Sustainable-controlled release fertilizer and synthesis method thereof

Abstract

A sustainable control release fertilizer and a producing method thereof are developed. The sustainable control release fertilizer comprises a natural char / struvite composite with different ratio of the natural char to struvite (0:100, 25:75, 50:50, 75:25). The natural char / struvite composites represent a phosphorus pentoxid content in a range of 16 wt% to 25 wt% which is more than a common phosphate fertilizer. Furthermore, a mole ratio of Mg2+:NH4+:PO4 3- in the sustainable control release fertilizer is 2:1:1. The sustainable control release fertilizer can enhance phosphorus uptake of at least one plant at early stage of growth due to its composition as well as the developed producing method of sustainable control release fertilizer is based on recovery of phosphorus from wastewater that has the good economic and environmental effects.

Description

SUSTAINABLE-CONTROLLED RELEASE FERTILIZER AND SYNTHESISMETHOD THEREOFTECHNICAL FIELD

[0001] The present disclosure is generally related to an exemplary sustainable / controlled release fertilizer and an exemplary method for synthesizing sustainable / controlled release fertilizer, and more particularly to an exemplary natural char / struvite composite and an exemplary method for synthesizing exemplary natural char / struvite composite with a phosphorus pentoxid (P2O5) content in a range of 16 %wt to 25 %wt.BACKGROUND

[0002] Phosphorus is one of the most consumed and irreplaceable essential elements in agricultural industries due to its functional properties involved in biochemical processes, plant growth, and development of reproductive organs. These days, the agricultural production in the world is highly depends on utilizing phosphorus -based fertilizer to provide a required amount of the phosphorus for the plants. Due to the low efficiency and polluting the water and environment by using the conventional phosphate fertilizers such as superphosphate and ammonium phosphate, especially in calcareous soils, the limited phosphate rock reserves as well as the expansion of the enrichment phenomenon of coastal waters, a phosphorus recycling from renewable sources of phosphorus in a form of fertilizer has been considered.

[0003] In order to improve an efficiency of phosphorus consumption and plant growth and reduce environmental hazards, developing a fertilizer with a controlled release of phosphorus has attracted the attention of the agricultural industries as well as researchers. These types of fertilizer are known as a sustainable-control release fertilizer that are developed in many different ways.

[0004] One of the developed sustainable-control release fertilizer is struvite (magnesium ammonium phosphate) with a chemical formula of NlLMgPO / .- 6H2O which is produced using the wastewater or sewage as the renewable resources of phosphorus. The struvite can gradually provide phosphorus to the plant and reduce the stability and leaching of phosphorus in the soil. However, due to the very low solubility of struvite, the plant's access to phosphorus will be difficult in the early stages of growth. Therefore, there is a need to develop a cost-effective struvite-based fertilizer that can provide the phosphorus in need of plant in the early stage of its growth in a continuous and control state.

[0005] On the other hand, the natural char, as a type of stable organic material and resistant to microbial decomposition, may help the plant in increasing the availability of native and low- soluble soil nutrients including phosphorus and thereby reduce the pollution caused by the use of soluble phosphate fertilizers.

[0006] Thus, herein a cost effective sustained-control release fertilizer comprising a natural char / struvite composite and a synthesis method thereof from a wastewater is developed. The developed natural char / struvite composite has a phosphorus pentoxid content more than 16 %wt.SUMMARY

[0007] This summary is intended to provide an overview of the subject matter of the present disclosure, and is not intended to identify essential elements or key elements of the subject matter, nor is it intended to be used to determine the scope of the claimed implementations. Its sole purpose is to present some concepts of one or more exemplary aspects in a simplified form as a prelude to the more detailed description that is presented later. The proper scope of the present disclosure may be ascertained from the claims set forth below in view of the detailed description below and the drawings.

[0008] One or more exemplary embodiments describe an exemplary sustainable control release fertilizer that may comprise an exemplary natural char / struvite composite. The exemplary sustainable control release fertilizer may comprise a phosphorus pentoxid (P2O5) content in a range of 16 wt% to 25 wt%.

[0009] In an exemplary embodiment, a mole ratio of Mg2+:NH4+:PO43’ in the exemplary sustainable control release fertilizer may be 2: 1: 1. In an exemplary embodiment, a mass ratio of the natural char to the struvite may be 0: 100, 25:75, 50:50, or 75:25.

[0010] One or more exemplary embodiments describe an exemplary method for producing an exemplary sustainable control release fertilizer comprising an exemplary natural char / struvite composite may comprise obtaining an exemplary first solution from an exemplary swage or an exemplary wastewater by mixing the exemplary swage or wastewater with an exemplary acidic solution in an exemplary volume ratio of 1: 10, preparing an exemplary second solution by adding an exemplary chelating agent to the exemplary first solution, obtaining a struvite solution by adding a plurality of magnesium ions to the second solution, producing an exemplary natural char / struvite solution by adding the exemplary natural char to the exemplary struvite solution, increasing an exemplary pH level of the exemplary natural char / struvite solution to 9.00 by adding an exemplary alkaline solution to the exemplary natural char / struvite solution, producing an exemplary sustainable control release fertilizer by extracting and drying the exemplary natural char / struvite composite in a room temperature and at a temperature of 70 °C to 80 °C, respectively.

