This work was designed to produce microparticle composite systems from Moringa oleifera seed powder and clay microparticles (CMPs) for use in water treatment applications. Adsorption and immobilization of M. oleifera cationic protein (MOCP), obtained from the seed powder, onto core anionic CMP was carried out in a batch process. The CMP was incubated with MOCP and the formulated composite microparticle system was then resuspended in solutions of varying ionic strengths and conductivity was measured to determine the adsorption of MOCP onto CMP. The results generally showed an increase in the conductivity with increased ionic strength up to 0.8 M NaCl, after which the conductivity decreased. The MOCP-treated CMP and untreated CMP were characterized using Fourier transform infrared spectroscopy and X-ray diffraction measurements and results showed differences in the absorbance and morphological features of treated CMP as compared to untreated CMP which further suggests adsorption and flocculation tendencies of the composite system. Flocculation capabilities of the formulated composites were studied by UV–visible spectrophotometry. The formulated composite system was found to be an environmentally friendly water treatment chemical since it is derived from locally sustainable natural products.

INTRODUCTION

While over 70% of the Earth's surface is covered by water, most of it is unusable for human consumption. Developing countries face increasing challenges in obtaining clean potable water as water bodies are becoming heavily polluted owing to rising urban populations and industrialization (Moreno 2009). Hence, there is a great need for some form of purification of water from all sources before consumption, as safe drinking water is essential to the health and welfare of mankind. However, current methods of water treatment involving coagulation/flocculation, adsorption, filtration and, finally, chlorination are costly (Jones et al. 2007).

Synthetic coagulants, such as aluminium sulphate (alum), have been widely used in water treatment for coagulation–flocculation processes around the world. Due to challenges associated with the use of alum (mostly high costs and certain health effects), there is a great demand for alternative coagulants of natural origin, which are efficient, cost effective, readily available and non-toxic (Bhatia et al. 2007; Bhuptawat et al. 2007; Ali et al. 2010b). The removal of toxic organic and inorganic contaminants from raw water rapidly, efficiently and within reasonable cost is, therefore, essential and has become an important technological challenge. It is necessary to explore new water purification techniques by finding natural alternatives for water coagulants to treat turbid waste water (Ali et al. 2009).

Numerous systems with increased affinity, capacity and selectivity for heavy metals and other contaminants are in various stages of research and development. The benefits from use of these systems may derive from their enhanced reactivity, surface area and sequestration characteristics (Berger 2008).

In terms of water treatment applications, Moringa oleifera seed, in diverse extracted and purified forms, has been demonstrated to remove suspended materials (silt, clay, bacteria, etc.), generate reduced sludge volumes in comparison to alum, soften hard water and act as an effective absorber of cadmium (Bhuptawat et al. 2007; Beltran-Heredia & Sanchez-Martin 2009; Ali et al. 2010a). Although M. oleifera can be utilized to treat water to reduce turbidity, additional treatment technologies are necessary to achieve its full potential.

Composite systems comprising polymer molecules and natural or layered minerals like clays can be prepared by adjusting the interaction enthalpy between all components. The use of clays as building blocks for assembling organic species yields useful hybrid structured materials (Rytwo 2012). The use of such microparticle systems combines the advantages of coagulant and flocculant by neutralizing the charge of the suspended particles while bridging between them and anchoring them to a denser particle (clay mineral), enhancing precipitation (Rytwo 2012). This research work will focus on the formulation of microparticle composite systems of M. oleifera/clay and evaluate the effectiveness and suitability of these composite systems for household water treatment applications.

MATERIALS AND METHODS

Materials

Dry M. oleifera seeds and clay were obtained from a farmer in Yola town, Nigeria. Sodium chloride (NaCl) was obtained from British Drug House Chemical Laboratories Ltd, UK was used as supplied without further purification.

Dry M. oleifera seeds were screened so that only mature seeds showing no signs of discoloration, softening or extreme desiccation were used for experimentation. The selected seeds were used for preparation of microparticles.

