System for the synthesis and characterization of nickel oxide nanoparticles

Abstract

A system for the environmentally friendly synthesis, adsorption testing and characterization of nickel oxide nanoparticles, comprising: a plant extract processing plant configured to extract a phytochemical-rich solution from gooseberry biomass by controlled Soxhlet reflux and continuous water circulation; a pre-reaction and mixing chamber which is operationally connected to the extract preparation unit and is configured to receive metered volumes of the extract and an aqueous nickel nitrate hexahydrate solution, the chamber comprising a temperature-controlled stirrer, a pH probe and a peristaltic feed pump to maintain the homogeneity of the solution and the pH within a predefined range; a microprocessor-controlled calcination and combustion unit connected downstream of the reaction chamber and configured to thermally decompose the reaction mixture into nickel oxide nanoparticles under programmed temperature cycles between 300 °C and 700 °C; a nanoparticle collector and drying system configured to separate, transport and dry the synthesized nanoparticles under inert air circulation at controlled temperature; an adsorption test module with two reaction chambers for simultaneous testing of the adsorption of amaranth dye and hexavalent chromium, each reaction chamber comprising an integrated UV-Vis probe, magnetic stirrer, heating plate and microvalve-controlled reagent inlets for pH modulation; a characterization interface configured to transmit optical and surface data from the nanoparticles via dedicated optical and mechanical coupling ports to analytical instruments such as UV-Vis spectrophotometers, FTIR spectrometers, XRD analyzers, and SEM imaging systems; and a central control and processing unit consisting of a microcontroller configured to receive sensor data from temperature, pH and optical transducers, execute synthesis and adsorption control techniques, calculate adsorption kinetics and output real-time process parameters as well as adsorption efficiency.

Description

Technical field

[0001] The invention relates to the synthesis of nanomaterials and wastewater treatment systems. In particular, it relates to an instrument-based system for the environmentally friendly synthesis and adsorption testing of nickel oxide nanoparticles (NiO-NPs) using a plant extract-based fuel. The system integrates controlled thermal synthesis, automatic pH and temperature control, subsystems for nanoparticle collection and drying, and integrated adsorption and characterization chambers for evaluating the efficiency of heavy metal and dye removal. Background of the invention

[0002] Industrial and textile wastewater often contains organic dyes such as amaranth and toxic heavy metals such as chromium (VI). These pollutants are difficult to biodegrade and pose a significant environmental and health risk even in trace concentrations. Conventional remediation methods such as coagulation, ion exchange, and membrane filtration are expensive, energy-intensive, and generate secondary waste.

[0003] Nickel oxide nanoparticles have proven to be highly effective adsorbents due to their large surface area, active sites, and tunable electronic properties. However, conventional chemical synthesis methods often involve toxic precursors, aggressive reducing agents, and energy-intensive processes.

[0004] The proposed invention overcomes these limitations by introducing an integrated, automated device for the environmentally friendly synthesis and testing of NiO nanoparticles using natural gooseberry extract as a reducing agent and fuel. The device combines various functional modules—extraction, synthesis, calcination, adsorption testing, and characterization—in a single controlled architecture, thus enabling reproducible, energy-efficient, and environmentally sound production and evaluation of nanoparticles.

[0005] The increasing discharge of industrial wastewater containing persistent organic dyes and toxic heavy metals is among the greatest environmental problems of our time. Wastewater from the textile, tanning, electroplating, mining, and metal industries typically contains a complex mixture of organic and inorganic pollutants that are difficult to degrade and accumulate in aquatic ecosystems. Of particular concern are hexavalent chromium [Cr(VI)] and synthetic azo dyes such as amaranth due to their high water solubility, stability to light and heat, and acute toxicity even at trace concentrations. Chromium (VI), widely used in electroplating and leather processing, is known to be carcinogenic and mutagenic, while amaranth, used in textiles, food additives, and cosmetics, exhibits high biochemical resistance to microbial degradation.The persistence of these pollutants in natural waters impairs photosynthesis, reduces oxygen levels, and leads to bioaccumulation. This poses risks to aquatic organisms and human health through contamination of the food chain.

[0006] Existing methods for removing dyes and heavy metals from wastewater can be broadly categorized into physical, chemical, and biological methods. Conventional physical methods include sedimentation, filtration, coagulation-flocculation, membrane separation, and adsorption onto activated carbon or natural zeolites. Chemical processes such as oxidation, electrocoagulation, ion exchange, and precipitation are also frequently used in industrial wastewater treatment. Biological processes such as microbial degradation and phytoremediation offer environmentally friendly alternatives by utilizing bacteria, fungi, and plants that can metabolize or bioaccumulate toxic pollutants. Despite the multitude of available technologies, all these approaches have inherent limitations that prevent efficient, scalable, and sustainable pollutant removal.

[0007] Coagulation and flocculation processes, as well as chemical precipitation methods, require large quantities of coagulation and precipitation agents such as alum, lime, or iron(III) salts. This results in large amounts of secondary sludge that must be further treated and disposed of. The high chemical consumption and constant pH adjustment make these processes economically unviable for large-scale applications. While ion exchangers are effective at removing metal ions, they use expensive resins whose efficiency decreases over time. Furthermore, the regeneration of the ion exchange columns generates secondary saline wastewater streams. Membrane filtration technologies such as ultrafiltration, nanofiltration, and reverse osmosis offer high selectivity but are susceptible to membrane fouling, high operating pressures, and energy-intensive maintenance cycles.Particularly when treating wastewater containing dyes, the membrane pores quickly become clogged due to the high molecular weight and structural stiffness of the dye molecules, leading to a significant reduction in flow rate and service life.

