parameters could play a major role in improving the adsorption process. The adsorption was found to follow the Langmuir or Freundlich isotherm and a pseudo second-order kinetic model, meaning that the type of adsorption was a chemisorption. Sawdust has major advantages to be considered and is one of the most promising materials to solve the wastewater problem.     

Evaluation of tetracycline removal by magnetic metal organic framework from aqueous solutions: Adsorption isotherm,kinetics, thermodynamics,and Box-Behnken design optimization

In our current research, an intriguing magnetic nano sorbent Fe₃O₄@Zr-MOF was synthesized in the lab. We used this adsorbent for successfully removing tetracycline (TC) from water. We performed a number of experiments and studies to further support this, including the following: vibrating sample magnetometer (VSM), Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller surface area (BET). Our studies have determined that the Fe₃O₄@Zr-MOF boasts a considerable surface area of 868 m²/g with the highest adsorption capacity (q_max) of 942.12 mg/g. Study the factors that effect on adsorption process such as pH, TC concentration, adsorbent dose, and temperature. The adsorption isotherm was fitted to the Langmuir equation, whereas the kinetic isotherm to the pseudo-second-order equation. The adsorption process was chemisorption as well as the adsorption energy was 20 kJ/mol. Adsorption thermodynamics indicated that the adsorption process was both endothermic and spontaneous. As temperatures increased, the amounts of materials absorbed also increased. The Fe₃O₄@Zr-MOF has magnetic properties as it easily to remove from the solution after adsorption process. The adsorbent was used for five cycles with high efficiency and without change in the chemical composition as well as the XRD was the same before and after reusability. The mechanism of the interaction between Fe₃O₄@Zr-MOF and TC was expected on: Electrostatic interaction, π-π interaction, hydrogen bonding, and pore filling. The adsorption results were optimized using Box Behnken-design (BBD).     

Highly removal of anionic dye from aqueous medium using a promising biochar derived from date palm petioles: Characterization,adsorption properties and reuse studies

The present work investigates the preparation of promising biochar derived from date palm petioles powder (DPB) via a thermal treatment. DPB was characterized through various techniques to analyze the chemical (FTIR), morphological (SEM) and point of zero charges to investigate changes incorporated through the pyrolysis process.The adsorption of methyl orange (MO) onto the biochar was investigated using batch experiments according to different parameters which influence the adsorption process such as: initial dye concentration, equilibrium time, pH, and temperature. Isothermal and reuse studies of MO adsorption onto DPB were also investigated.Results of MO removal on DPB have demonstrated that the adsorption process was initial dye concentration-dependent, and equilibrium time was occurred in 60 min. The biochar presented high stability of MO adsorption capacity in a large domain of pH. Thermodynamic analysis of this process revealed that methyl orange adsorption was exothermic and spontaneous in nature.The experimental data were analyzed by pseudo-first-order, pseudo-second-order model, and the intraparticle-diffusion for kinetics and Langmuir, Freundlich, and Temkin models for isotherms.Kinetic adsorption followed the pseudo-second-order model and the intraparticle-diffusion within pores controlled the adsorption rate. The experimental data yielded good fits with in the following isotherms order: Langmuir > Temkin > Freundlich, The maximum adsorption capacity of MO on DPB was found 461 mg.g^?1. The reusability study reveals the possibility of the reuse of DPB for three (03) cycles of adsorption–desorption, a slight decrease in the ability of methyl orange adsorption has noticed with the increase of the number of adsorption–desorption cycles : 81.03 %, 67.84 %, and 51.72 %, respectively. The found results of the present study show that the biochar derived from date palm petioles have the potential to be used as a promising adsorbent for the treatment of MO dye.     

油页岩飞灰对重金属离子的吸附动力学及热力学

采用批式振荡吸附法研究了燃油页岩电厂循环流化床锅炉飞灰对重金属离子Pb²+、Cu²+、Zn²+、Cd²+的吸附动力学及吸附热力学特性,并提出了吸附机理。结果表明,油页岩飞灰对Pb²+、Cu²+、Zn²+、Cd²+的吸附平衡数据符合Langmuir和Freundlich吸附等温方程,但Freundlich方程能够更好地描述吸附等温线。在油页岩飞灰对重金属离子吸附的初始阶段,拉格朗日准一级动力学方程、准二级动力学方程、Elovich方程、粒子内扩散模型均能很好地反映吸附模式,而整个吸附过程则遵循二级反应动力学方程,其吸附过程是液膜扩散和粒子内扩散共同作用的结果。油页岩飞灰对Pb²+、Cu²+、Zn²+、Cd²+的吸附是吸热反应。     

Synthesis of Nanosilica for the Removal of Multicomponent Cd2+ and Cu2+ from Synthetic Water: An Experimental and Theoretical Study