Preparation of microparticles of Moringa oleifera and clay

Preparation of microparticles was carried out using a solid-state process. Twenty grams of dried seed kernel of M. oleifera was milled into a fine micro-sized powder and sieved using a 400-μm mesh screen to obtain active ingredients in the seeds. A stock of the M. oleifera seed powder (MOSP) was kept in a cool, dry place, from which appropriate quantities were taken for experimentation. Clay was ground into fine microparticle sizes, using a mortar and pestle, and sieved using an 800-μm mesh screen. A stock was stored prior to the adsorption process.

Extraction of water soluble cationic protein from Moringa oleifera

Extraction of water soluble cationic proteins from M. oleifera seeds into the aqueous phase was carried out as described by Huda et al. (2012). In brief, 1.0 g MOSP was suspended in a 20 ml polypropylene centrifuge tube containing deionized water. The centrifuge tube was placed horizontally on a slow roller for 1 hour at room temperature to allow cationic protein to dissolve in the water. The tube was then turned upright to allow heavy matter to settle to the bottom. The supernatant, now containing M. oleifera cationic protein (MOCP), was then collected and this concentrated solution was used unfiltered. This procedure was repeated for 0.8 g, 0.6 g, 0.4 g and 0.2 g MOSP.

MOCP adsorption onto clay microparticles

One gram of clay microparticles (CMPs) was suspended in distilled water. Ten millilitres of supernatant containing 1.0 g MOCP (25 mg/ml crushed seeds in deionized water) was pipetted into the test-tube containing the CMP. The mixture so formed was rolled for 1 hour in a 20 ml centrifuge tube. The sample was then centrifuged for 5 minutes in a standard bucket centrifuge to pellet of coated particles. The supernatant was removed and the particles resuspended in deionized water with centrifugation. This process was repeated three times to adequately remove excess biochemical oxygen demand from the suspension (Huda et al. 2012).

Adsorption test

Conductivity measurement

Adsorption of the cationic protein onto the anionic CMPs was determined by carrying out conductivity measurement of the microparticles before and after treatment with MOCP solution. The MOCP/clay composite system was resuspended in various ionic strengths of NaCl and the conductivity measured using Accumet Basic Fisher Scientific AB30 conductivity meter.

Before and after treatment with MOCP solution, the CMPs were investigated using Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) measurements to determine the adsorption/coating of CMP by MOCP and flocculation propensity.

FTIR measurements

In order to investigate the evidence of adsorption and flocculation propensity, the infra-red spectra of the formulated composite system under investigation were measured from 4,000 cm−1 to 600 cm−1. The spectral readings were taken using a FTIR spectrometer (Thermo NICOLET IR-100 Series) and the results were subsequently interpreted.

XRD measurement

The XRD measurement of microparticles and microparticle composite systems were evaluated with a Rigaku Geigerflex diffractometer. The dry sample of microparticles was mounted on a sample holder, and the patterns recorded in the range of 0–50 ° at the speed of 5 °/min. The crystalline colloidal particle was calculated from the width of the XRD peaks, using the Debye–Scherrer formula: 
formula
where D is the average crystallite domain size perpendicular to the reflecting planes, λ is the X-ray wavelength, β is full width at half maximum and θ is the diffraction angle.

Flocculation efficiency test of composites

Flocculation efficiency tests were carried out on the formulated MOCP/CMP composite systems, as outlined by Alang et al. (2011), to investigate their ability to clarify synthetic turbid water. Synthetic turbid water was made by adding 5.0 g of kaolin powder to 1.0 litre of water, and the solution stirred for 1 hour using a magnetic stirrer before allowing the slurry to settle and then used for the study. Ultraviolet spectrophotometry was used to monitor the flocculation abilities through absorbance measurements, using a range of 200–600 nm wavelengths. The absorbance values [A = log(I0/I)] of untreated water was measured with the UV-spectrophotometer (HELIOS ZETA v8.00) prior to treatment with flocculants. The UV-spectrophotometer was calibrated with distilled water (blank determination) and then 0.2 g of each of the test products was added to 100 ml of untreated water and the absorbance measured at intervals of 10 minutes for 90 minutes. The absorbance of the now treated water was then measured after 24 hours. This was done in order to observe the effect of time on flocculation efficiency. The flocculation efficiency of each product was calculated using the formula: 
formula
where A0 is the absorbance of synthetic turbid water sample and Af is the absorbance of the clarified supernatant water. The efficiency of each product to clarify raw water was calculated after 1.5 hours and 24 hours of reaction time.