[0008] Advanced oxidation processes (AOPs) such as photocatalysis, ozonation, and Fenton oxidation are frequently investigated for the decomposition of dyes and organic pollutants. These methods rely on the generation of hydroxyl radicals, which can oxidize complex molecules into simpler and less toxic forms. However, their efficiency is often limited by factors such as light penetration depth, reagent stability, and reaction selectivity. For example, photocatalytic decomposition with TiO₂ or ZnO requires UV irradiation and is strongly affected by solution turbidity. Fenton and photo-Fenton processes require precise pH control and the continuous addition of hydrogen peroxide, leading to operational complexities and potential safety hazards.Furthermore, many of these oxidation-based methods are inefficient in the treatment of heavy metals, as they do not oxidize or decompose them, but merely convert them into less toxic oxidation states or adsorb them onto solid surfaces.

[0009] While biological remediation methods are ecologically attractive, they are severely limited by slow reaction kinetics and sensitivity to environmental parameters such as temperature, nutrient concentration, and pH. Many synthetic dyes are resistant to microbial degradation due to their xenobiotic and persistent properties. For example, azo dyes possess -N=N bonds that are difficult to cleave enzymatically, and their degradation products can sometimes be more toxic than the parent compounds. Similarly, the microbial reduction of Cr(VI) to Cr(III) is a slow process requiring the careful maintenance of anaerobic conditions and nutrient sources, which is often incompatible with continuous, large-scale operation. Furthermore, biological systems are susceptible to shock loading and contamination and require long residence times, limiting their industrial applicability.

[0010] Among the various available methods, adsorption has established itself as one of the most effective and versatile techniques for removing dyes and heavy metals from aqueous media. Adsorption offers several key advantages, including high removal efficiency, ease of handling, flexible design options, and insensitivity to toxic contaminants. Activated carbon, due to its extremely large surface area and porous structure, has traditionally been the most widely used adsorbent. However, the regeneration of activated carbon is expensive, and its adsorption capacity decreases after several cycles due to pore clogging and surface oxidation. Furthermore, the regeneration process, which typically involves high-temperature heat treatment, leads to partial degradation of the carbon structure and the emission of greenhouse gases, making the process less sustainable.

[0011] To address the costs and regeneration effort of activated carbon, researchers have investigated numerous alternative adsorbents such as clays, zeolites, silica gel, agricultural waste, and biosorbents derived from plant and microbial materials. Although these materials are inexpensive and readily available, their adsorption capacity is generally limited by small surface area, insufficient active binding sites, and poor mechanical stability. Modification through acid, base, or surfactant treatment can improve performance but again necessitates the use of chemicals and thus environmental pollution. Furthermore, natural adsorbents often exhibit selectivity for specific ions or dye molecules, requiring complex pretreatment steps or multi-stage processes for complete remediation.

[0012] Nanotechnology has revolutionized wastewater treatment by providing materials with exceptionally high surface-to-volume ratios, tunable surface chemistry, and reactive centers. Metal oxide nanoparticles such as titanium dioxide, zinc oxide, iron oxide, and nickel oxide have been extensively studied as advanced adsorbents and photocatalysts. In particular, nickel oxide (NiO) nanoparticles exhibit excellent chemical stability, high electrostatic adsorption capacity, and variable oxidation states, making them ideally suited for the removal of cationic and anionic pollutants. The ability of NiO nanoparticles to interact with dyes and heavy metals via surface complexation and electrostatic attraction enables their efficient removal even at low concentrations.However, the synthesis of NiO₂ nanoparticles traditionally relies on chemical processes such as sol-gel, precipitation, or hydrothermal methods, which use toxic solvents, reducing agents, and surfactants. These processes generate hazardous byproducts, require precise temperature control, and consume large amounts of energy.

[0013] Chemical reduction processes often utilize hydrazine, sodium borohydride, or ethylene glycol as reducing agents. These reagents are not only expensive but also highly toxic and unstable, posing environmental and safety risks. Similarly, surfactants and stabilizers used to control nanoparticle morphology can remain adsorbed onto particle surfaces, reducing the number of active sites available for adsorption. Furthermore, the disposal of chemical residues after synthesis leads to additional contamination. The lack of a sustainable and environmentally friendly synthesis pathway for metal oxide nanoparticles remains a significant obstacle to their practical application in wastewater treatment.

[0014] In recent years, green synthesis methods using plant extracts, microorganisms, and biopolymers have gained importance as sustainable alternatives to conventional nanoparticle synthesis. Plant-mediated synthesis utilizes the reducing, stabilizing, and chelating properties of phytochemicals such as polyphenols, flavonoids, alkaloids, and terpenoids. These compounds act simultaneously as reducing and stabilizing agents, thus eliminating the need for toxic chemicals. Despite these advantages, most described green synthesis methods are performed manually using laboratory equipment without standardization or process control, resulting in low reproducibility and variable particle properties.Parameters such as precursor concentration, extract volume, temperature, and reaction time are often optimized empirically, and even small deviations can result in significant changes in particle size, morphology, and surface charge. The lack of automated control systems limits the scalability of green synthesis for industrial or pilot plants.