[0011] In an exemplary embodiment, forming an exemplary first solution containing an exemplary plurality of phosphorus and nitrogen ions with an exemplary pH level of 4.00 may comprise mixing an exemplary swage or wastewater with an exemplary sulfuric acid solution with a pH level of 4:00 and a concentration of 0.2N in an exemplary volume ratio of 1: 10 of the exemplary wastewater to the exemplary sulfuric acid solution. In exemplary embodiment,forming an exemplary struvite solution may comprise adding an exemplary citric acid solution with a concentration of 50% by weight as an exemplary chelating agent to the exemplary first solution. In an exemplary embodiment, producing an exemplary natural char / struvite solution may comprise adding the natural char to the exemplary struvite solution in a mass ratio of 0: 100, 25:75, 50:50, or 75:25. In an exemplary embodiment, an exemplary pH level of an exemplary natural char / struvite solution may be raise to 9.00 by adding an exemplary sodium hydroxide solution with a concentration of 4N to the exemplary natural char / struvite solution.

[0012] This Summary may introduce a number of concepts in a simplified format; the concepts are further disclosed within the “Detailed Description” section. This Summary is not intended to configure essential / key features of the claimed subject matter, nor is intended to limit the scope of the claimed subject matter.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The novel features which are believed to be characteristic of the present disclosure, as to its structure, organization, use and method of operation, together with further objectives and advantages thereof, will be better understood from the following drawings in which an exemplary embodiment will now be illustrated by way of example. It is expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the present disclosure. Exemplary embodiments will now be described by way of example in association with the accompanying drawings in which:

[0014] FIG. 1 illustrates flowchart of an exemplary method for synthesizing an exemplary struvite / natural char composite, consistent with one or more exemplary embodiments of the present disclosure;

[0015] FIG. 2 illustrates scanning electron microscope (SEM) images of (a) an exemplary struvite / natural char composite containing 25 %wt natural char, (b) an exemplary struvite / natural char composite containing 50 %wt natural char, and (c) an exemplarystruvite / natural char composite containing 75 %wt natural char with a magnification of 50 pm, consistent with one or more exemplary embodiments of the present disclosure;

[0016] FIG. 3 illustrates plots of phosphorus accumulative release in a plurality of exemplary struvite / natural char composites containing 0, 25,50, and 75 %wt natural char in (a) deionized water, (b) a hydrochloric acid (HC1) solution, and (c) a citric acid solution, consistent with one or more exemplary embodiments of the present disclosure;

[0017] FIG. 4 illustrates plots of nitrogen accumulative release in a plurality of exemplary struvite / natural char composites containing 0, 25,50, and 75 %wt natural char in (a) deionized water, (b) a hydrochloric acid (HC1) solution, and (c) a citric acid solution, consistent with one or more exemplary embodiments of the present disclosure;

[0018] FIG. 5 illustrates plots of magnesium accumulative release in a plurality of exemplary struvite / natural char composites containing 0, 25,50, and 75 %wt natural char in (a) deionized water, (b) a hydrochloric acid (HC1) solution, and (c) a citric acid solution, consistent with one or more exemplary embodiments of the present disclosure

[0019] FIG. 6 illustrates effect of a plurality of exemplary struvite / natural char composites containing 0, 25,50, and 75 %wt natural char on growth of maize, consistent with one or more exemplary embodiments of the present disclosure;

[0020] FIG. 7 illustrates plots of effect of a plurality of exemplary struvite / natural char composites containing 0, 25,50, and 75 %wt natural char compared to a control as well as triple superphosphate (TSP) on dry matter yield of maize after 81 days in (a) a non-calcareous soil and (b) a calcareous soil, consistent with one or more exemplary embodiments of the present disclosure;

[0021] FIG. 8 illustrates plots of effect of a plurality of exemplary struvite / natural char composites containing 0, 25,50, and 75 %wt natural char compared to a control as well as triple superphosphate (TSP) on a phosphorus content (% P) of maize after 81 days in (a) a non-calcareous soil and (b) a calcareous soil, consistent with one or more exemplary embodiments of the present disclosure;

[0022] FIG. 9 illustrates plots of effect of a plurality of exemplary struvite / natural char composites containing 0, 25,50, and 75 %wt natural char compared to a control as well as triple superphosphate (TSP) on nitrogen content (% N) of maize after 81 days in (a) a non-calcareous soil and (b) a calcareous soil, consistent with one or more exemplary embodiments of the present disclosure;

[0023] FIG. 10 illustrates plots of effect of a plurality of exemplary struvite / natural char composites containing 0, 25,50, and 75 %wt natural char compared to a control as well as triple superphosphate (TSP) on a magnesium content (% Mg) of maize after 81 days in (a) a non- calcareous soil and (b) a calcareous soil, consistent with one or more exemplary embodiments of the present disclosure;

[0024] FIG. 11 illustrates plots of effect of a plurality of exemplary struvite / natural char composites containing 0, 25,50, and 75 %wt natural char compared to a control as well as triple superphosphate (TSP) on a height of maize after 81 days in (a) a non-calcareous soil and (b) a calcareous soil, consistent with one or more exemplary embodiments of the present disclosure;

[0025] FIG. 12 illustrates plots of effect of a plurality of exemplary struvite / natural char composites containing 0, 25,50, and 75 %wt natural char compared to a control as well as triple superphosphate (TSP) on a steam diameter of maize after 81 days in (a) a non-calcareous soil and (b) a calcareous soil, consistent with one or more exemplary embodiments of the present disclosure; and

[0026] FIG. 13 illustrates plots of effect of a plurality of exemplary struvite / natural char composites containing 0, 25, 50, and 75 %wt natural char compared to a control as well as triple superphosphate (TSP) on a chlorophyll content of maize after 81 days in (a) a non-calcareous soil and (b) a calcareous soil, consistent with one or more exemplary embodiments of the present disclosure.DETAILED DESCRIPTION

[0027] In the following detailed description, numerous specific details are set forth by way of examples to provide a thorough understanding of the relevant teachings related to the exemplary embodiments. However, it should be apparent that the present teachings may be practiced without such details. In other instances, well known methods, procedures, components, and / or circuitry have been described at a relatively high-level, without detail, in order to avoid unnecessarily obscuring aspects of the present teachings.

