removal of heavy metals from aqueous environment by low cost adsorption materials rice husk and its ash

VIETNAM GENERAL CONFEDERATION OF LABOUR TON DUC THANG UNIVERSITY FACULTY OF ENVIRONMENT & LABOUR SAFETY TON DUC THANG UNIVERSITY SEMESTER REPORT REMOVAL OF HEAVY METALS FROM AQUEOUS

VIETNAM GENERAL CONFEDERATION OF LABOUR

TON DUC THANG UNIVERSITY FACULTY OF ENVIRONMENT & LABOUR SAFETY

TON DUC THANG UNIVERSITY

SEMESTER REPORT

REMOVAL OF HEAVY METALS FROM AQUEOUS ENVIRONMENT BY

LOW-COST ADSORPTION MATERIALS (RICE

HUSK AND ITS ASH)

Teacher: DR Tran Thi Phuong Quynh

Student: Nguyen Ngoc Minh Thu Student ID :92000152

Class : 20090201

THANH PHO HO CHI MINH, NAM 2023

TABLE OF CONTENTS

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4 Characterizations of rice husk and rice husk ash 5 2 2223221221222 sesk2 6

II USING RICE HUSK TO REMOYVE HEAVY ME,TALL, - < 5 ề5 +<<+ 6

1.1 Treatment of vo ae ằắ 7

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ABSTRACT

Rice husk, which is a relatively abundant and inexpensive material, is currently being investigated as an adsorbent for the removal of heavy metal pollutants from water and wastewaters Heavy metals can be removed very effectively with rice husk as an adsorbent This article presents a brief review on the role of rice husk and rice husk ash in the removal of heavy metal from wastewater Studies on the adsorption of heavy metal by rice husk materials are reviewed and the adsorption mechanism, influencing factors, favorable conditions, etc., discussed in this report It is evident from the review that rice husk and its ash can be potentially utilized for the removal of heavy metal from wastewaters

I INTRODUCTION

1 Heavy Metal

Heavy metals are a group of metals and metalloids that have relatively high density and are toxic even at ppb levels Examples include Pb, As, Hg, Cd, Zn, Ag,

Cu, Fe, Cr, Ni, Pd, and Pt These metals are released into the environment by both natural and anthropogenic sources such as industrial discharge, automobiles exhaust, and mining Unlike organic pollutants, heavy metals are nonbiodegradable and have tendency to accumulate in living beings In fact, most of them are known to be potential carcinogens Various adverse health hazards are known due to long term and continuous exposure to heavy metals Since they are nondegradable and tend to bioaccumulate, suitable methods need to be established for their efficient removal from the environment Guideline values for some of the heavy metals are listed in table(WHO, 2011) (Yadav et al., 2019)

lable I Guideline values of heavy metals

Heavy Metal Guideline Value (mgL~')

2 Effects of heavy metals

2.1 Effects of heavy metal on environment

Heavy metals have a high tendency to form complexes, are highly reactive and have increased biochemical activity which makes them very persistent in the environment They are transported through aqueous medium and can concentrate in soil and water resources This makes them extremely dangerous to all kinds of life forms and the environment Hence, it is necessary to remove these toxic metals from wastewater before discharge to prevent further detrimental consequences

2.2 Effects of heavy metal on Human

In addition to degrading the quality of natural waters, heavy metals can also cause several serious health problems in humans, affecting the nervous system, kidney, liver, and respiratory functions(Shen et al., 2019) Most MTEs are strongly carcinogenic(Shen et al., 2019).Also, MTEs can produce delays in the human growth and development, and disruption of bioregulatory systems responsible for functional or psychosomatic disorders, like chronic fatigue syndrome, and neurodegenerative pathologies, such as the Parkinson’s and Alzheimer’s diseases (Poey and Philibert 2000) Intoxication by some heavy metals, such as mercury and lead, can also lead to autommmunity phenomena, in which the immune system of the patient attacks his own cells This can lead to joint diseases, such as rheumatoid arthritis, and kidney, circulatory, or nervous problems (Tian & Yang, 2007) (Sall et al., 2020)

3 Absortion

3.1 Overview of adsorption process

Adsorption is a surface phenomenon in which a solution containing the adsorbate gets adsorbed on the surface of an adsorbent Adsorption phenomenon can

be of two types; one is physiosorption, in which the adsorbate binds to adsorbent due to van der Waals forces, and other is chemisorption, which occurs due to chemical reactions between adsorbate and adsorbent Physiosorption is reversible, weak and is usually endothermic, while chemisorption is irreversible, selective and exothermic (Tripathi & Ranjan, 2015)

3.2 Adsorption isotherm and models

Adsorption isotherms are representations that estimate the amount the solute that is adsorbed on the surface of the adsorbent per unit weight as a function of equilibrium concentration at a constant temperature The most commonly used are Langmuir and Freundlich isotherms that describe the adsorption process (Langmutr, 1916) Some other models are also used such as Redlich and Peterson (Redlich & Peterson, 1959), Radke and Prausnitz (Radke & Prausnitz, 1972), Sips (Sips, 1948), Toth (Toth, 1971)and Koble and Corrigan.(Koble & Corrigan, 1952)