RESULTS AND DISCUSSION

Characterization of MOCP/CMP composite systems

FTIR analysis

FTIR was used to analyse the CMPs before and after treatment with MOCP solution at various concentrations to investigate evidence of adsorption and flocculation propensity. The FTIR spectra of CMPs before treatment and after treatment with various concentrations of MOCP solution are shown in Figures 17 for corresponding peak areas for specific regions that give the functional groups present attributed to stretching and bending vibrations.
Figure 1

IR spectra of CMP.

Figure 1

IR spectra of CMP.

Figure 2

IR spectra of 0.2 g MOCP in CMP.

Figure 2

IR spectra of 0.2 g MOCP in CMP.

Figure 3

IR spectra of 0.4 g MOCP in CMP.

Figure 3

IR spectra of 0.4 g MOCP in CMP.

Figure 4

IR spectra of 0.6 g MOCP in CMP.

Figure 4

IR spectra of 0.6 g MOCP in CMP.

Figure 5

IR spectra of 0.8 g MOCP in CMP.

Figure 5

IR spectra of 0.8 g MOCP in CMP.

Figure 6

IR spectra of 1 g MOCP in CMP.

Figure 6

IR spectra of 1 g MOCP in CMP.

Figure 7

IR spectra of 1 g MOCP.

Figure 7

IR spectra of 1 g MOCP.

Evidence of adsorption

The IR spectra (Figures 17) and Table 1 show that there are differences in the absorbance features of treated and untreated CMPs, demonstrating the expected adsorption of MOCP onto CMPs, as well the flocculation tendencies. Some of these features are discussed below:

  • (i) The IR spectra for CMP-treated MOCP all contain broad peaks at 3,443.15 cm−1, 3,450.42 cm−1, 3,425.45 cm−1, 3,450.07 cm−1 and 3,450.25 cm−1; these peaks are associated with the adsorption of –NH groups from protein constituents in M. oleifera, in addition to other functional groups in the natural product. This provides ample evidence that adsorption of MOCP onto CMP must have occurred, thus confirming reports in the literature that when MOSP is dissolved in water, it releases water-soluble proteins which are positively charged polyelectrolytes. This cationic nature can be attributed to the protonation of the amine functional group of the protein which, thus, attracts negatively charged particles such as clay, silt, bacteria and other impurities leading to flocculation (Folkard et al. 1993, 1999).

  • (ii) The lowering, broadening and shifting of the absorption at peaks 3,443.15 cm−1, 3,450.42 cm−1, 3,425.45 cm−1, 3,450.07 cm−1 and 3,450.25 cm−1, as seen in samples A–E (CMP treated with MOCP at different concentrations), as compared to sample F (untreated CMP), corresponds to –NH bond absorption bands, which suggests the replacement of –OH groups by –NH groups in the process of adsorption (Alang et al. 2011). Also, the absorption bands suggest an increase in the amount of MOCP adsorbed onto the CMP, which is consistent with the expected adsorption.

  • (iii) The peak at 2,372.85 cm−1 in untreated CMP spectra, corresponding to nitrile group (C≡N), shifted and there was an increase in intensity of peaks at 2,371.06 cm−1, 2,371.73 cm−1, 2,371.89 cm−1, 2,371.95 cm−1 and 2,372.06 cm−1 for treated CMP samples. This may be as a result of oxidation of the amine groups, showing the expected adsorption (Alang et al. 2011). All treated CMP sample spectra showed absorption peaks of the nitrile group as well as the N-H group, which is key to the flocculation qualities of the sample products.