[0028] The following detailed description is presented to enable a person skilled in the art to make and use the methods and devices disclosed in one or more exemplary embodiments of the present disclosure. For purposes of explanation, specific nomenclature is set forth to provide a thorough understanding of the present disclosure. However, it will be apparent to one skilled in the art that these specific details are not required to practice the disclosed exemplary embodiments. Descriptions of specific exemplary embodiments are provided only as representative examples. Various modifications to the exemplary implementations will be plain to one skilled in the art, and the general principles defined herein may be applied to other implementations and applications without departing from the scope of the present disclosure. The present disclosure is not intended to be limited to the implementations shown, but is to be accorded the widest possible scope consistent with the principles and features disclosed herein.

[0029] Disclosed herein is an exemplary cost-effective sustainable control release fertilizer comprising a composite of natural char and struvite that can provide a suitable content of phosphorus for early growths stage of a plant. In an exemplary embodiment, "sustainable control release fertilizer" may refer to a fertilizer that can provide a suitable amount of at least one nutrient, for example, but is not limited to, phosphorus, magnesium, nitrogen, and / or acombination thereof at a determined time to at least one plant at a right stage of plant growth. In an exemplary embodiment, "composite of natural char and struvite", "natural char / struvite composite", and / or "struvite / natural char composite" may refer to a material that is produced by two parts of natural char and struvite in a various mass ratio of the natural char and struvite. In an exemplary embodiment, the "struvite" may refer to a compound made up of magnesium ammonium phosphate with a chemical formula of MgNIUPCU.bHiO from a source of phosphorus, magnesium, and ammonium like swage and / or wastewater. In an exemplary embodiment, the "natural char" may refer to a natural compound with a plurality of compositions as well as characteristics listed in Table. 1 that is available in the nature. Using natural char along with the struvite to produce an exemplary sustainable control release fertilizer may provide some advantageous, for example, but are not limited to, increasing a dissolution rate of phosphorus, providing a suitable amount of phosphorus, magnesium, as well as nitrogen for early growth stage of a plant, preventing phosphorus stabilization in the soil, and providing an appropriate P2O5 content in accordance with a chemical phosphate fertilizer.Table.l: Compositions and Characteristics of the Exemplary Natural CharC 8.08 (%) Pb 0.8 (mg kg'1)N 0.81 (%) Cu 2.3 (mg kg'1)H 0.32 (%) Cd 0 (mg kg'1)K 500 (g kg-1) Surface Area 310 (m2g-1)Na 11-4 (g kg-1) □Ash's Content 8 (%)Fe 200 (mg kg'1) CEC 30 (cmolckg-1)Mn 25 (mg kg'1) EC 0.6 (dS nr1)CEC: Cation Exchange Capacity, EC: Electrical Conductivity.

[0030] In an exemplary embodiment, an exemplary sustainable control release fertilizer may comprise a Mg2+:NH4+:PO43’ mole ratio of 2:1: 1.

[0031] In an exemplary embodiment, a mass ratio of the natural char to exemplary struvite may be varied in ratios of 0: 100, 25:75: 50:50, or 75:25, which can affect a phosphorus content of exemplary sustainable control release fertilizer as well as a phosphorus dissolution rate.

[0032] Disclosed herein further is an exemplary cost-effective method for producing an exemplary sustainable control release fertilizer comprising an exemplary natural char / struvite composite from a wastewater. In an exemplary embodiment, "wastewater" and / or “swage” may refer to a water that contain various substances including phosphorus, nitrogen, magnesium, etc. and the water is produced by community or people's activities like commercial, institutional and public facilities, and / or industrial's activities.

[0033] FIG. 1 illustrates flowchart of exemplary method 100 for producing exemplary sustainable control release fertilizer, consistent with one or more exemplary embodiments of the present disclosure. In an exemplary embodiment, the exemplary method 100 may comprise five main steps. First step (102) may comprise obtaining an exemplary first solution from an exemplary wastewater by mixing the exemplary wastewater with an exemplary acidic solution in an exemplary volume ratio of 1: 10 (the wastewater: the acidic solution). Step 104 may comprise preparing an exemplary second solution by adding an exemplary chelating agent to the exemplary first solution. In next step (step 106), an exemplary struvite solution may be obtained by adding an exemplary plurality of magnesium ions to the exemplary second solution. Step 108 may comprise producing an exemplary natural char / struvite solution by adding the exemplary natural char to the exemplary struvite solution. Then, an exemplary pH level of the exemplary natural char / struvite solution may be increased to 9.00 by adding an exemplary alkaline solution to the exemplary natural char / struvite solution 110. In final step (step 112), the exemplary natural char / struvite composite in a room temperature may be extracted and the exemplary extracted natural char / struvite composite may be dried at a temperature of 70 °C to 80 °C to produce the exemplary sustainable control release fertilizer.