[0015] Another limitation of existing studies is that synthesis and adsorption testing are typically performed as separate, non-integrated processes. Nanoparticles synthesized using bioextracts are manually collected, dried, and then tested for adsorption in independent batches. This disjointed workflow increases the risk of contamination, leads to inconsistencies in material handling, and prevents real-time correlation between synthesis conditions and adsorption performance. Furthermore, characterization techniques such as UV-Vis spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) are typically performed offline, after synthesis is complete, which increases analysis time and reduces the efficiency of process feedback.

[0016] There is therefore an urgent need for an integrated, automated system that enables the controlled, environmentally friendly synthesis of metal oxide nanoparticles, continuously monitors reaction parameters such as temperature, pH, and concentration, and directly evaluates adsorption performance against pollutants within the same structural platform. Such a system should minimize human intervention, standardize synthesis conditions, and enable reproducible nanoparticle production, while simultaneously allowing for real-time characterization and kinetic modeling of adsorption behavior. The development of a unified machine structure that combines thermal synthesis, extract preparation, calcination, nanoparticle harvesting, and adsorption testing in a single automated framework would represent a significant technological advancement over existing, fragmented laboratory methods.

[0017] The proposed integrated system for the environmentally friendly synthesis and adsorption testing of nickel oxide nanoparticles using gooseberry extract aims to close this technological gap. By replacing toxic reducing agents with natural bioactive compounds from plant extracts and integrating process control sensors to monitor temperature, pH, and concentration, the system ensures both environmental safety and high synthesis precision. Furthermore, the integrated adsorption testing module eliminates the need for external batch approaches and enables in-situ evaluation of adsorption capacity and kinetic parameters. This technological convergence not only improves reproducibility but also provides a sustainable, efficient, and scalable route to the production of functional nanomaterials specifically designed for wastewater treatment.In contrast to existing manual and chemical-intensive methods, the proposed system achieves automation, environmental friendliness and process integration, thus addressing the key limitations of current solutions in the field of nanoparticle-based environmental remediation. Summary of the invention

[0018] The invention relates to a compact machine system comprising: a raw material loading and extraction chamber for the production of gooseberry extract; a precursor mixing and dissolution reaction chamber for the formation of nickel nitrate extract mixtures; a controlled heating and calcination device for nanoparticle synthesis; a nanoparticle collection and drying subsystem; and an integrated adsorption and characterization unit for automated testing of the adsorption efficiency of amaranth dye and Cr(VI).

[0019] The system includes digital sensors for real-time monitoring of temperature, pH, and concentration, a programmable microcontroller for process control, and data acquisition interfaces for UV-Vis, FTIR, SEM, and XRD analysis modules. This enables high reproducibility and precision in both synthesis and the evaluation of adsorption efficiency.

[0020] The present invention aims to provide an integrated and automated system for the environmentally friendly synthesis, adsorption testing, and characterization of nickel oxide (NiO) nanoparticles. A natural plant extract, for example from gooseberries, serves as the reduction and fuel medium. The invention overcomes the disadvantages of conventional chemical synthesis methods, which rely on toxic reagents, energy-intensive processes, and non-reproducible manual procedures. By introducing a self-contained and automated hardware structure, the invention enables a controlled, environmentally friendly, and reproducible synthesis process for NiO nanoparticles, which can then be directly subjected to adsorption tests within the same system.

[0021] A further objective of the invention is to provide a system that, through integrated sensors and a microcontroller-based feedback mechanism, ensures precise control of key synthesis parameters such as temperature, pH, concentration, and reaction time. This enables the precise optimization of reaction kinetics and nanoparticle properties, ensuring a uniform size distribution, morphology, and crystallinity. Through automated calibration and process monitoring, the system reduces human error and variations, resulting in consistent and reproducible nanoparticle batches with predictable adsorption behavior towards heavy metals and dyes.

[0022] A further objective of the invention is to provide a device for performing complete adsorption tests of toxic pollutants such as amaranth and hexavalent chromium (Cr(VI)) under programmable conditions. The system features a dual adsorption chamber, enabling the simultaneous investigation of multiple pollutants in variable pH, temperature, and concentration ranges. Integrated optical sensors and UV / Vis spectrophotometers allow for real-time monitoring of absorption and pollutant concentration, and thus the direct calculation of adsorption efficiency, capacity, and equilibrium constants using integrated computational methods. This integration ensures the dynamic modeling of the kinetics—both pseudo-first and pseudo-second order—without external instruments or manual sampling.

[0023] A further objective of the invention is to provide an environmentally friendly process for nanoparticle synthesis that completely eliminates the use of hazardous chemicals such as hydrazine, sodium borohydride, or ethanol-based reducing agents. The use of gooseberry extract as a natural source of polyphenols, flavonoids, and organic acids not only promotes the reduction and stabilization of nickel ions but also improves the biocompatibility and surface reactivity of the resulting NiO nanoparticles. This environmentally friendly approach reduces pollutant emissions, chemical waste, and overall energy consumption, thus ensuring compliance with global environmental and safety regulations.

[0024] A further objective of the invention is the development of a modular system architecture that integrates synthesis, calcination, drying, and adsorption testing into a single, continuous workflow. The device structure is designed to enable automated material transfer between the plant extract preparation chamber, the precursor mixing reactor, the calcination furnace, the nanoparticle collector, and the adsorption module. Pneumatic arms and vacuum transfer lines minimize material losses and cross-contamination. This integration not only reduces processing time but also enables a closed-loop control system in which synthesis results are directly correlated with adsorption performance parameters. This establishes direct cause-and-effect relationships between production parameters and functional efficiency.