  • (iv) The weak peak in the CMP spectra at 1,662.90 cm−1 for –COOH groups shifted to sharp intense peaks at 1,631.99 cm−1, 1,632.51 cm−1, 1,627.20 cm−1, 1,653.25 cm−1 and 1,632.20 cm−1 in MOCP-treated CMP sample spectra; these are within range of vibrations in amines and amides of proteins, which further suggests adsorption.

Table 1

FTIR spectroscopic bands of CMPs treated with different amounts of MOCP suspensiona

Bands Sample A (cm−1Sample B (cm−1Sample C (cm−1Sample D (cm−1Sample E (cm−1Sample F (cm−1Sample G (cm−1Assignment 
3,443.15 3,450.42 3,425.45 3,450.07 3,450.25 3,416.76 3,302.49 O-H Stretching, H-bonded 
2,926.62 – 2,925.82 2,926.95 2,924.70 2,924.50 2,926.79 C-H Asymmetric/symmetric stretching 
2,371.06 2,371.73 2,371.89 2,371.95 2,372.05 2,372.85 – C≡N Stretching 
– – 1,745.45 – – – 1,744.07 C=O Stretching in carbonyl of ester 
1,631.99 1,632.51 1,627.20 1,653.25 1,632.20 – 1,664.62 C=O Stretching amide I of protein 
– – 1,469.95 – – – 1,453.95 C-H Scissoring and bending for methylene 
– – – – – – 1,119.71 C-O Stretching due to ether 
– – 1,002.54 – 1,004.05 1,037.18 1,061.10 C-O Stretching due to ether group 
– – 763.42 – – 755.95 798.13 C-H Rocking 
Bands Sample A (cm−1Sample B (cm−1Sample C (cm−1Sample D (cm−1Sample E (cm−1Sample F (cm−1Sample G (cm−1Assignment 
3,443.15 3,450.42 3,425.45 3,450.07 3,450.25 3,416.76 3,302.49 O-H Stretching, H-bonded 
2,926.62 – 2,925.82 2,926.95 2,924.70 2,924.50 2,926.79 C-H Asymmetric/symmetric stretching 
2,371.06 2,371.73 2,371.89 2,371.95 2,372.05 2,372.85 – C≡N Stretching 
– – 1,745.45 – – – 1,744.07 C=O Stretching in carbonyl of ester 
1,631.99 1,632.51 1,627.20 1,653.25 1,632.20 – 1,664.62 C=O Stretching amide I of protein 
– – 1,469.95 – – – 1,453.95 C-H Scissoring and bending for methylene 
– – – – – – 1,119.71 C-O Stretching due to ether 
– – 1,002.54 – 1,004.05 1,037.18 1,061.10 C-O Stretching due to ether group 
– – 763.42 – – 755.95 798.13 C-H Rocking 

aSample A: 0.2 g MOCP in CMP; Sample B: 0.4 g MOCP in CMP; Sample C: 0.6 g MOCP in CMP; Sample D: 0.8 g MOCP in CMP; Sample E: 1 g MOCP in CMP; Sample F: CMP; Sample G: MOCP.

XRD analysis

XRD measurement was carried out on CMP before treatment (sample F) and after treatment (sample E) with 1 g MOCP serum to characterize and investigate the adsorption of MOCP onto the CMP. The diffractograms obtained from the analysis and the d-spacing measurements of the crystallite showing the strongest peaks observed are presented in Figures 8 and 9 and Table 2, respectively.
Table 2

XRD data of strongest peaks

Sample 2Theta (deg) d-Spacing (Å) 
Sample E 24.1128 3.68786 
24.9137 3.57109 
18.3609 4.82812 
Sample F 24.0255 3.70106 
18.2975 4.84471 
47.5500 1.91072 
Sample 2Theta (deg) d-Spacing (Å) 
Sample E 24.1128 3.68786 
24.9137 3.57109 
18.3609 4.82812 
Sample F 24.0255 3.70106 
18.2975 4.84471 
47.5500 1.91072 
Figure 8

X-ray diffractogram of CMP.

Figure 8

X-ray diffractogram of CMP.

Figure 9

X-ray diffractogram of CMP treated with 1 g MOCP solution.