[0034] In further detail with respect to step 102, step 102 may comprise obtaining an exemplary first solution by mixing the exemplary wastewater with an exemplary acidic solution in an exemplary volume ratio of 1: 10. In an exemplary embodiment, the exemplaryfirst solution may comprise a plurality of phosphate and / or magnesium ions with a pH level of4.00. In an exemplary embodiment, the exemplary first solution may be an exemplary sludge extracted from the exemplary wastewater. In an exemplary embodiment, the exemplary sludge may comprise various nutrients, for examples, but are not limited to, phosphorus, nitrogen, and / or magnesium. In an exemplary embodiment, the exemplary acidic solution used for producing the exemplary first solution may be an exemplary sulfuric acid solution. In an exemplary embodiment, the exemplary sulfuric acid solution may be an exemplary sulfuric acid solution with a pH level of 4:00 and a concentration of 0.2N. In an exemplary embodiment, adding the exemplary sulfuric acid solution to the exemplary wastewater may cause producing a plurality of phosphate ions (PO4’3) and ammonium ions (NH4+). In an exemplary embodiment, the exemplary first solution may be obtained after an exemplary first mixing time and an exemplary first stirring speed. In one or more exemplary embodiment, the exemplary first mixing time and stirring speed may be in a range of 60 minutes to 120 minutes and 100 rpm to 150 rpm, respectively.

[0035] In an exemplary embodiment, the method 100 may further comprise an exemplary separating step for separating the exemplary first solution from an exemplary remained wastewater. In one or more exemplary embodiments, the exemplary separating step may comprise filtering an exemplary mixture of the exemplary first solution and the remained wastewater from an exemplary means for filtering. In an exemplary embodiment, the exemplary means for filtering may comprise, for example, but is not limited to, paper, cloth, cotton-wool, asbestos, glass-wool, sand, or other types of porous materials that are well known for those skilled in the art. In a particular embodiment, the means for filtering may be a paper filter. In one or more exemplary embodiments, the exemplary separating step may further comprise centrifugal filtering for separating any remaining residual of wastewater from theexemplary first solution. In an exemplary embodiment, the centrifugal filtering step may be carried out at an exemplary speed in a range of 100 rpm to 200 rpm.

[0036] In further detail with respect to step 104, step 104 may comprise preparing an exemplary second solution by adding an exemplary cheating agent to the exemplary first solution. In an exemplary embodiment, an exemplary citric acid solution may be added to the first solution as the exemplary chelating agent. In one or more exemplary embodiments, an exemplary acid citric concentration may be 50% by weight. The addition of the acid citric as a chelating agent prevents the entry of a plurality of heavy metals as well as other impurities into the exemplary struvite solution.

[0037] In further detail with respect to step 106, step 106 may comprise obtaining an exemplary struvite solution by adding a plurality of magnesium ions to the exemplary second solution. In an exemplary embodiment, the exemplary plurality of magnesium ions may be provided via an exemplary magnesium ionic compound. In an exemplary embodiment, the exemplary magnesium ionic compound may comprise, for example, but is not limited to, magnesium chloride, magnesium sulfate, or a combination thereof.

[0038] In further detail with respect to step 108, step 108 may comprise producing an exemplary natural char / struvite solution by adding the exemplary natural char to the exemplary struvite solution. In an exemplary embodiment, the natural char may be added to the exemplary struvite solution in a mass ratio of 0: 100, 25:75, 50:50, and / or 75:25. In an exemplary embodiment, the natural char / struvite solution may be mixed in an exemplary second mixing time and an exemplary second stirring speed. In an exemplary embodiment, the exemplary second mixing time may be in a range of 30 minutes to 40 minutes and the exemplary second stirring speed may be in a range of 100 rpm to 150 rpm.

[0039] In an exemplary embodiment, the method 100 may further comprise resting the exemplary natural char / struvite solution for an exemplary resting time in an exemplary restingtemperature. In an exemplary embodiment, the exemplary resting time and the resting temperature may be at least 24 hours and a room temperature, respectively.

[0040] In further detail with respect to step 110, step 110 may comprise increasing an exemplary pH level of the exemplary natural char / struvite solution by adding an exemplary alkaline solution to the exemplary natural char / struvite solution. In an exemplary embodiment, the exemplary pH level of the exemplary natural char / struvite may be increased to 9.00 for preparing an exemplary forming condition of an exemplary natural char / struvite composite. In an exemplary embodiment, an exemplary sodium hydroxide may be used as the exemplary alkaline solution to increase the exemplary pH level. In an exemplary embodiment, a concentration of the exemplary sodium hydroxide may be 4N.