[0025] A further objective of the invention is to provide a device with integrated characterization interfaces for the spectroscopic and microscopic analysis of synthesized NiO nanoparticles. The system includes optical and mechanical couplings that enable direct connection to instruments such as FTIR, UV-Vis, XRD, and SEM without removing the samples from the closed synthesis environment. This facilitates in-situ characterization and reduces analysis time, while simultaneously ensuring that the nanoparticles are not exposed to environmental contaminants or moisture before evaluation. The characterization data thus obtained are automatically stored and processed in the system's microcontroller unit for later retrieval and analysis.

[0026] A further objective of the invention is to provide a versatile and adaptable platform that can be used not only for NiO nanoparticles but also for other metal oxide nanomaterials such as ZnO, CuO, and Fe₂O₃ by replacing the corresponding metal nitrate precursors and maintaining similar operating conditions. This adaptability enables the system to serve as a universal platform for the environmentally friendly synthesis of various nanomaterials that find application in water treatment, catalysis, or energy technology.

[0027] Another important objective of the invention is to provide a self-calibrating and energy-efficient thermal management system that minimizes energy consumption during the calcination and drying processes. The device utilizes intelligent heating techniques and temperature sensors to ensure uniform heating profiles, thereby improving the crystallinity and purity of the synthesized nanoparticles. By employing programmable calcination cycles, the system achieves phase-pure NiO nanoparticles with an increased surface area and enhanced adsorption potential, while simultaneously reducing operating costs.

[0028] A further objective of the invention is the real-time modeling of adsorption phenomena with respect to kinetics and thermodynamics using integrated computational methods. The system's control unit is designed to execute mathematical models according to the Langmuir and Freundlich isotherms and to calculate parameters such as adsorption capacity, rate constants, and equilibrium constants directly from the real-time concentration data. This enables users and researchers to immediately evaluate the adsorption efficiency and predict performance under various environmental conditions without having to resort to subsequent data processing.

[0029] A further objective of the invention is the simple regeneration and reuse of the synthesized NiO nanoparticles. The system comprises a module for controlled purification and reactivation, which rinses the used nanoparticles with mild acid or base solutions, dries them, and reuses them for new adsorption cycles. This ensures high material efficiency and contributes to long-term sustainability, as the need for continuous synthesis of new batches is reduced.

[0030] A further objective of the invention is the development of a compact, safe, and user-friendly laboratory device that can be scaled for pilot or industrial applications. Safety interlocks, overheating protection, pressure relief valves, and sealed reaction chambers ensure safe operation even during synthesis steps at high temperatures and pressures. Thanks to its compact design, the system fits into standard laboratories while offering the robustness and automation required for industrial applications.

[0031] The invention ultimately aims to create a technological advancement that bridges the gap between the principles of green chemistry and industrial automation. The integrated NiO-NanoSynth system combines environmentally friendly synthesis methods with advanced process control, thus offering a unified solution for the production, evaluation, and optimization of nanoparticles. Compared to conventional manual or chemical-intensive methods, it achieves significant improvements in reproducibility, efficiency, and environmental compatibility. By combining precision engineering, digital control, and green synthetic chemistry on a single structural platform, the invention fulfills the long-standing need for a sustainable, intelligent, and integrated machine system for nanomaterial synthesis and wastewater treatment. BRIEF DESCRIPTION OF THE IMAGE

[0032] These and other features, aspects and advantages of the present invention will be better understood if the following detailed description is read with reference to the accompanying drawing, in which the same symbols represent the same parts: Fig. Figure 1 shows a block diagram of an integrated system for the environmentally friendly synthesis, adsorption and characterization of nickel oxide nanoparticles.

[0033] Furthermore, those skilled in the art will recognize that the elements in the drawing are simplified and not necessarily drawn to scale. For example, the flowcharts illustrate the process by highlighting the main steps to facilitate understanding of the present disclosure. With regard to the construction of the device, one or more components may be represented in the drawing by conventional symbols. The drawing may show only the specific details relevant to understanding the embodiments of the present disclosure, so as not to clutter the drawing with details that are already apparent to those skilled in the art from the description contained herein. Detailed description of the invention

[0034] To facilitate understanding of the principles of the invention, reference is made below to the embodiment shown in the drawing, which is described using specific terms. It is understood, however, that this does not limit the scope of protection of the invention. Rather, modifications and further developments of the depicted system, as well as further applications of the inventive principles shown therein, are conceivable, insofar as they would normally occur to a person skilled in the art in the field of the invention.

[0035] It will be clear to those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not to be understood as a limitation thereof.

[0036] References to “an aspect”, “another aspect”, or similar phrases in this description mean that a particular feature, structure, or property described in connection with the embodiment is included in at least one embodiment of the present disclosure. Therefore, phrases such as “in one embodiment”, “in another embodiment”, and similar expressions in this description may, but do not necessarily, all refer to the same embodiment.

[0037] The terms "includes," "comprehensive," or similar expressions denote non-exclusive inclusion. Thus, a procedure or method containing a list of steps does not only include those steps but may also include further steps not explicitly listed or inherent in the procedure or method. Likewise, the statement "includes..." for one or more devices, subsystems, elements, structures, or components, without further limitations, does not preclude the existence of other devices, subsystems, elements, structures, or components.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meanings generally known to those skilled in the art in the field to which this invention belongs. The systems, methods, and examples described herein serve only for illustration and are not to be understood as limiting.