Figure 9

X-ray diffractogram of CMP treated with 1 g MOCP solution.

From the diffractograms (Figures 8 and 9) and Table 2, sample E (CMP treated with 1 g MOCP serum) showed prominent peaks with d-spacing of 4.82812 Å, 3.68786 Å and 3.57109 Å as compared to sample F (CMP before treatment), which showed d-spacing of 4.84471 Å, 3.70106 Å and 1.91072 Å. It is evident that the perpendicular separation of the crystallites corresponding to the d-spacing is greater in sample F than in sample E, indicating a change in the morphology of the CMP when treated with 1 g MOCP. A negative change in the d-spacing of sample E could indicate organic treatment decomposition on the interlayer space, a loss of organic component or change in conformation of the organic treatment in the composite system rather than in the CMP surface (Cohen et al. 2005). The apparent increase in the d-spacing of sample E, as compared to sample F, as observed for the third strongest peak for each sample, indicates that intercalation may have occurred at such regions and also that ordered clay stacks, large enough to diffract, are still present in the formulated composite system.

Flocculation efficiency of MOCP/CMP composite systems

The MOCP-treated CMP samples, as well as an untreated CMP sample and MOSP sample, were used to treat synthetic turbid water prepared from kaolin and the flocculation activity of each product studied by measuring absorbance of each sample's supernatant water was measured at varied time intervals, and the maximum wavelength (λmax) was determined for each sample. Results are shown in Figure 10.
Figure 10

Effect of time on flocculation efficiency.

Figure 10

Effect of time on flocculation efficiency.

M. oleifera showed the highest rate of flocculation (94.60%) after 1.5 hour of flocculation time and clay treated with 0.2 g MOCP had the lowest rate of flocculation (84.30%) after 1.5 hour. When the flocculation time was extended to 24 hour, at a wavelength of 250 nm, the flocculation efficiency increased for all samples and the flocculants can be classified in order of decreasing efficiency: CMP + 1.0 g MOCP > MOSP > CMP + 0.6 g MOCP > CMP + 0.8 g MOCP > CMP + 0.4 g MOCP > CMP + 0.2 g MOCP > CMP (Table 3).

Table 3

Flocculation activity of MOCP/CMP composite systems

  Wavelength (λmax)
 
Absorbance
 
Flocculation efficiency (%)
 
Product Initial Final After 1.5 hours After 24 hours After 1.5 hours After 24 hours 
MOSP 290.0 254.0 0.034 0.003 94.60 99.52 
CMP 244.0 213.0 0.085 0.040 86.50 93.65 
CMP + 0.2 g MOCP 324.0 209.0 0.143 0.013 84.30 97.93 
CMP + 0.4 g MOCP 322.0 204.0 0.075 0.009 88.09 98.57 
CMP + 0.6 g MOCP 227.0 199.0 0.045 0.003 92.85 99.52 
CMP + 0.8 g MOCP 234.0 216.0 0.065 0.004 89.68 99.34 
CMP + 1 g MOCP 217.0 200.0 0.046 0.001 92.69 99.84 
  Wavelength (λmax)
 
Absorbance
 
Flocculation efficiency (%)
 
Product Initial Final After 1.5 hours After 24 hours After 1.5 hours After 24 hours 
MOSP 290.0 254.0 0.034 0.003 94.60 99.52 
CMP 244.0 213.0 0.085 0.040 86.50 93.65 
CMP + 0.2 g MOCP 324.0 209.0 0.143 0.013 84.30 97.93 
CMP + 0.4 g MOCP 322.0 204.0 0.075 0.009 88.09 98.57 
CMP + 0.6 g MOCP 227.0 199.0 0.045 0.003 92.85 99.52 
CMP + 0.8 g MOCP 234.0 216.0 0.065 0.004 89.68 99.34 
CMP + 1 g MOCP 217.0 200.0 0.046 0.001 92.69 99.84 