[0041] In further detail with respect to step 112, step 112 may comprise extracting the exemplary sustainable control release fertilizer by extracting the exemplary natural char / struvite composite in a room temperature and drying the exemplary extracted struvite / natural char composite at a temperature of 70 °C to 80 °C. In an exemplary embodiment, the extracting the exemplary struvite / natural char composite may comprise precipitating the exemplary natural char / struvite composite in a room temperature and centrifuging the exemplary precipitated struvite / natural char composite in an exemplary predetermined centrifuge speed. In an exemplary embodiment, the predetermined centrifuge speed may be in a range of 100 rpm to 200 rpm. In an exemplary embodiment, the exemplary extracted struvite / natural char composite may be dried at an exemplary predetermined drying time. In an exemplary embodiment, the exemplary predetermined time may be in a range of 40 minutes to 50 minutes.EXAMPLES

[0042] Hereinafter, one or more exemplary embodiments will be described in further detail with reference to examples. It will be obvious to a person having ordinary skill in the artthat these examples may be for illustrative purposes only and are not to be interpreted to limit the scope of the present disclosure.Example 1: Synthesis of Struvite / Natural Char Composite

[0043] In this example, exemplary struvite / natural char composite were synthesized based on an exemplary process similar to method 100. To synthesize exemplary struvite / natural char composite, first an exemplary first solution containing a plurality of phosphate and nitrogen ions with a pH level of 4.00 may be prepared. In an exemplary embodiment, an exemplary struvite / natural char composite may be prepared by mixing a sludge prepared from a swage and a sulfuric acid with a concentration of 0.2N, followed by stirring at about 100-150 rpm for about 90 minutes at a room temperature. Following that, the prepared first solution may be separated from the remained sludge by filtering the mixture of the first solution and remained sludge utilizing a filter paper. Then, the filters first solution may be centrifuged to separate any residual of sludge in a centrifuge speed of 100 to 200 rpm.

[0044] Afterwards, an exemplary second solution may be produced by adding the exemplary citric acid solution with a concentration of 50% wt as a chelating agent to the exemplary first solution. Following that, an exemplary struvite solution may be obtained by adding magnesium chloride solution as a provider of magnesium ions to the exemplary second solution. Then, an exemplary natural char / struvite solution with different ratio of the natural char and struvite may be prepared by adding the exemplary natural char to the exemplary struvite solution in various mass ratio including 0: 100, 25:75, 50:50, and 75:25 (the natural char: the struvite). Following that, the prepared natural char / struvite solution may be mixed for 30 minutes to 40 minutes at a stirring speed of 100 to 150 rpm. Afterward, the natural char / struvite solution may be rested for at least 24 hours at a room temperature.

[0045] Then, a pH level of the exemplary natural char / struvite solution may be raised to9.00 by adding an exemplary sodium hydroxide with a concentration of 4.00 N. Following that, the exemplary natural char / struvite composite may be extracted by precipitating the exemplary natural char / struvite composite in a room temperature and centrifuging the exemplary precipitated struvite / natural char composite in a centrifuge speed of 100 to 200 rpm. Then, the extracted natural char / struvite composite may be dried at a temperature of 70 °C to 80 °C for 40 minutes to 50 minutes. The natural char / struvite composite as a sustainable control release fertilizer with various mass ratio of the struvite to the natural char listed in Table.2.Table.2: Produced Natural Char / Struvite Composites with Various Mass ratio of the Struvite and the Natural CharExample 2: Characterization of Struvite / Natural Char Composites

[0046] In this example, exemplary produced struvite / natural char composites in “Example 1” were characterized by scanning electron microscopy (SEM) and X-ray fluorescence (XRF). Furthermore, a total content of phosphorus (P), magnesium (Mg), and nitrogen (N), heavy metal, pH, and salinity index (SI) of exemplary produced struvite / natural char composites were determined. Also, exemplary struvite / natural char composites' solubility as well as nutrients release (P, N, and Mg) of exemplary struvite / natural char composites were evaluated in deionized water, HCL, and 20g / L citric acid.

[0047] The phosphorus recovery from the sludge according to the exemplary method 100 was calculated via following equation: 100where Pinitiai and PFinai denote the sludge's phosphorus concentrations at the beginning and end of the exemplary producing method 100 of the exemplary struvite / natural char composites. The results show that by adding the natural char to the struvite the phosphorus recovery increase such that the phosphorus recovery from the sludge were 92, 93, 96, and 97% for St, St / NCh 25, St / NCh 50, and St / NCh 75, respectively.

[0048] A total content of phosphorus (P), magnesium (Mg), and nitrogen (N), pH, and salinity index (SI) of exemplary produced struvite / natural char composites with various mass ratio of the exemplary natural char are listed in Table.3. As illustrated in Table.3, a phosphorus content of St / NCh 25, St / NCh 50, and St / NCh 75 are 11, 10, and 7 % by weight, respectively.Table.3: Characteristics of the Struvite / Natural Char CompositesStr 12.67 8.40 9.88 1.20 4.74 7.48 3.15St / NCh 25 11.12 7.93 8.31 0.60 6.60 7.17 4.38St / NCh 50 10.08 6.50 7.00 1.20 8.12 7.12 5.39St / NCh 75 7.25 5.20 6.69 1.91 9.64 7.10 6.40

[0049] On the other hand, the heavy metals and their concentrations in the exemplary produced struvite / natural char composites were determined and the results were listed in Table.4. The exemplary produced St / NCh composites contain minimal amounts of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), and arsenic (As) that confirms the concentration of heavy metals in the produced struvite / natural char composites is lower than the acceptable limit for the fertilizers.Table.4: Heave Metals Concentration of the Struvite / Natural Char CompositesCd Pb Cu Zn As Mo Ni mg / kgStr 2.80 7.00 16.00 900.00 29.30 0.55 13.00St / NCh 25 2.50 11.00 48.00 1276.00 34.30 0.62 20.00St / NCh 50 2.50 29.00 53.00 1458.00 35.30 0.73 23.00St / NCh 75 3.10 52.00 72.00 1448.00 38.60 2.50 25.00Permissible Concentration Limit of „„ , „„ „„ „„ , „„ „„ , „„ „„ u Heavy M A .e .tal .s i •n F .2ertilizer (Muys et al 1.2u217)-. 60.00 120.00 600.00 1500.00 40.00 - 100.00