Copper and cadmium ions are among the top 120 hazardous chemicals listed by the Agency for Toxic Substances and Disease Registry (ATSDR) that can bind to organic and inorganic chemicals. Silica is one of the most abundant oxides that can limit the transport of these chemicals into water resources. Limited work has focused on assessing the applicability of nanosilica for the removal of multicomponent metal ions and studying their interaction on the surface of this adsorbent. Therefore, this study focuses on utilizing a nanosilica for the adsorption of Cd²⁺ and Cu²⁺ from water. Experimental work on the single- and multi-component adsorption of these ions was conducted and supported with theoretical interpretations. The nanosilica was characterized by its surface area, morphology, crystallinity, and functional groups. The BET surface area was 307.64 m²/g with a total pore volume of 4.95×10−3 cm³/g. The SEM showed an irregular amorphous shape with slits and cavities. Several Si–O–Si and hydroxyl groups were noticed on the surface of the silica. The single isotherm experiment showed that Cd²⁺ has a higher uptake (72.13 mg/g) than Cu²⁺ (29.28 mg/g). The multicomponent adsorption equilibrium shows an affinity for Cd²⁺ on the surface. This affinity decreases with increasing Cu²⁺ equilibrium concentration due to the higher isosteric heat from the interaction between Cd and the surface. The experimental data were modeled using isotherms for the single adsorption, with the Freundlich and the non-modified competitive Langmuir models showing the best fit. The molecular dynamics simulations support the experimental data where Cd²⁺ shows a multilayer surface coverage. This study provides insight into utilizing nanosilica for removing heavy metals from water.     

Optimizing adsorptive removal of malachite green and methyl orange dyes from simulated wastewater by Mn‐doped CuO‐Nanoparticles loaded on activated carbon using CCD‐RSM: Mechanism,regeneration, isotherm,kinetic, and thermodynamic studies

In the present work, Mn‐doped CuO‐NPs‐AC was prepared by a simple method, characterized using various techniques such as FESEM, EDX, XRD, PSD, and pH_pzc and finally used for the adsorption of malachite green (MG) and methyl orange (MO) in a number of single and binary solutions. A series of adsorption experiments were conducted to investigate and optimize the influence of various factors (such as different pH, concentration of MG and MO, adsorbent mass, and sonication time) on the simultaneous adsorption of MG and MO using response surface methodology. Under optimal conditions of pH 10, adsorbent dose of 0.02 g, MG concentration of 30 mg L^?1, MO concentration of 30 mg L^?1, and sonication time of 4.5 min at room temperature, the maximum predicted adsorption was observed to be 100.0%, for both MG and MO, showing that there is a favorable harmony between the experimental data and model predictions. The adsorption isotherm of MO and MG by Mn‐doped CuO‐NPs‐AC could be well clarified by the Langmuir model with maximum adsorption capacity of 320.69 mg g^?1 and 290.11 mg g^?1 in the single solution and 233.02 mg g^?1 and 205.53 mg g^?1 in the binary solution by 0.005 g of adsorbent mass for MG and MO, respectively. Kinetic studies also revealed that both MG and MO adsorption were better defined by the pseudo‐second order model for both solutions. In addition, the thermodynamic constant studies disclosed that the adsorption of MG and MO was likely to be influenced by a physisorption mechanism. Eventually, the reusability of the Mn‐doped CuO‐NPs‐AC after six times showed a reduction in the adsorption percentage of MG and MO.     

Cross-Linked Ionic Liquid Polymer for the Effective Removal of Ionic Dyes from Aqueous Systems: Investigation of Kinetics and Adsorption Isotherms

In the current study, we have synthesized an imidazolium based cross-linked polymer, namely, 1-vinyl-3-ethylimidazolium bis(trifluoromethylsulfonyl)imide (poly[veim][Tf₂N]-TRIM) using trimethylolpropane trimethacrylate as cross linker, and demonstrated its efficiency for the removal of two extensively used ionic dyes—methylene blue and orange-II—from aqueous systems. The detailed characterization of the synthesized poly[veim][Tf₂N]-TRIM was performed with the help of ¹H NMR, TGA, FT-IR and FE-SEM analysis. The concentration of dyes in aqueous samples before and after the adsorption process was measured using an UV-vis spectrophotometer. The process parameters were optimised, and highest adsorption was obtained at a solution pH of 7.0, adsorbent dosage of 0.75 g/L, contact time of 7 h and dye concentrations of 100 mg/L and 5.0 mg/L for methylene blue and orange-II, respectively. The adsorption kinetics for orange-II and methylene blue were well described by pseudo-first-order and pseudo–second-order models, respectively. Meanwhile, the process of adsorption was best depicted by Langmuir isotherms for both the dyes. The highest monolayer adsorption capacities for methylene blue and orange-II were found to be 1212 mg/g and 126 mg/g, respectively. Overall, the synthesized cross-linked poly[veim][Tf₂N]-TRIM effectively removed the selected ionic dyes from aqueous samples and provided >90% of adsorption efficiency after four cycles of adsorption. A possible adsorption mechanism between the synthesised polymeric adsorbent and proposed dyes is presented. It is further suggested that the proposed ionic liquid polymer adsorbent could effectively remove other ionic dyes and pollutants from contaminated aqueous systems.     