Clay treated with 1 g MOCP showed the highest rate of flocculation (99.84%), while the lowest rate of flocculation (93.65%) was with untreated clay. These results are in agreement with values reported in the literature for M. oleifera stating that removal of suspended solids falls within the range of 80–99% for both raw and synthetic turbid water (Ndabigengesere et al. 1995). It is evident that flocculation efficiency increases with increase in the amount of MOCP incorporated onto CMP. CMP + 1.0 g MOCP has the highest flocculation efficiency probably due to the fact that the MOCP content is the highest and, from the literature, it is clear that the protein-rich content of MOCP is the key facilitator of flocculation through the protonation of amine functional groups present. The MOCP adsorbed onto the CMP may have intercalated leading to accumulation of the polyelectrolyte on clay/solution interfaces and, since the protein still retains its conformation, electrostatic neutralization occurs. CMP acts as an anchor; based on its denser particle size, which increases binding sites; hence, for suspended particles converted to flocs at this time, greater interaction at a shorter time is achieved. This may have resulted in optimized performance of the product.

The wavelength (λ) at which absorbance is greatest is shown in Table 3. Knowing this information for a substance is useful, since measurements at this wavelength will be most sensitive. The result indicates shorter wavelengths, as well as a general decrease in the wavelength of the synthetic turbid water after treatment with the various products. This may be due to the greater light interaction with the particles in the cuvette, resulting in a greater reduction in the intensity of transmitted light.

Flocculants that give high flocculation efficiencies at shorter wavelengths, as seen in Table 3, are likely to be more acceptable because they give a better representation of the turbidity of the supernatant. This may be due to the fact that they have more interaction time with particles in the turbid water. This is in agreement with findings reported by Alang et al. (2011).

Samples A (treated with 0.2 g MOCP) and F (untreated) show the highest absorbance values at initial interaction with turbid water. The flocculation profile for CMP treated with MOCP at different concentrations shows a general downward trend for all samples, such that the absorbance decreased with longer interaction and settlement times of the supernatant serum. This implies that the flocculation efficiency improved with longer interaction time. Water clarification generally occurs via two major steps: the first involves interaction of flocculants with turbid water, which results in the formation of flocs through various flocculation mechanisms, and the second involves settling of the flocs by gravity with concomitant water clarification. Therefore, longer interaction time leads to formation of stable flocs and greater settlement of more flocs under gravity, even lighter ones; hence, more clarification of supernatant water (Pernitsky 2003).

Conductivity measurement

Adsorption of MOCP onto CMP was also determined by carrying out conductivity measurements of the samples after resuspending in solutions of various ionic strengths. The polyelectrolyte is generally adsorbed onto clay through pure electrostatic interactions (electrosorption) between the cationic group on the polyelectrolyte and the negatively charged sites at the clay mineral surface. Figure 11 depicts the degree of adsorption of MOCP onto CMP. There is an initial increase in conductivity with increasing ionic concentration to a maximum in 0.8 M NaCl concentration after which it decreased in 1 M NaCl. The initial increase in electrolyte concentration acts to coil the polyelectrolyte. This, in combination with the porous nature of the clay, means that a greater surface area is available to the polyelectrolyte, which gives an increased adsorption. At high electrolyte concentrations, however, the interaction between polyelectrolyte and charged clay surface diminished, resulting in a decrease in the amount adsorbed; hence, the drop in conductivity. This is in agreement with literature as reported for polyelectrolyte adsorption to cellulosic fibres (Gimåker et al. 2007).
Figure 11

Influence of concentration on the amount of MOCP adsorbed onto CMP.

Figure 11

Influence of concentration on the amount of MOCP adsorbed onto CMP.

CONCLUSIONS

In this research, the adsorption of varying concentrations of MOCP onto CMPs surface was studied. The isolation of the proteins and adsorption process was found to have been successful, based on the results obtained from various analytical tests, which included conductivity measurements, FTIR analysis and XRD analysis, as carried out on the formulated microparticle products. These results are consistent with the idea that electrostatic interactions between MOCP and CMP surface may have occurred leading to intercalation of these natural products forming microparticle systems which will allow them to be used as enhanced flocculants for water treatment.