[0050] Furthermore, the chemical characteristics of exemplary produced struvite / natural char composites based on XRF analysis were listed in Table.5.Table.5: Chemical Characteristics of Struvite / Natural Char Composites l it >2 CaO K2O SO3NazO MgO l eztb P2O5 BaO AI2O3 SiO2(’ / •)St <0.05 14.77 1 / 59 1.38 1.45 16.51 2.77 28.19 0.05< 1.05 0.53St / NCh 25 0.09 5.56 0.50 4.54 2.21 15.11 0.87 24.50 0.05 < 3.25 3.89St / NCh 50 0.20 7.23 1.00 0.64 1.66 13.21 2.23 23.00 0.05 < 6.22 1.23St / NCh 75 0.29 9.58 1.59 2.06 1.45 10.71 2.77 16.32 0.05< 9.58 1.76

[0051] Additionally, the produced exemplary composites (St / NCh 25, St / NCh 50, andSt / NCh 75) indicate a plurality of particles with morphology of irregular shapes in a form of round and rod- shaped (Fig. 2).

[0052] The phosphorus, nitrogen, and magnesium solubility of exemplary struvite / natural char composites in deionized water, HC1 0.5M, and 20g / L citric acid are illustrated in Table.6, Table.7, and Table.8, respectively. The results indicate a highest solubility of phosphorus , nitrogen, and magnesium were occurred in HC1 0.5M, though these elements (P, N, Mg) solubility is very low in deionized water due to a lower pH level of HCL compared to the deionized water.Table.6: Phosphorus Solubility of the Produced Struvite / Natural Char Composites in H2O, 20 g / L Citric_ Acid, and HC10.5 M _H2O 20 g / L Citric Acid HC10.5 MDissolution rate Dissolution rate Dissolution rate

[0053] As illustrated in Table.6, P% in water is 1.40, 1.48, and 2.00 for St / NCh 25, St / NCh 50, St / NCh 75, respectively. While, a dissolution rate of phosphorus of the exemplary struvite in HC1 0.5M and 20g / L citric acid were 82% and 62%, respectively and by adding the natural char to the struvite as well as raising a natural char mass ratio, the phosphorus 's dissolution rate increased.Table.7: Nitrogen Solubility of the Produced Struvite / Natural Char Composites in H2O, 20 g / L Citric _ Acid, and HC10.5 M _H2O 20 g / L Acid citric HC10.5 MDissolution rate Dissolution rate Dissolution rate(7.) (g / L) (7.) (g / L) (7.) (g / L)Str 5.5000 0.0460 20.4100 0.1700 27.3200 0.2300St / NCh 25 6.0400 0.0480 24.0600 0.1900 32.5400 0.2600St / NCh 50 7.6300 0.0500 30.9100 0.2000 43.7100 0.2800St / NCh 75 11.3000 0.0590 41.8700 0.2200 59.9700 0.3100

[0054] Furthermore, a nitrogen solubility of struvite (St) in deionized water, HC1 0.5M, and 20g / L citric acid were 5.5%, -21%, and -28%, respectively. While, a solubility of nitrogen was increased by adding the natural char as well as increasing the mass ratio of the natural char in the struvite composites. As illustrated in Table.7, the dissolution rate of the nitrogen in deionized water were 6%, 7%, and 11% for the exemplary St / NCh 25, St / NCh 50, and St / NCh 75, respectively. On the other hand, the exemplary St / NCh 75 indicates a heights amount of nitrogen solubility in HC10.5M and 20g / L citric acid.Table.8: Magnesium Solubility of the Produced Struvite / Natural Char Composites in H20, 20 g / L Citric _ Acid, and HC10.5 M _H2O 20 g / L Acid citric HC10.5 MDissolution rate Dissolution rate Dissolution rate(7.) (g / L) (7.) (g / L) (7.) (g / L)Str 1.4500 0.0096 67.710 0.4464 98.3000 0.6480St / NCh 25 2.5900 0.0140 75.3000 0.4176 99.5900 0.5500St / NCh 50 3.0800 0.0140 78.1000 0.3648 99.7600 0.4600St / NCh 75 3.2200 0.0140 81.8000 0.3648 100.0000 0.4400

[0055] Additionally, a magnesium solubility's results of the exemplary struvite / natural char composites as represented in Table.8. As can be seen, by increasing the mass ration of the natural char, the magnesium solubility was increased. As well as, the magnesium solubility in HC1 0.5M and deionized water showed a highest and lowest amount, respectively.

[0056] An exemplary accumulative release of P, N, and Mg in the exemplary struvite / natural char composites in deionized water (a), HC1 0.5M (b), and 20 g / L citric acid (c) are demonstrated in Fig. 3, Fig 4, and Fig. 5, respectively. As illustrated in Fig 3-Fig.5, by increasing a contact time (1-84 days), the accumulative release of these three elements (P, N, and Mg) in water, HC1 0.5M as well as 20 g / L citric acid increased. Furthermore, the accumulative release of P, N, and Mg has increased in accordance with increase in the massratio of the natural cha. An exemplary highest accumulative release of phosphorus, nitrogen, and magnesium was obtained in HC10.5M.

