Heavy sorbents in this discipline are normally based

     Heavy metal ions infection in water has to turn out to be an international
environmental subject and trouble. Mining operations, tanneries, batteries manufacturing,
microelectronics, and petrochemical industries are the predominant assets for
heavy metal ions contamination in water. These metal ions in excess quantity
are dangerous to human and biological system because of their toxicity and accumulation
within the flora and body. The metal finishing industries and electroplating
are in particular accountable for Cu(II) contamination in water. Cu(II) makes
keratinization, a dramatization of fingers, and itching. The kidney dysfunction and severe gastrointestinal irritation are
come about because of the immoderate consumption of Cu(II). Inhalation of
copper spray expands the threat of lung cancer in exposed individuals 1-3. Ni(II)
has widely existed in surface water, and even in drinking water, discharging from
cadmium-nickel batteries, phosphate fertilizers, pigments, sewage sludge and alloy
industries. Nickel in extra quantity creates emphysema, and high blood pressure
4,5.

          Various
technologies had been carried out for heavy metallic containing wastewater remedy,
consisting of electrocoagulation, chemical precipitation, ion-exchange, and so forth. Amongst these, adsorption strategy is broadly
carried out because of excessive performance, low operation
costs, and smooth
operation 6-8.

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          Microwave-enforced
sorption (MES) method for extraction and expulsion of heavy metals from real
water samples. This system is recommended to work by the relocation of the adsorbate from solution and
adsorption on the sorbent surface in a couple of moments “seconds” affected by
microwave warming illumination to build up a harmony condition 9,10. This
system is working in the invert heading of the microwave-assisted extraction (MAE)
process 11. This
strategy is critical to green and economical chemistry as it can expand
productivity, upgrade wellbeing in a few different ways enhancing yields, and
to take out or keep away from waste generation through cleaner handling.

          In
most recent years, opportunity innovations utilizing
nanomaterials have attracted enormous interest in natural remediation. The recently applied and implemented sorbents
in this discipline are normally based on low cost substances 12, polymeric
compounds 13,14 as well as nanostructured metal oxide derivatives 15,16 .

          Reduced
glutathione (GSH, (?-Glu-Cys-Gly)), it plays a vital part in human body by (1)
preventing damage to critical cell parts caused by reactive oxygen species such
as free radicals, lipid peroxides, and heavy metals. (2) It keeps up
levels of reduced glutathione peroxidase and glutaredoxin (3) maintaining
exogenous cancer prevention agents, for example, vitamins C and E in their
reduced (active) forms.(4)It has an ability to maintain sulfhydryl groups of
proteins in the reduced form and keep up thiol redox potential in cells. From
the spearheading work, it is understood that GSH can adequately secure natural
cells from the troublesome impacts that start from oxidizing substances,
dangerous substances and radiation harm 17,18. In view of the literature
survey, some research works have been centered around GSH uses in different
fields of chemistry, for example, utilizing glutathione-stabilized gold
clusters (GSH-Au NCs) as a fluorescent probe for selective determination of
Cr(III) and Cr(VI) 19. Glutathione-based nano-organocatalyst for
microwave-assisted pyrazole, Paal–Knorr reaction and aza-Michael addition
synthesis in water20. Reduced glutathione functionalized iron oxide
nanoparticles for magnetic removal of Pb(II) from wastewater21.Here, The utilization of glutathione (over other amino
acids) as a dynamic catalytic moiety is
favored because of its considerate nature and also  the nearness of the exceedingly unique thiol
gathering.The N-Si was arranged by sono-chemical covalent bonding of
glutathione atoms through coupling of its thiol group with the free hydroxyl  groups of nanosrbent surfaces.

In
this work, (1) GSH was used as surface modifying agent for N-Si surface by  sonochemical reaction to produce N-Si-Glu.(2)
immobilize  the surface of N-Si  with glycine via glutaraldehyde  as a crosslinking agent for the preparation
of N-Si-Gly.(3)Compare  results of  the two nanosobents and optimization of the
MES technique as green and effient protocol in
removal of Ni(II),Cu(II),Cd(II), and pb(II) from real samples under different
test controlling parameters.

2. Experimental

2.1. Characterization
of N-Si-Glu and N-Si-Gly

         Thermal gravimetric analysis (TGA) of nanosilica and the
other immobilized
sorbents were examined by utilizing
a Perkin–Elmer TGA7
Thermobalance. The selected
operating conditions were the
temperature heating range = 20–600 oC, heating rate = 10 oC
min-1, flow rate = 20 mL min-1 pure nitrogen atmosphere
and the sample mass was taken in the range of 5.0–6.0 mg.The FT-IR spectra of nanosilica and immobilized
nanosilica sorbents were recorded from KBr pellets by using a
BRUKER Vertex 70 Fourier transform infrared spectrophotometer in the range of
400–4000 cm-1. SEM,
(JSM-6360LA, JEOL Ltd.), (JSM-5300, JEOL Ltd.), 
an ion sputtering coating device (JEOL-JFC-1100E) and HR- TEM images were taken by a (JEOL-JEM2100F, Japan) at 200 kV were used to examine the
surface morphology and determine the particle size of all nano-silica sorbents.