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3.3 Types of adsorbents

Adsorbents are typically classified on the basis of their origin 1.e natural and synthetic Natural adsorbents include clays, minerals, charcoal, ores and zeolites While the synthetic adsorbents are prepared from industrial wastes, agricultural wastes, waste sludge etc

3.4 Removal of heavy metals from wastewater by adsorption

Adsorption is presumed to be an efficient and cost-effective method as compared to other wastewater treatment technologies for heavy metal removal The main advantage this method provides is the production of a high-quality effluent The process of adsorption has an edge over other processes since it is an economic method for heavy metal remediation In most cases, the adsorbent can be regenerated back and can be used further (Ojedokun & Bello, 2016) Adsorption is easy to use and does not generate any toxic pollutants, hence it is an environment friendly technique (Demirbas, 2008) The prominent criteria of selection of adsorbents include their cost effectiveness, high surface area and porosity, distribution of functional groups and their polarity (Vunain set al, 2016), (Ewecharoen et al., 2009) Conventional and commercial adsorbents comprise of activated carbon, zeolites, graphenes and fullerenes and carbon nanotubes Carbons and their derivatives are the most prominently used adsorbents due their great adsorption efficiency Their exceptional ability comes from their structural characteristics giving them a large surface area with easy chemical modifications which makes them universally acceptable to a wide spectrum of pollutants (Crini et al., 2019) The activated carbons suffer from a few flaws which makes their use quite limited They are expensive to manufacture; the spent activated carbon 1s difficult to dispose and their regeneration is cumbersome and not economical Thus, there was extensive research in the area of low-cost adsorbents The non-conventional adsorbents are cheap, abundantly available and have great complexing capacity due to their varied structure which binds the pollutant ions They range from agricultural waste to industrial waste sludge and spent slurry (Crini, 2010),(Crini et al., 2018)

4 Characterizations of rice husk and rice husk ash

4.1 Characterizations of RH

RH is the hard shell covering paddy rice seed, which provides nutrients and metabolite accumulations during grain development, and protects seeds from physical damage and attacks by pathogens, insects, and pests RH comprises two major, modified, leaf-like structures called the lemma and palea, which completely encase the caryopsis The structured layers of RH are divided into four categories, namely (1) the rough outer epidermis with surface hairs, where the silica is highly concentrated; (2) sclerenchyma; (3) spongy parenchyma cells; and (4) inner

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epidermis, whose surface is relatively smooth and free of hair (Champagne et al., 2004)

4.2 Characterizations of RHA

RHA is a general term describing all types of ash produced by combustion of

RH When RH is incinerated, it produces 17%-20% of RHA, which is a lightweight, bulky, and highly porous material with a density of around 180-200 kg/m3 There are two types of RHA, that is, white rice husk ash (WRHA) and black rice husk ash (BRHA), depending on whether the combustion is complete or incomplete (Ugheoke & Mamat, 2012) The controlled combustion of RH in the atmosphere can lead to production of WRHA containing almost pure silica (>95%) in a hydrated amorphous form with high porosity and reactivity (Vlaev et al., 2003) The controlled pyrolysis of RH in nitrogen or inert atmosphere results in production of BRHA containing different amounts of carbon and silica (Ghaly & Mansaray, 1999)

IL USING RICE HUSK TO REMOVE HEAVY METAL

Adsorption behaviour of Ni(II), Zn(ID, CddI) and Cr(VI) on untreated and phosphate-treated rice husk (PRH) showed that adsorption of Ni(II) and Cd(ID was greater when PRH was used as an adsorbent Sorption of Cd(II) was dependent on contact time, concentration, temperature, adsorbent doses and pH of the solution The Langmuir constants and thermodynamic parameters have been calculated at different temperatures It was found that recovery of Cd(II) from synthetic wastewater by column operation was better than a batch process.(Ajmal et al., 2003)

1 Methods

1.1 Treatment of rice husk

Rice husk was obtained from a local mill, sieved (50— 60 mesh) size, washed several times with distilled water, dried at 60 C for 2 h and preserved at room temperature Five gram dried-husk was treated with 100 ml of 1.0 M K2HPO4 for

24 h The mixture was filtered and washed several times with distilled water to remove the excess phosphate from the treated husk The filtrate was tested for PO3 4 ions by the standard method The resultant adsorbent was finally dried at 70 C for 2

h and preserved at room temperature in a sealed bottle All the chemicals used were

of analytical grade Stock solutions (1000 mg 11) of different metal ions were prepared in distilled water using their nitrates

- washing with distilled water

-

drying in an oven at about 60 °C for 2h

5g dried-husk was treated with 100ml

of 1M K2HPO4 for 24h

‡

washed several times with distilled water

4 dried at 70 C for 2h

*

preserved at room temperature in a sealed bottle

2 Results and discussion

2.1 Effect of concentration

Percent adsorption decreased while metal uptake per unit weight of adsorbent increased as the initial Cd(ID) concentration increased from 10 to 50 mg 11 and after that percentage adsorption became constant