[0039] Embodiments of the present disclosure are described in detail below with reference to the attached drawing.

[0040] In Fig.Figure 1 shows a block diagram of an integrated system for the environmentally friendly synthesis, adsorption, and characterization of nickel oxide nanoparticles. The system 100 comprises: a plant extract preparation unit (102) for extracting a phytochemical-rich solution from gooseberry biomass by controlled Soxhlet reflux and continuous water circulation; a precursor reaction and mixing chamber (104) operationally connected to the extract preparation unit, which receives metered volumes of the extract and an aqueous nickel nitrate hexahydrate solution, the chamber including a temperature-controlled stirrer, a pH probe, and a peristaltic pump to maintain solution homogeneity and pH within a predefined range;a microprocessor-controlled calcination and combustion unit (106) connected downstream of the reaction chamber, enabling the thermal decomposition of the reaction mixture into nickel oxide nanoparticles under programmed temperature cycles between 300 °C and 700 °C; a nanoparticle collection and drying system (108) for separating, transporting, and drying the synthesized nanoparticles under inert gas circulation at a controlled temperature; an adsorption test module (110) with two reaction chambers for simultaneously testing the adsorption of amaranth dye and hexavalent chromium, each reaction chamber comprising an integrated UV-Vis probe, a magnetic stirrer, a hot plate, and microvalve-controlled reagent inlets for pH modulation;a characterization interface (112) for transmitting optical and surface data of the nanoparticles to analytical instruments such as UV-Vis spectrophotometers, FTIR spectrometers, XRD analyzers and SEM imaging systems via dedicated optical and mechanical coupling ports; and a central control and processing unit (114) with a programmable microcontroller that receives sensor data from temperature, pH and optical transducers, performs synthesis and adsorption control techniques, calculates the adsorption kinetics and outputs real-time process parameters and the adsorption efficiency.

[0041] In one embodiment, the plant extract preparation unit (102) comprises a cylindrical Soxhlet reactor with a double-walled glass column, a heating jacket integrated with a proportional integral differential controller (PID), and a reflux condenser coupled to a vacuum-assisted filtration unit. The system is configured to operate at a stable temperature of 65 °C ± 2 °C to extract phenolic, flavonoid, and carboxylic acid compounds responsible for the reduction and stabilization of nickel ions during nanoparticle formation.

[0042] In one embodiment, the precursor reaction and mixing chamber (104) comprises: a borosilicate vessel with an internal PTFE-coated surface to prevent precursor adsorption; a magnetic stirrer configured to ensure uniform mixing of the solution at 500-800 rpm; a pH electrode coupled with an automatic acid-base titration controller to regulate the pH of the reaction mixture between 6.0 and 8.0; and at least one embedded thermocouple connected to the control unit to maintain the reaction temperature between 60°C and 70°C, thus ensuring controlled nucleation and controlled growth of the nickel hydroxide intermediates prior to calcination.

[0043] In one embodiment, the calcination and combustion arrangement (106) comprises a muffle furnace with an integrated programmable logic controller (PLC) and multiple resistance heating coils. The arrangement is configured to follow a multi-stage temperature profile that includes a preheating ramp, a sustained oxidation phase, and a cooling cycle. The total heating time is 4 to 6 hours. This produces highly crystalline nickel oxide nanoparticles with an average crystallite size between 12 nm and 20 nm.

[0044] In one embodiment, the nanoparticle collection and drying system (108) comprises an infrared-assisted drying chamber with recirculating airflow, a cyclone separator for powder recovery, and a pneumatic actuator configured to automatically transfer the dried NiO nanoparticles into sealed antistatic containers without manual handling, thereby minimizing contamination and exposure to atmospheric humidity.

[0045] In one embodiment, the adsorption test module (110) comprises two independent reaction vessels mounted on precision stir plates, each vessel having the following: a quartz cuvette window aligned with a UV-visible photodiode array for continuous optical monitoring of the dye or metal ion concentration; Microvalve-controlled dosing inlets for adding hydrochloric acid or sodium hydroxide to maintain the pH of the solution in the range of 2 to 12; a microheating element that maintains a constant adsorption temperature of 25°C ± 0.5°C; and a peristaltic circulation loop that ensures a homogeneous suspension of the NiO nanoparticles during the adsorption process.

[0046] In one embodiment, the characterization interface (112) further comprises an optically fiber-coupled transmission channel and a detachable vacuum feedthrough for seamless transfer of the synthesized samples to the characterization instruments. This enables in-situ analysis of the optical band gap, functional group vibrations, and crystal structure without having to remove the samples from the closed synthesis environment.

[0047] In one embodiment, the control and processing unit (114) comprises: an ARM Cortex-based microcontroller equipped with an embedded data acquisition card for the simultaneous processing of multi-sensor input data; Firmware stored in non-volatile memory that includes control techniques for temperature regulation, pH stabilization, and process sequencing; and Computing modules for running adsorption kinetics and isotherm models, including pseudo-first-order, pseudo-second-order, Langmuir and Freundlich models, and for generating real-time outputs of adsorption efficiency based on continuous UV-Vis absorption data.

[0048] In one embodiment, the system includes a closed-loop control system in which the microcontroller dynamically adjusts the thermal input, reagent dosage, and reaction time based on real-time sensor data deviations, with a control latency of less than 200 milliseconds. This ensures consistent synthesis and prevents temperature or pH overshoot.