The microparticle products were used to clarify turbid water and flocculation efficiency was analysed using a UV spectrophotometer. The flocculation tests showed that the products possessed exceptional flocculation efficiencies. The accumulation of organic matter which encourages bacterial regrowth and causes fouling of treated water, attendant on the use of MOSP alone for water clarification, is significantly reduced or eliminated when the active ingredient adsorbed onto clay is used.

It is, therefore, evident that the synergy of these natural, locally sourced and readily available products (clay and M. oleifera) forms an effective composite product for water clarification that is low-cost and has no adverse effect on humans and the environment.

REFERENCES

REFERENCES
Alang
M. B.
Barminas
J. T.
Aliyu
B. A.
Usaku
R.
Samuel
A. E.
2011
Comparative studies on the flocculation efficiencies of Moringa oleifera (MO), polyacrylamide grafted gum Arabic (GA-g-PAAM) and blended products of MO and PA-g-PAAM
.
Int. J. Biol. Chem. Sci.
5
,
2140
2154
.
Ali
E. N.
Muyibi
S. A.
Salleh
H. M.
Salleh
M. M.
Alam
M. Z.
2009
Moringa oleifera seeds as natural coagulant for water treatment
. In:
Proceedings of the 13th International Water Technology Conference, IWTC, 13
,
Hurghada
,
Egypt
, pp.
163
168
.
Ali
E. N.
Muyibi
S. A.
Salleh
H. M.
Salleh
M. M.
Alam
M. Z.
2010a
Production of natural coagulant from Moringa oleifera seeds for application in treatment of low turbidity water
.
J. Water Resour. Protect.
2
,
259
266
.
Ali
E. N.
Muyibi
S. A.
Salleh
H. M.
Salleh
M. M.
Alam
M. Z.
2010b
Production technique of natural coagulant from Moringa oleifera seeds
. In:
Proceedings of the 14th International Water Technology Conference, IWTC, 14, 2010
,
Cairo
,
Egypt
. pp.
95
103
.
Berger
M.
2008
Applying Nanotechnology to Water Treatment
.
Nanowerk Spotlight, Nanowerk, LLC.
.
Cohen
J. M.
Lin
T. S.
Morgan
A. B.
Garces
J. M.
2005
Novel synthetic nanocomposite materials and their application in polyolefin based wire and cable compounds
.
The Dow Company, LOES Form No. 31101101
.
Folkard
G. K.
Sutherland
J. P.
Grant
W. D.
1993
Natural coagulants at pilot scale
. In:
Water, Environment and Management: Proceedings of the 18th WEDC Conference, Kathmandu, Nepal, 30 Aug–3 Sept 1992
(
Pickford
J.
ed.).
Loughborough University of Technology Press
,
Loughborough, UK
, pp.
51
54
.
Folkard
G. K.
Sutherland
J.
Shaw
R.
1999
Water clarification using Moringa oleifera seed coagulant
.
Intermediate Technology Publications
,
London
. .
Gimåker
M.
Horvath
A.
Wagberg
I.
2007
Influence of polymeric additives on short-time creep of paper
.
Nord. Pulp Paper Res. J.
22
,
217
227
.
Huda
A. J.
Adolfsen
K. J.
McCullough
L. R.
Velegol
D.
Velegol
S. B.
2012
Antimicrobial sand via adsorption of cationic Moringa oleifera protein
.
Langmuir
28
,
2262
2268
.
Jones
K.
Boxall
C.
Shaw
D.
Buck
M.
McCabe
R.
2007
Nanocomposite for water treatment
.
ECS Trans.
6
,
17
27
.
Moreno
J. M. G.
2009
Application of a Natural Coagulant Derived from Opuntia spp. in Water Treatment
.
European Joint Master in Water and Coastal Management, University of Alicante
, pp.
10
14
. .
Ndabigengesere
A.
Narasiah
K. S.
Talbot
B. G.
1995
Active agents and mechanism of coagulation of turbid waters using Moringa oleifera
.
J. Water Res.
29
,
703
710
.
Pernitsky
D. J.
2003
Coagulation 101. Technology Trans Conference Paper
.
Alberta
,
Canada
.