The
crystalline structure of the sorbents was inspected utilizing X-ray diffraction (XRD) examination by Shimadzu XRD-6100, X-ray
diffractometer utilizing target Cu-K?. Surface area analysis was performed
by using (BELSORP –miniII nitrogen physisorption, Japan) in order to measure the surface
area of nano-sorbents.The concentration of analyzed metals were dictated by utilizing a Perkin Elmer atomic absorption
spectrophotometer, model 2380.

2.2. Materials

         Nanosilica
(10-20 nm), L-Glutathione reduced (F.W. 307.32) were purchased from Aldrich
Chemical Company, Milwaukee, WI, USA. Different concentrations of Ni(II),Cu(II),
Cd(II) and Pb(II) solutions were prepared from a stock solution of (0.01 M) by dissolving
3.5891 g of Ni(SO4)2.6H2O,17.048 g of CuCl2.2H2O,
1.005g of CdCl2
and 3.3121 g of Pb(CH3COO)2.3H2O,
respectively in DDW to form 1.0 L solution and the accurate concentrations of these
ions were examined by complexometric
titration with standard 0.01 M EDTA utilizing the appropriate buffer and
indicator.

2.3. Functionalization
of NSi with glycine

         Nanosilica sorbent was activated
following the protocol previously described by our group16. Adding 2.0 g
of glycine, 150 mL ethanol, and 7 mL
of glutaraldehyde was mixed with 2.0 g of activated nanosilica. This mixture
was refluxed for 12 h. The produced nanosorbent(N-Si-Gly)
was then separated by filtration washed
with water and ethanol, and dried in oven at 60?C.

2.4.
Anchoring of glutathione (reduced form) on nanoSilica sorbent

          3 g activated (N-Si) was dispersed in
(30 mL ethanol+90 mL DDW) and sonicated for 20 min. 2.4 g L-Glutathione
reduced form dissolved in 30 mL DDW was mixed
with this solution and again sonicated for 2 h. This mixture was stirred for 12
h at room temperature. Then the glutathione-functionalized nanosilica
(N-Si-Glu) was isolated by centrifugation at 15,000 rpm for 20 min and purified
through triplet washes with (75 mL of ethanol+25 mL DDW) and dried under vacuum.

2.5.
MES of four analyzed metals by N- Si-Gly
and N- Si-Glu

2.5.1.
Heating time effect on the MES values

          10.0±1.0
mg of the selected nanosorbent,
(N-Si-Gly) and (N-Si-Glu) was transferred in a test tube and mixed with a 10.0
mL aliquot of 0.01 M divalent metal ion. This mixture was heated for the
selected time period (5.0, 10.0, 15.0, 20.0 and 25.0 s) inside a microwave oven
at 800 W. The reaction mixture was filtered and washed with 50 mL DDW. This procedure was repeated 3X and the remaining ions in the
filtrate from each experiment were examined by EDTA titration and the metallic capacity was computed
from Eq. (1).

             (1)

 Whereas Co and C= beginning and remaining metal ion
concentration(M), V= aqueous volume of the sorption reaction, m= mass of dry
nanosilica sorbent in gram and q (?molg?1) is the metallic capacity
that represents the amount of adsorbed divalent metal ion (?mol) per gram of
dry nanosilica sorbent.

2.5.2.  pH effect  on the MES values

The
pH effect on the MES values of Ni(II), Cu(II),Cd(II) and Pb(II) by (N-Si-Gly)
and (N-Si-Glu) was also investigated by adjusting the pH value of the test metal ions  in
the range 1 – 7 utilizing either 1 M HCl or NaOH solutions.  A 10 mL aliquot of the pH-adjusted metal was subjected to heat in the microwave
oven for a 15 sec. The unextracted metal ion was determined as
described above.

2.5.3. nanosorbents dosage effect on the MES values     

Comparative
investigations were completed by utilizing various nanosorbent masses (5.0,
10.0, 15.0, 20.0, 30.0, 40.0, 50.0 and 60.0 mg). The chosen mass of modified
nanosilica sorbent was blended
with 10 mL of 0.01 M
metal utilizing the optimum pH for each divalent metal and heated inside the
microwave oven for 15.0 sec utilizing 800 W. The
metallic capacity was measured in 3X by titration against EDTA according to Eq.
(1).

2.5.4. Initial metal ion
concentration effect on the MES values      

          The sorption procedure was investigated utilizing
10.0±1.0 mg of nanosilica sorbent with various metal concentrations in the
scope of 0.005-0.01 M
utilizing the ideal
conditions as indicated in 2.5.3.

2.5.5. Coexisting
ions effect on the MES values

         The
examined solutions were set
up by combining
a 10.0 mL aliquot of 0.01 M of metal ion
and 100±1.0 mg of the competing species (NaCl, KCl, CaCl2, NH4Cl
and MgSO4) at the optimum pH. The sorption mixture was heated for
15.0 sec inside a microwave oven at 800 W. The remaining metal ion concentration was assessed in triplicate by
EDTA titration as portrayed
previously. On
account of CaCl2 and MgSO4 as the competing
species, the remaining concentrations of Pb(II) and Cd(II) were dictated by Perkin Elmer A.A., while Hg(II) was evaluated by utilizing a UV-Vis spectrophotometer. For effective correlation, the metal sorption limit estimations were also investigated and assessed in
the absence of the coexisting ion.