[0057] As illustrated in Fig.3a, the accumulative release of P for the St / NCh 25, St / NCh 50, and St / NCh 75 in deionized water after 84 days depositions of the exemplary composite are 6%, -8%, and -10%, respectively. While, the P accumulative release of the St / NCh 25, St / NCh 50, and St / NCh 75 reaches 90%, 92, 94%, respectively in HC1 0.5 after 84 days depositions of the exemplary composites (Fig. 3b).

[0058] Furthermore, as can be seen in Fin.4a, an exemplary accumulative release of nitrogen for the struvite (St), and the St / NCh 25, St / NCh 50, and St / NCh 75 in deionized water after 84 days deposition reach to 11.4%, 13.89%, 23.14%, and 15.68%, respectively. Also, an exemplary accumulative release of N after 84 days for these four produced fertilizers is 78%, 80%, 84.55%, and 98% in citric acid, respectively (Fig.4c). Although, HC1 0.5M indicates a highest accumulative release of nitrogen at the 84-day that is more than 99%.

[0059] The results of Fig.5a-c illustrate that the accumulative release of magnesium from the all produced fertilizers (St, St / NCh 25, St / NCh 50, St / NCh 75) reaches to more than 94% in HC1 at the 84-day. In addition, the magnesium accumulative release in citric acid (20g / L) after 84 days reaches to 65%, 73%, 86%, and 87% for the St, St / NCh 25, St / NCh 50, and St / NCh 75, respectively. Furthermore, the St / NCh 25, St / NCh 50, and St / NCh 75 indicate an exemplary accumulative of 3.98%, 4.5%, 5.07%, and 6.60, respectively in deionized water.Example 3: Greenhous Experiment Set Up

[0060] The effect of the produced exemplary struvite / natural char with various mass ratio of the exemplary natural char on the growth as well as the nutrients uptake indices of maize in a non-calcareous soil and a calcareous soil after 81 days was investigated. The effect of the exemplary struvite / natural char composites was compared to a control as well as the triple phosphate fertilizer

[0061] The effect of the exemplary struvite / natural char composites containing 25%, 50%, and 75% the natural char as well as the control on growth of maize are illustrated in Fig.6. As illustrated in Fig.6, the symptoms of phosphorus deficiency in control compared to the exemplary struvite / natural char composites was observed, which observed in the form of the leaves purple margin.

[0062] Furthermore, the results of effect of the exemplary struvite / natural composites containing 0%, 25%, 50%, and 75% the natural char, control as well as TPS on the nutrients uptake indices (%P, %N, and %Mg) by maize after 81 days planting in the non-calcareous soil (a) and a calcareous soil (b) were illustrated in Figs 8-10. As illustrates in these figures, the maize's phosphorus content, the maize's nitrogen content as well as maize's magnesium content that were treated with the exemplary composites containing natural char are more than the TPS and control, respectively and significant differences was observed (Table.9). On the other hand, the effect of the exemplary struvite / natural char composites on the nutrients uptakes is as following: St / NCh 75> St / NCh 50> ST / NCh 25> St.Table.9: Statistical significance of the Exemplary Struvite / Natural Char Composites in two types of soil and the Exemplary Struvite / Natural Char Composites interactions on for Variables in a Two-Way ANOVA Analysis MSDry P- %N P- Height %Mg SPAD Leaves SteamVariables dfMatter Concentration Uptake (cm) Value Number Diameter(g / pot) (mg / g) (mg / kg) (mm)Soil 1 58.88"* 0.006"* 0.520"* 172.55"* 155.23"* 0.055*" 0.83* 1.46*" 5.10*"Composites (C) 9 85.25"* 0.0018"* 1.176"* 307.63" 374.23"* 0.084*" 49.88"* 2.75*" 9.01*"SXC 9 1.34" 0.000"* 0.009"* 2.63* 8.94* 0.001 4.10*" 0.056 0.06*Error 40 1.07 0.000 0.003 1.79 5.06 0.002 0.383 0.070 0.070Total 60Significance effect: *p<0.05, **p<0.01, ***p<0.001

[0063] In addition, the effect of the exemplary produce composites (St / NCh 75 > St / NCh 50> ST / NCh 25> St), control, and triple phosphate on an exemplary dry matter, height, steam diameter, and SPAD value after 81 days planting of maize in the non-calcareous soil (a) and a calcareous soil (b) were illustrated in Fig.7, Fig.ll, Fig.12, and Fig.13, respectively. Theresults confirmed that the dry matter, height, steam diameter, and SPAD value follow the same trend as the results of the nutrients uptakes (Fig.7, Fig.ll, Fig.12, Fig.13, and Table.9). Furthermore, the growth and nutrients uptake indices in the non-calcareous soil were greater than the calcareous soil due to their composition differences of two types of soil. The presence of a high amount of calcium in the calcareous soil can cause production of the deposited calcium phosphate, so the P absorption decrease compared to the non-calcareous soil.

[0064] All these results show that the presence of the natural char along with the struvite as a composite can significantly enhance plant's growth conditions.

[0065] While the foregoing has described what are considered to be the best mode and / or other examples, it is understood that various modifications may be made therein and that the subject matter disclosed herein may be implemented in various forms and examples, and that the teachings may be applied in numerous applications, only some of which have been described herein. It is intended by the following claims to claim any and all applications, modifications and variations that fall within the true scope of the present teachings.

