<font-awesome-icon icon="fa-duotone fa-7" />
<FontAwesomeIcon icon="fa-duotone fa-7" />
.my-icon {
position: relative;
font: var(--fa-font-duotone);
font-style: normal;
}
.my-icon:before {
position: absolute;
content: "\37";
opacity:0.5
}
.my-icon:after {
content: "\37\37";
}
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 320 512" style="width: 30px;height: 30px;fill: black">
<path d="M315.6 80.14l-224 384c-5.953 10.19-16.66 15.88-27.67 15.88c-5.469 0-11.02-1.406-16.09-4.359c-15.27-8.906-20.42-28.5-11.52-43.77l195.9-335.9H32c-17.67 0-32-14.33-32-32s14.33-32 32-32h256c11.45 0 22.05 6.125 27.75 16.06S321.4 70.23 315.6 80.14z"/>
<path style="opacity: 0.5" d=""/>
</svg>
<i class="fa-duotone fa-7"></i>