[0049] The present invention relates to an integrated and automated system for the environmentally friendly synthesis, adsorption testing, and characterization of nickel oxide (NiO) nanoparticles. The system is a closed, modular structure with multiple process units, each electronically controlled and functionally interconnected to enable continuous, reproducible, and environmentally friendly nanoparticle production and testing. The structural components correspond to the elements defined in the claims and each contributes significantly to the precision, repeatability, and real-time monitoring of the synthesis and adsorption phases.

[0050] The core of the system is the plant extraction unit, which uses Soxhlet extraction to extract a phytochemical-rich gooseberry solution. The extract serves as both a reducing and stabilizing medium for nickel nitrate precursors. The extraction process begins with heating distilled water and ground gooseberry pulp in a temperature-controlled jacket within a closed reflux chamber at 65 °C ± 2 °C. Continuous peristaltic recirculation ensures a uniform solvent flow through the biomass bed. Phenolic, flavonoid, and carboxylic acid compounds are released into the aqueous phase, forming an extract with high reduction potential. Vacuum filtration using Whatman No. 1 filter paper completely removes pulp residue and particles, and the clear, yellowish-brown extract is conveyed via a sealed line to the reaction and mixing chamber for the precursors.

[0051] The reaction chamber consists of a chemically inert borosilicate glass vessel with a PTFE inner coating to prevent nickel adsorption to the walls. It is equipped with a mechanical stirrer, a digital thermocouple, a pH electrode, and automatic dosing connections linked to reservoirs containing gooseberry extract and nickel nitrate hexahydrate solution with controlled molarity. The control and processing unit regulates the flow rates of both components and maintains stoichiometric ratios in the range of 1:2 to 1:4 (extract to precursor). The integrated pH control system continuously monitors the acidity of the solution and injects dilute acid or base via microvalves to ensure a stable pH between 6 and 8. This controlled pH environment prevents premature precipitation of nickel hydroxide while simultaneously promoting the nucleation of uniform precursor complexes.The microcontroller's firmware continuously analyzes temperature and pH feedback using a PID (Proportional-Integral-Differential) controller to dynamically adjust heating power and dosing rate.

[0052] After precursor formation is complete, the reaction mixture is transferred to the calcination and combustion unit. This subsystem comprises a high-temperature furnace with an integrated programmable logic controller (PLC) and multiple resistance heating coils distributed along the ceramic chamber walls. The control unit initiates a programmed temperature profile with a gradual heating from room temperature to 300 °C, followed by three hours of oxidation at 500 °C and a final two-hour crystallization at 700 °C. During this process, the system automatically regulates the airflow through an oxygen inlet valve to ensure stoichiometric oxidation of the nickel precursor and thus the formation of high-purity NiO nanoparticles. The firmware performs dynamic temperature stabilization using real-time thermocouple data to maintain temperature fluctuations within ±1 °C.The PID controller adjusts the power consumption according to the difference between the target and actual temperature, thus ensuring precise energy supply and uniform calcination.

[0053] After calcination, the product is automatically conveyed via a pneumatic conveying channel into the nanoparticle collector and drying system. The collector consists of a cyclone separator connected to an IR-assisted drying chamber. The chamber maintains a constant temperature of 80 °C and ensures uniform moisture removal through a controlled airflow. Integrated sensors monitor humidity and air pressure and provide real-time data to the central control unit, which regulates the airflow and the intensity of the IR lamp. Once drying is complete, the nanoparticles are pneumatically transferred under inert conditions into sealed containers to minimize contamination and agglomeration.

[0054] The adsorption test module is directly connected to the nanoparticle collector, allowing freshly synthesized NiO₂ nanoparticles to be automatically dosed into the test chambers without contact with ambient humidity. Each chamber of the dual adsorption module is designed for simultaneous and independent experiments with amaranth dye and hexavalent chromium (Cr(VI)). Both chambers are equipped with UV-Vis photodiode arrays arranged along the quartz cuvette windows, enabling continuous optical absorption measurements. The chambers also contain microheaters and stirrers to ensure uniform temperature distribution and a homogeneous nanoparticle suspension. The microcontroller regulates the pH using automated titration microvalves connected to acid and base reservoirs, allowing dynamic control between pH 2 and 12.

[0055] The adsorption method is designed to perform kinetic modeling in parallel with data acquisition. Two models—pseudo-first-order and pseudo-second-order kinetics—are continuously fitted to the data stream using the least-squares method. The method dynamically updates the rate constants (k1) and (k2) as well as the equilibrium adsorption capacity (q). e ), as soon as new data points are received. This allows the system to identify the model that best describes the adsorption behavior for each pollutant. Once an equilibrium is reached (recognizable by a negligible change in concentration over several measurements), the system automatically starts data logging, storage, and calculation of thermodynamic parameters such as the Gibbs free energy (ΔG), enthalpy (ΔH), and entropy (ΔS).

[0056] A key aspect of the technical control system is the integration of a closed-loop control system. The microcontroller monitors all relevant parameters—temperature, pH, absorbance, and reaction time—and continuously compares them to preset threshold values. If a deviation from the permissible limits is detected, the firmware immediately implements corrective actions, such as adjusting the heating power, modifying the acid or base flow rates, or extending the adsorption time. The control system's response time is less than 200 milliseconds, thus ensuring real-time process stability and precision.