[0066] Unless otherwise stated, all measurements, values, ratings, positions, magnitudes, sizes, and other specifications that are set forth in this specification, including in the claims that follow, are approximate, not exact. They are intended to have a reasonable range that is consistent with the functions to which they relate and with what is customary in the art to which they pertain.

[0067] The scope of protection is limited solely by the claims that now follow. That scope is intended and should be interpreted to be as broad as is consistent with the ordinary meaning of the language that is used in the claims when interpreted in light of this specification and the prosecution history that follows and to encompass all structural and functional equivalents. Notwithstanding, none of the claims are intended to embrace subject matter that fails to satisfythe requirement of Sections 101, 102, or 103 of the Patent Act, nor should they be interpreted in such a way. Any unintended embracement of such subject matter is hereby disclaimed.

[0068] Except as stated immediately above, nothing that has been stated or illustrated is intended or should be interpreted to cause a dedication of any component, step, feature, object, benefit, advantage, or equivalent to the public, regardless of whether it is or is not recited in the claims.

[0069] It will be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein. Relational terms such as first and second and the like may be used solely to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between such entities or actions. An element proceeded by “a” or “an” does not, without further constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0070] Unless otherwise stated, all measurements, values, ratings, positions, magnitudes, sizes, and other specifications that are set forth in this specification, are approximate, not exact. They are intended to have a reasonable range that is consistent with the functions to which they relate and with what is customary in the art to which they pertain.

[0071] It will be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study, except where specific meanings have otherwise been set forth herein. Relational terms such as “first” and “second” and the like may be used solely to distinguish one entity or action from another without necessarily requiring or implying any actual such relationship or order between such entities or actions.

[0072] The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it may be seen that various features are grouped together in various implementations. This is for purposes of streamlining the disclosure, and is not to be interpreted as reflecting an intention that the claimed implementations require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed implementation. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.While various implementations have been described, the description is intended to be exemplary, rather than limiting and it will be apparent to those of ordinary skill in the art that many more implementations and implementations are possible that are within the scope of the implementations. Although many possible combinations of features are shown in the accompanying figures and discussed in this detailed description, many other combinations of the disclosed features are possible. Any feature of any implementation may be used in combination with or substituted for any other feature or element in any other implementation unless specifically restricted. Therefore, it will be understood that any of the features shown and / or discussed in the present disclosure may be implemented together in any suitable combination. Accordingly, the implementations are not to be restricted except in light of the attached claims and their equivalents. Also, various modifications and changes may be made within the scope of the attached claims.

Claims

What is claimed is:

1. A sustainable control release fertilizer comprising a natural char / struvite composite wherein a phosphorus us pentoxid content of the sustainable control release fertilizer is in a range of 16 wt% to 25 wt%.

2. The sustainable control release fertilizer of claim 1, wherein a mol ratio of Mg2+:NH4+:PO43’ in the sustainable control release fertilizer is 2: 1: 1.

3. The sustainable control release fertilizer of claim 1, wherein a mass ratio of the natural char to the struvite comprises 0:100, 25:75, 50:50, or 75:25.

4. A method for producing a sustainable control release fertilizer of any one of claims 1 to 3 from a wastewater or swage comprising following steps: obtaining a first solution containing a plurality of phosphorus and nitrogen ions with a pH level of 4.00 from a swage or wastewater by mixing a swage or wastewater with a sulfuric acid solution with a pH level of 4:00 and a concentration of 0.2N wherein a volume ratio of the swage or wastewater to the sulfuric acid solution is 1: 10; preparing a second solution by adding a citric acid solution (50% by weight) to the first solution; obtaining a struvite solution by adding a plurality of magnesium ions to the second solution; producing a natural char / struvite solution by adding the natural char to the struvite solution in a mass ratio of 0:100, 25:50, 50:50, or 75:25; increasing a pH level of the natural char / struvite solution to 9.00 by adding a sodium hydroxide solution with a concentration of 4N to the natural char / struvite solution; andproducing the sustainable control release fertilizer by extracting the natural char / struvite composite in a room temperature and drying the extracted natural char / struvite composite at a temperature of 70 °C to 80 °C.

5. A method for producing a sustainable control release fertilizer of any one of claims 1 to 3 from a wastewater comprising following steps: obtaining a first solution from a swage or wastewater by mixing a swage or wastewater with an acidic solution in a volume ratio of 1: 10 (the swage or wastewater: the acidic solution); preparing a second solution by adding a cheating agent to the first solution; obtaining a struvite solution by adding a plurality of magnesium ions to the second solution; producing a natural char / struvite solution by adding the natural char to the struvite solution; increasing a pH level of the natural char / struvite solution to 9.00 by adding an alkaline solution to the natural char / struvite solution; extracting the sustainable control release fertilizer by extracting the natural char / struvite composite in a room temperature and drying the extracted natural char / struvite composite at a temperature of 70 °C to 80 °C.

6. The method of claim 5, wherein the first solution comprises a plurality of phosphorus and nitrogen ions with a pH level of 4.00.

7. The method of claim 5, wherein the acidic solution is a sulfuric acid solution with a pH level of4:00 and a concentration of 0.2N.

8. The method of claim 5, wherein the chelating agent is an acid citric concentration with a concentration of 50% by weight.

9. The method of claim 5, wherein a mass ratio of the natural char to the struvite solution is 0: 100, 25:75, 50:50, or 75:25.

10. The method of claim 5, wherein the alkaline solution is a sodium hydroxide solution with a concentration of 4N.

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