2.2 Effect of contact time

The adsorption of Cd(II) increased with increasing contact time and became almost constant after 60 min

2.3 Adsorption dynamics

The rate constants of adsorption and pore diffusion of Cd(II) were determined

at 20 C using Lagergren (1898) and Weber and Morris (1962) equations, respectively A straight line of log (ge - q) vs t indicated the applicability of the Lagergren equation The plot of Ct=CO vs t 1=2 was linear for a wide range of contact periods but did not pass through the origin, indicating that pore diffusion was not the only rate-controlling step (Poots et al., 1978)

2.4 Isotherm studies

The related parameters of Langmuir isotherms at different temperatures are summarized in Table 1 The Langmuir isotherm is obeyed better than the Freundlich

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isotherm as is evident from the values of regression coefficients The adsorption of Cd(11) increased with increase in temperature The Langmuir model is an indication

of surface homogeneity of the adsorbent The thermodynamic parameters, DGO, DSO and DHO are reported in Table 2

Table 1

Langmuir constants at different temperature

Temperature Langmuir constants

R Ø° (mgg}) b (Img"')

20 0.994 103.09 0.006

30 0.923 1666.66 0.0039

40 0.93 2000.00 0.0038

Table 2

Thermodynamic parameters for adsorption of Cd(II)

Temper- K AG’ AH® As°

ature (°C) (kcalmol') (kcalmol') (kcal K~' mol~')

20 1.702 —0.311

30 2.680 —0.5973 +9.511 0.033

40 4.550 —0.948

5

4.5 a

4 +

3.5 3

° 0°

x

a

1.5 4

14

0.5 4

1/T

Fig 1 Plot of log K versus 1/T

100 3

80 4

60 4

40 1

20 4

Fig 2 Effect of pH on the adsorption of Cd(II) by rice husk

> The ability of rice husk to adsorb Cd(II) from water has been explored The extent of removal depended on concentration of the solution, pH, temperature and contact time The adsorption process followed the Langmuir isotherm The process was endothermic in nature The results showed that rice husk might have been successfully used as an adsorbent for the removal of Cd(II) from wastewater Removal efficiency by column process was better than by batch process

Ill USING RICE HUSK ASH TO REMOVE HEAVY METAL

To remove heavy metals, they used the electrospinning technique and in situ polymerization methods to produce a polymethylmethacrylate(nce husk ash)/polypyrrole (PMMA/RHA/PPy) composite membrane that can act as a low-cost and efficient adsorbent material for water remediation In these composite systems, while the incorporation of RHA on the PMMA fibers leads to reinforced membranes, the conducting polymer plays the active role of mteracting with the contaminants We tested the performance of the PMMA/RHA/PPy membranes in the removal of Cr(VI),

a heavy metal ion, and the organic dyes tartrazine (E102) and indigo carmine (IC) dissolved in aqueous media We choose these compounds as representative examples of the contaminants usually found in water bodies(da Rocha et al., 2020)

1 Materials and methods

1.1 Materials

We acquired dimethylformamide (DMF - HCON(CH3)2), iron CIID) chloride hexahydrate, hydrochloric acid (HCI), tartrazine (C16H9INa30982) and indigo carmine (CI6H8N2Na20882) from Dinamica (Brazil), and poly- “ methylmethacrylate (PMMA), sodium dodecyl sulfate (SDS) and pyrrole from Sigma Aldrich (USA) Rice husk was obtained from the Company "Amo flor de cera" (Brazil), and potassium dichromate (K2Cr207) from Quimex (Brazil) We used all reagents without further purification, except pyrrole, which was distilled under vacuum before use In all experiments, we used deionized water obtained after passage through a Millipore Synergy ultra-purification system

1.2 Preparation of adsorbent membranes

The rice husk was washed with deionized water to remove impurities and subsequently dried and charred at 1000 °C for 3 hin a 1200 SP LABOR (Brazil) muffle furnace Afterward, we macerated the ashes and prepared solutions with different proportions (1:0.1, 1:0.2, 1:0.5 and 1:0.8) of PMMA/RHA in the following manner (Scheme |): 1) initially, we used DMF to prepare the RHA solutions, which we then submitted to ultra-sonication for 30 min to promote the dispersion of the particles

We added the PMMA to the solutions and placed them on a stirring plate at 40 °C, under magnetic stirring for 24 h; 11) we then placed 2 mL of the PMMA/RHA solution

in a3 mL plastic syringe coupled to a stainless steel needle, connected to a horizontal electrospinning system We adopted a flow of 0.5 mL/h, as controlled by a NE-4000 (New Era, USA) pump, and a working distance of 20 cm between the needle tip and the grounded collector, under a constant voltage of 17 kV; 111) afterward, we prepared a sandwich structure of alternating aluminum sheets (four) and membranes (three) that was submitted to a 100 °C heat treatment for 48 h in an oven, under a weight of 1 kg; iv) after cutting the membranes in the form of 0.02 m2 squares, we treated them in a PDC-002 (Harrick, USA) air plasma system for 3 min, and finally modified them by the incorporation of polypyrrole prepared via an in situ chemical polymerization (da Rocha et al., 2020)

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