[0057] The system's characterization interface serves as an automated data bridge between the synthesis unit and analytical instruments such as FTIR, XRD, and SEM. Via fiber optic and vacuum feedthrough channels, the system enables the direct transfer of synthesized samples for in-situ analysis. The microcontroller initiates spectroscopic scans and acquires characteristic peaks—such as Ni-O vibrational modes in FTIR spectroscopy and diffraction planes (111), (200), and (220) in XRD spectroscopy. The firmware processes the acquired spectral data to determine the optical band gap using the Tauc equation, while the SEM interface transmits high-resolution morphological data for surface characterization.

[0058] The overall process control is managed by the firmware's main execution sequence, which is divided into six functional phases: extract preparation, precursor reaction, calcination, cooling, adsorption, and analysis. Each phase is controlled by specific technical modules with predefined sensor conditions and logical transitions. The process is based on a finite automaton model, in which the completion of one state (e.g., reaching a stable pH in the reaction chamber) triggers the automatic transition to the next state (e.g., transition to the calcination phase). The internal system clock and event scheduler coordinate these transitions, while data integrity is ensured through continuous checksum verification of the sensor inputs.

[0059] A computing subsystem integrated into the control unit performs adsorption isotherm analyses using real-time data. The method automatically fits the acquired equilibrium data to Langmuir and Freundlich isotherm models using linear regression and determines the respective constants (K_L), (q_{max}) and (K_F), (1 / n). The control software evaluates the regression correlation coefficients (R). 2 The system performs calculations to determine which model better describes the adsorption phenomenon. This provides real-time insights into the surface heterogeneity and adsorption behavior of monolayers. These calculations are performed in the microcontroller and displayed on the user interface along with dynamic graphs of concentration over time, adsorption capacity over time, and isothermal relationships.

[0060] The device is also capable of performing regeneration cycles of the NiO₂ nanoparticles used. The regeneration process begins with an automated rinsing procedure using controlled acid and base solutions, followed by drying under the same infrared-assisted system. The regenerated nanoparticles are then automatically returned to the adsorption chamber for the next test cycle. The efficiency of each regeneration cycle is monitored by comparing the new adsorption capacity with that of the first cycle. This allows the system to calculate the deterioration of adsorption performance with repeated reuse.

[0061] All data acquired during synthesis, adsorption, and characterization are continuously logged with timestamps in the system's internal memory. Prior to analysis, the process performs automatic data normalization, outlier detection, and signal smoothing using moving average filters. A graphical user interface allows users to visualize real-time graphs, select operational sequences, and export data via USB or wireless interface.

[0062] Through the integrated combination of intelligent control technologies, automated hardware synchronization, and real-time analysis calculations, the invention enables highly reproducible, environmentally friendly, and efficient synthesis and evaluation of NiO nanoparticles. The closed-loop control system ensures minimal human intervention, precise process stability, and on-site validation of material properties. By combining synthesis, testing, and analysis in a single digital control system, the system makes a significant contribution to nanoparticle production and environmental remediation, setting a technological benchmark for automated, environmentally friendly nanomaterial production systems.

[0063] The invention relates to nanotechnology and environmental engineering, in particular systems and devices for the synthesis, testing, and characterization of nanomaterials for pollutant adsorption and water purification. More specifically, it is a hardware-integrated, technology-oriented system for the environmentally friendly synthesis of nickel oxide nanoparticles using plant bioextracts as reducing and stabilizing agents. The system also includes automated mechanisms for testing the adsorption of dyes and heavy metal ions in aqueous solutions and enables the real-time analysis of kinetic and isothermal adsorption models. The invention combines principles of chemical engineering, materials science, control engineering, and analytical instrumentation in a single automated platform for the closed-loop production and evaluation of nanomaterials.It overcomes the limitations of conventional nanoparticle synthesis methods based on hazardous chemicals and manual batch processes, introducing a sustainable, reproducible, and intelligent system that enables dynamic parameter control, in-situ data acquisition, and computer-aided evaluation of adsorption efficiency. The application area encompasses the research and industrial-scale synthesis of metal oxide nanomaterials for wastewater treatment, environmental monitoring, catalysis, and surface functionalization, where precision control and environmentally friendly processing are crucial requirements.

[0064] The drawing and the preceding description illustrate embodiments. Those skilled in the art will recognize that one or more of the described elements can be combined to form a single functional element. Alternatively, certain elements can be divided into several functional elements. Elements of one embodiment can be added to another. For example, the process flows described here can be modified and are not limited to the manner described herein. Furthermore, the actions of a flowchart need not be performed in the sequence shown; nor do all actions necessarily need to be carried out. Actions that do not depend on other actions can be performed in parallel with the other actions. The scope of protection of the embodiments is in no way limited by these specific examples. Numerous variations, whether explicitly stated in the description or not, such as...Differences in structure, dimensions, and materials are possible. The scope of protection of the embodiments is at least as comprehensive as described by the following claims.