Adsorptive denitrogenation of indole from model fuel oil over Co-MAC: Adsorption mechanisms and competitive adsorption

The present research article depicts the adsorptive denitrogenation of indole-containing model oil using cobalt-incorporated acid-activated carbon (Co-MAC). The active metal incorporated acetic acid-activated bio-sorbent showed a significant adsorption capacity for indole from model fuel oil than mere activated carbon. In a batch study, maximum 96% indole removal was achieved with an initial indole concentration of 500 mg/L, catalyst dose of 10 g/L, time of 4 h, and reaction temperature of 303 K. The non-linear regression analysis was opted to fit the experimental equilibrium data into various adsorption isotherms, including Langmuir, Freundlich, Temkin and Redlich, and Peterson. Thermodynamic parameters of adsorption were investigated, and the entropy and heat of adsorption change were determined to be 0.26 kJ/mol K and 57.31 kJ/mol, respectively. Besides, a plausible adsorption mechanism of indole was also explored.     

Comparative of the removal of Pb2+, Cd2+ and Ni2+ by nano crystallite hydroxyapatite from aqueous solutions: Adsorption isotherm study

Release of heavy metal onto the water and soil as a result of agricultural and industrial activities may pose a serious threat to the environment. In this study, the adsorption behavior of nano hydroxyapatite with respect to Pb²⁺, Cd²⁺ and Ni²⁺ has been studied in order to consider its application to purity metal finishing wastewater. The batch method has been employed, using metal concentrations in solution ranging from 100 to 400 mg/L. The uptake capacity and distribution coefficients (K_d) were determined for the adsorption system as a function of sorbate concentration. The Langmuir, Freundlich, and Dubinin–Kaganer–Radushkevich (DKR) isotherms applied for sorption studies showed that the amount of metal sorbed on nano hydroxyapatite. It was found that the adsorption phenomena depend on charge density and hydrated ion diameter. According to the equilibrium studies, the selectivity sequence can be given as Pb²⁺ > Cd²⁺ > Ni²⁺. These results show that nano hydroxyapatite holds great potential to remove cationic heavy metal species from industrial wastewater.     

Microwave‐Assisted Synthesis of HKUST‐1 and Functionalized HKUST‐1‐@H3PW12O40: Selective Adsorption of Heavy Metal Ions in Water Analyzed with Synchrotron Radiation

A simple, rapid and efficient synthesis of the metal‐organic framework (MOF) HKUST‐1 [Cu₃(1,3,5‐benzene‐tri‐carboxilic‐acid)₂] by microwave irradiation is described, which afforded a homogeneous and highly selective material. The unusually short time to complete the synthesis by microwave irradiation is mainly attributable to rapid nucleation rather than to crystal growth rate. Using this method, HKUST‐1‐MW (MW=microwave) could be prepared within 20 min, whereas by hydrothermal synthesis, involving conventional heating, the preparation time is 8 h. Work efficiency was improved by the good performance of the obtained HKUST‐1‐MW which exhibited good selective adsorption of heavy metal ions, as well as a remarkably high adsorption affinity and adsorption capacity, but no adsorption of Hg²⁺ under the same experimental conditions. Of particular importance is the preservation of the structure after metal‐ion adsorption, which remained virtually intact, with only a few changes in X‐ray diffraction intensity and a moderate decline in surface area. Synthesis of the polyoxometalate‐containing HKUST‐1‐MW@H₃PW₁₂O₄₀ afforded a MOF with enhanced stability in water, due to the introduced Keggin‐type phosphotungstate, which systematically occluded in the cavities constituting the walls between the mesopores. Different Cu/W ratios were investigated according to the extrusion rate of cooper ions concentration, without significant structural changes after adsorption. The MOFs obtained feature particle sizes between 10–20 μm and their structures were determined using synchrotron‐based X‐ray diffraction. The results of this study can be considered important for potentially wider future applications of MOFs, especially to attend environmental issues.     

Adsorption of Zn2+ from Synthetic Wastewater Using Dried Watermelon Rind (D-WMR): An Overview of Nonlinear and Linear Regression and Error Analysis

Sustainable wastewater treatment is one of the biggest issues of the 21st century. Metals such as Zn²⁺ have been released into the environment due to rapid industrial development. In this study, dried watermelon rind (D-WMR) is used as a low-cost adsorption material to assess natural adsorbents’ ability to remove Zn²⁺ from synthetic wastewater. D-WMR was characterized using scanning electron microscope (SEM) and X-ray fluorescence (XRF). According to the results of the analysis, the D-WMR has two colours, white and black, and a significant concentration of mesoporous silica (83.70%). Moreover, after three hours of contact time in a synthetic solution with 400 mg/L Zn²⁺ concentration at pH 8 and 30 to 40 °C, the highest adsorption capacity of Zn²⁺ onto 1.5 g D-WMR adsorbent dose with 150 μm particle size was 25 mg/g. The experimental equilibrium data of Zn²⁺ onto D-WMR was utilized to compare nonlinear and linear isotherm and kinetics models for parameter determination. The best models for fitting equilibrium data were nonlinear Langmuir and pseudo-second models with lower error functions. Consequently, the potential use of D-WMR as a natural adsorbent for Zn²⁺ removal was highlighted, and error analysis indicated that nonlinear models best explain the adsorption data.