[0065] The advantages, other benefits, and problem solutions have been described above with reference to specific embodiments. However, the advantages, benefits, problem solutions, and any components that can effect or enhance an advantage, benefit, or solution are not to be construed as critical, necessary, or essential features or components of the claims. REFERENCES 100 An Integrated System For The Environmentally Friendly Synthesis, Adsorption And Characterization Of Nickel Oxide Nanoparticles. 102 Plant extract processing unit 104 Precursor Reaction and Mixing Chamber 106 Microprocessor-controlled calcination and combustion plant 108 Nanoparticle Collector and Drying System 110 Adsorption test module 112 Characterization interface 114 Central Control and Processing Unit

Claims

[1] A system for the environmentally friendly synthesis, adsorption testing and characterization of nickel oxide nanoparticles, comprising: a plant extract processing plant configured to extract a phytochemical-rich solution from gooseberry biomass by controlled Soxhlet reflux and continuous water circulation; a pre-reaction and mixing chamber which is operationally connected to the extract preparation unit and is configured to receive metered volumes of the extract and an aqueous nickel nitrate hexahydrate solution, the chamber comprising a temperature-controlled stirrer, a pH probe and a peristaltic feed pump to maintain the homogeneity of the solution and the pH within a predefined range; a microprocessor-controlled calcination and combustion unit connected downstream of the reaction chamber and configured to thermally decompose the reaction mixture into nickel oxide nanoparticles under programmed temperature cycles between 300 °C and 700 °C; a nanoparticle collector and drying system configured to separate, transport and dry the synthesized nanoparticles under inert air circulation at controlled temperature; an adsorption test module with two reaction chambers for simultaneous testing of the adsorption of amaranth dye and hexavalent chromium, each reaction chamber comprising an integrated UV-Vis probe, magnetic stirrer, heating plate and microvalve-controlled reagent inlets for pH modulation; a characterization interface configured to transmit optical and surface data from the nanoparticles via dedicated optical and mechanical coupling ports to analytical instruments such as UV-Vis spectrophotometers, FTIR spectrometers, XRD analyzers, and SEM imaging systems; and a central control and processing unit consisting of a microcontroller configured to receive sensor data from temperature, pH and optical transducers, execute synthesis and adsorption control techniques, calculate adsorption kinetics and output real-time process parameters as well as adsorption efficiency. [2] System according to claim 1, wherein the plant extract preparation unit comprises a cylindrical Soxhlet reactor with a double-walled glass column, a heating jacket integrated with a proportional integral differential controller (PID), and a reflux condenser coupled with a vacuum-assisted filtration unit, wherein the system is configured to operate at a stable temperature of 65 °C ± 2 °C to extract phenolic, flavonoid, and carboxylic acid compounds responsible for the reduction and stabilization of nickel ions during nanoparticle formation. [3] System according to claim 1, wherein the precursor reaction and mixing chamber comprises: a borosilicate vessel with an internal PTFE-coated surface to prevent precursor adsorption; a magnetic stirrer configured to ensure uniform mixing of the solution at 500-800 rpm; a pH electrode coupled to an automatic acid-base titration controller to regulate the pH of the reaction mixture between 6.0 and 8.0; and at least one embedded thermocouple connected to the control unit to maintain the reaction temperature between 60°C and 70°C, thus ensuring controlled nucleation and controlled growth of the nickel hydroxide intermediates prior to calcination. [4] System according to claim 1, wherein the calcination and combustion arrangement comprises a muffle furnace with integrated programmable logic controller (PLC) and multiple resistance heating coils, wherein the arrangement is configured to follow a multi-stage temperature profile comprising a preheating ramp, a sustained oxidation phase and a cooling cycle, wherein the total heating time is between 4 and 6 hours, producing highly crystalline nickel oxide nanoparticles with an average crystallite size between 12 nm and 20 nm. [5] System according to claim 1, wherein the nanoparticle collection and drying system comprises an infrared-assisted drying chamber with recirculating airflow, a cyclone separator for powder recovery and a pneumatic actuator configured to automatically transfer the dried NiO nanoparticles into sealed antistatic containers without manual handling, thereby minimizing contamination and exposure to atmospheric humidity. [6] System according to claim 1, wherein the adsorption test module comprises two independent reaction vessels mounted on precision stir plates, each vessel having the following: a quartz cuvette window aligned with a UV-visible photodiode array for continuous optical monitoring of the dye or metal ion concentration; Microvalve-controlled dosing inlets for adding hydrochloric acid or sodium hydroxide to maintain the pH of the solution in the range of 2 to 12; a micro heating element that maintains a constant adsorption temperature of 25°C ± 0.5°C; and a peristaltic circulation loop that ensures a homogeneous suspension of the NiO nanoparticles during the adsorption process. [7] System according to claim 1, wherein the characterization interface further comprises an optically fiber-coupled transmission channel and a removable vacuum feedthrough for seamless transfer of the synthesized samples to the characterization instruments, thereby enabling in-situ analysis of the optical band gap, the vibrations of functional groups and the crystal structure without removing the samples from the closed synthesis environment. [8] System according to claim 1, wherein the control and processing unit comprises: an ARM Cortex-based microcontroller equipped with an embedded data acquisition card for the simultaneous processing of multi-sensor input data; Firmware stored in non-volatile memory that includes control techniques for temperature regulation, pH stabilization, and process sequencing; and Computing modules for running adsorption kinetics and isotherm models, including pseudo-first-order, pseudo-second-order, Langmuir and Freundlich models, and for generating real-time outputs of adsorption efficiency based on continuous UV-Vis absorption data. [9] System according to claim 1, wherein the system comprises a closed feedback mechanism in which the microcontroller dynamically adjusts the thermal input, reagent dosage and reaction time based on real-time sensor data deviations, wherein the latency of the control response is less than 200 milliseconds, thereby maintaining the uniformity of the synthesis and avoiding overshoot of the temperature or pH value.

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